: Why No Run-flat Tires?



JFJr
01-25-09, 09:40 PM
I was shocked to discover that my 2009 CTS-V did not come with run-flats, as my 2005 did. Other than attempting to keep the cost of the car down, I can think of no other good reason not to have made them standard. To me this is a step backwards in technology. I have no interest in racing such a nice car, so the usual arguments about the superior ride and handling of non-run-flats don't impress me. I have been told that the stock wheels are compatable with run-flats and that the Michelin run-flats are now available. Anyone else have any thoughts on this?

Aron9000
01-25-09, 09:44 PM
Runflat tires ride stiffer, are signficantly noisier, and do not have as much grip. Consider it a blessing IMO, my buddy switched from Goodyear runflats to BFG KDW's on his 2006 Corvette when he changed wheels. It was a night and day difference in terms of noise and ride quality, and that's from riding shotgun.

And when was the last time you got stranded from a flat tire?

Luna.
01-25-09, 09:50 PM
I was shocked to discover that my 2009 CTS-V did not come with run-flats, as my 2005 did. Other than attempting to keep the cost of the car down, I can think of no other good reason not to have made them standard. To me this is a step backwards in technology. I have no interest in racing such a nice car, so the usual arguments about the superior ride and handling of non-run-flats don't impress me. I have been told that the stock wheels are compatable with run-flats and that the Michelin run-flats are now available. Anyone else have any thoughts on this?

I tend to agree.

Last I left off though, there were no run-flats bigger than 275s, but maybe there is based on your comment above?? :confused:

And I'm not sure I agree that runflats don't have very good grip--they had very good grip on the first generation Vs, so good in fact that people were switching from them to help with wheel hop

Razorecko
01-25-09, 09:51 PM
The only real benefit of runflats is having a blowout at highway speed. I've had a blowout at 70mph before and the sh*t is not fun. With a runflat your sensor will go off and you can just cruise at 50mph to the nearest runlfat tire shop.

caddiedrummer
01-25-09, 09:52 PM
Run craps as many call them one day may be good but they are awful now. My 06 Viper had them then there were so many issues they gave up and went to PS2s as on the Caddy.Even the Hondas (minivans) have had problems with them

They do give some piece of mind but if you are out of town good luck finding someone who can replace the tires that come on your V or Viper within 50 or 100 miles anyway. I just keep a can in the car.

JFJr
01-25-09, 09:55 PM
My Cadillac dealer told me that the tires are available in the correct size. I could care less about extra noise or harder ride if, in fact, that really is the case.

Razorecko
01-25-09, 09:56 PM
^ Actually there are two kinds of runflats from what i know. The ones that have the support at the sidewalls and the ones that have the support on the tread. Supposadly the ones that have the tread support barely even feel stiffer than a non runflat. I do know that the sidewall runflat's are obvsiously stiffer since they would proved alot less flex than either.

Razorecko
01-25-09, 10:04 PM
Taken from tirerack...

Auxiliary Supported Run Flat Systems

Auxiliary supported systems combine unique wheels and tires used for Original Equipment vehicle applications. In these systems, the flat tire's tread rests on a support ring attached to the wheel when the tire loses pressure. The advantage to this type of system is that it will place most of the mechanical task of providing run flat capability on the wheel (which typically doesn't wear out or need to be replaced), and minimizes the responsibility of the tire (which does periodically wear out and requires replacement). Additionally, auxiliary support systems promise better ride quality because their sidewall's stiffness can be equivalent to today's standard tires. The disadvantage to auxiliary supported systems is that their unique wheels will not accept standard tires and that their lower volume will make this type of system more expensive.

http://www.michelinman.com/pax/

GM-4-LIFE
01-25-09, 11:39 PM
I am glad to have the PS2 non-run flats! The ride quality, handling and comfort levels are much better compared to every other GM vehicle I have owned with run-flat tires.

If I get a flat, I will handle it!

SG

Ketzer
01-26-09, 10:03 AM
We also have a Cooper S. JCW wheels with runflats. My wife insisted on these for the whole piece-of-mind deal. About a month ago she had the low pressure warning come on and the car started feeling wonky. She pulled into a gas station to see if adding some air might help her get it over to BMW. The tire was visably flat (impossible I know, its a runflat), the tire bead had seperated from the rim. She was trapped waiting for a rollback. Luckily this happened in the city.

Moral to the story, what security did they provide? We will not be using runcraps again.

CIWS
01-26-09, 10:24 AM
Is there even a manufacturer who makes a set of run flats in the stock OEM size ? I looked right before the car was released (Oct) and no one did then.

jvp
01-26-09, 10:25 AM
The tire was visably flat (impossible I know, its a runflat), the tire bead had seperated from the rim. She was trapped waiting for a rollback. Luckily this happened in the city.


Um, what kind of runflats did you have on that car? I've used runflats on every Corvette I've had since my 96. I've never had anything like that happen when they picked up a nail or otherwise got deflated.

FWIW: I'd rather there be runflats on the car, personally. I've had to make use of them a couple of times in the past. If I need super-sticky handling, I'll get the R compounds out.

jas

Razorecko
01-26-09, 11:53 AM
^ agreed. I've had a hex bolt stuck in my runflat for 4 days as I waited for my backordered tire to come in. For mainly street driving I would go non-runflat. For the big highway drivers like myself I'd have to lean towards the security of a runflat. If the bead broke on a non runflat tire you would probally end up having to replace the rim also from the damage it would incur.

Ketzer
01-26-09, 02:31 PM
Um, what kind of runflats did you have on that car? I've used runflats on every Corvette I've had since my 96. I've never had anything like that happen when they picked up a nail or otherwise got deflated.

FWIW: I'd rather there be runflats on the car, personally. I've had to make use of them a couple of times in the past. If I need super-sticky handling, I'll get the R compounds out.

jas

Dunlop SP Sport DSST 205/40/18
This is a common discussion on the Mini forums, same arguments, same expert opinions. Most of those folks are ditching the runflats altogether. There are only a few die hards that insist they "must" have them for the "safety" aspect. One or two even said they liked the hard ass sidewall for the performance it provided. Not just any tire shop will even fool with them. They are not to be plugged. Lucky we bought the road hazard, this was the fourth time to be repaired... in 20k miles... and the tires are shot, need to be replaced.

Jeff-

tedcmiller
01-26-09, 03:00 PM
1. It is true that the 2009 CTS-V does not come with run-flat tires.
2. No one at this time makes run-flat tires in the same service grade and size as provided on the 2009 CTS-V.
3. While run-flats are stiffer and do not ride as comfortably as non-run-flats, I would rather have them for the security.
3. Run-flat tires that do not perform as run-flat tires are either not run-flats or are poor tires. I have had four sets of run-flats in both Goodyear and Bridgestone on my 2004 and 2005 CTS-V and got exactly that performance predicted. I love them.
4. In a few years all new cars will be required to have run-flats as mandated by the Feds. Get used to them.
5. As stated by several responders, not all tire shops know how to deal with or are willing to work with run-flats. That is why I have all my tire work done by the dealer.
6. They can be plugged and will perform just as well as before. Plugged tires of any kind can have problems, but as long as they are run at reduced service levels, they are fine.
7. The run-flat technology that supports the tire internally rather than relying upon stiffer sidewalls is implemented in several forms such as the Michelin PAX technology. I personally would rather have a standard stiff side wall run-flat. Michelin calls it Zero Pressure (ZP). Some manufacturers have called it Extended Mobility (EMT).
8. Michelin has informed me directly that ZP tires in the size and service grade needed for the rear of the 2009-CTS-V will be available next year. There is currently no plan to provide equivalent ZP tires for the front of the 2009 CTS-V.

Luna.
01-26-09, 04:04 PM
6. They can be plugged and will perform just as well as before. Plugged tires of any kind can have problems, but as long as they are run at reduced service levels, they are fine.


Be careful here.

Some places will NOT repair a run-flat tire. Oh, they (cough) can and the tire will probably be fine, but they are NOT supposed to, per most manufacturer's guidelines.

I guess the idea is that once the tire has supported the car's weight on the tire, it's now impacted and isn't to be used again.

Ketzer
01-26-09, 04:10 PM
We were told the same thing Luna, once flat, not to be repaired in ANY fashion. How convienient for the tire manufac. Ours has been patched thrice and replaced once.


I'm not saying they aren't a great idea and have their place... I think the tech is lacking and the price is re-dickyou-luss.

JFJr
01-26-09, 04:43 PM
8. Michelin has informed me directly that ZP tires in the size and service grade needed for the rear of the 2009-CTS-V will be available next year. There is currently no plan to provide equivalent ZP tires for the front of the 2009 CTS-V.

If your information is correct, then my Cadillac dealer was mistaken, or vice versa. What I don't understand is why Michelin did not design a set of ZP tires specifically for the 2009 CTS-V before production began. The stock non-run-flat tires were specially designed by Michelin for the car. Was cost an issue or is something else going on? This backwards step in technology is hard to fathom.

jvp
01-26-09, 05:13 PM
The stock non-run-flat tires were specially designed by Michelin for the car. Was cost an issue or is something else going on? This backwards step in technology is hard to fathom.

Well, when manufacturing anything for sale, you have to try to forecast how many units you'll sell. You use this forecast to, firstly, convince your management/capitalists/investors/etc that you can make a profit on it. In other words, your ROI will be relatively high.

Michelin probably doesn't think their ROI would be very high at all. If you look at the number of people in this thread alone that would rather NOT have run-flats... it's a very good representation of what the performance-minded folks think. People generally don't like run-flats. I'm sure Michelin knows this, and they don't want to waste their money on it.

jas

JFJr
01-26-09, 06:04 PM
If you look at the number of people in this thread alone that would rather NOT have run-flats... it's a very good representation of what the performance-minded folks think. People generally don't like run-flats. I'm sure Michelin knows this, and they don't want to waste their money on it.

jas

I certainly don't agree with your generalization about run-flat tires and doubt that anyone would otherwise decline to purchase a 2009 CTS-V if run-flat tires were OEM, but you're entitled to your opinion.

RightTurn
01-26-09, 06:10 PM
What the heck?? Tires are an easy change; just go buy the ones you prefer. Voila', problem solved.

TaVern
01-26-09, 06:26 PM
I got rid of my runflats after this happened to me -->http://www.cadillacforums.com/forums/cadillac-cts-v-series-forum-2004/150143-look-what-i-got-lindsay-cadillac.html#post1638514

jvp
01-26-09, 06:27 PM
I certainly don't agree with your generalization about run-flat tires and doubt that anyone would otherwise decline to purchase a 2009 CTS-V if run-flat tires were OEM, but you're entitled to your opinion.

It's an opinion based on observation, of threads here and at the Corvette Forum. Performance guys just don't like run-flat tires. They don't grip as well as their non run-flat counterparts do. They aren't as comfortable over bumps and ruts as their non run-flat counterparts are. If you look through the various threads on the forums, you'll see people (quickly) swapping the run-flats out for non run-flats. That's not opinion, it's fact.

Michelin didn't make them initially because GM (specifically, the guys at HPVO) didn't want them on the V. They probably won't make them because not enough people would buy them aftermarket.

jas

tedcmiller
01-26-09, 08:56 PM
In response to TaVern, I plugged two run-flats and never had to replace one. True, most tire shops don't carry run-flats, but having to replace one is a rare occurance. If a run-flat needs replacing away from home, buy a much less expensive non-run-flat of the same size and use it until you can get a less expensive (e.g., from Tire Rack) replacement run-flat of the same type.

Speaking of plugging, I agree with Ketzer. The prohibition against plugging tires is money in the manufacturer's or tire shop's pocket. Luna has suggested that a run-flat tire might not be plugged by some tire shops due to the manufacturer's prohibition. My dealer does not question the need for plugging and plugs both kinds of tires. In both cases the "no plug" advocates make money. I have had only one plug fail in over a dozen plugs and that one manifested itself (the hole was too large to start with) as a slow leak. I like run-flats and will use them whenever possible. The security is worth all of the other "problems."

To JFJr: Your dealer is mistaken. They will tell you anything to get you to buy the car. If you don't believe me, try to find the same tire as provided on the 2009 CTS-V in a ZP version on the Michelin web site. As I said in my previous post, Michelin themselves admit that currently there is no ZP version of the 2009 CTS-V tires. If you want to know why, ask Michelin. I believe that the other posters who suggested that the ROI is too low are correct.

JFJr
01-26-09, 09:25 PM
It's an opinion based on observation, of threads here and at the Corvette Forum. Performance guys just don't like run-flat tires. They don't grip as well as their non run-flat counterparts do. They aren't as comfortable over bumps and ruts as their non run-flat counterparts are. If you look through the various threads on the forums, you'll see people (quickly) swapping the run-flats out for non run-flats. That's not opinion, it's fact.

Michelin didn't make them initially because GM (specifically, the guys at HPVO) didn't want them on the V. They probably won't make them because not enough people would buy them aftermarket.

jas

Again, your opinion, not universally shared.

I have owned 6 Corvettes, all but one manual transmission Z-51 cars, and the 1989 - 2001 cars had 6-speed transmissions. The 1995 - 2001 cars had Goodyear run-flats. I have also owned a 2005 CTS-V (it came with run-flats) and own a 2009 CTS-V. I haven't had any problems with run-flats and believe that they are good performers, but don't race my cars. I am interested in the opinions of those who have actually owned high performance cars, not just read about them on forums or car magazine reviews.

The 2009 "V" is a very special car that appeals to a group that appreciates both extreme performance and luxury.

I would like to hear from someone that actually owns a 2009 CTS-V, has a similar background with high performance cars and can relate to where technology is headed.

Luna.
01-26-09, 09:59 PM
Speaking of plugging, I agree with Ketzer. The prohibition against plugging tires is money in the manufacturer's or tire shop's pocket. Luna has suggested that a run-flat tire might not be plugged by some tire shops due to the manufacturer's prohibition. My dealer does not question the need for plugging and plugs both kinds of tires.

Based on what I have been told, from multiple sources, no one is supposed to plug runflats. If they do, I believe they are opening themselves up to risk in the form of a lawsuit if one ever failed, especially if such failure caused a significant accident/injury.

I don't know for certain though...just repeating what I was told.

jvp
01-26-09, 10:32 PM
Again, your opinion, not universally shared.

You have apparently completely missed the point of my posts. I'll try to explain them a bit more clearly; if it still doesn't work then I'll give up.

I like run-flat tires. I personally think the car should come with them. Based on my observations over many years on performance-related car sites (such as the corvetteforum), OTHERS would rather not have them on their cars.

It is a fact that run-flat tires don't perform as well as their non-run-flat counterparts, where all-out grip and tire compliance is concerned. It is a universally accepted opinion that run-flat tires aren't as comfortable to ride on their non-run-flat counterparts.


I have owned 6 Corvettes

So? I've owned three Corvettes since 1996 as well; I still own one. It doesn't make you an expert on anything. Just like it doesn't make me one. What I am capable of doing (which apparently you aren't) is pay attention to what the performance-oriented Corvette (and Caddy) drivers want on their cars. People don't like run-flats because of their harsh ride, and lower performance envelop.

That's not my opinion. That's the collective opinion of a whole bunch of people.

HPVO is made up of hyperly-capable performance-oriented engineers. Moreso than team Corvette is. Team Corvette has some sort of internal rule that the car WILL have run-flats going forward (for whatever reason) as opposed to the can of fix-a-flat. Perhaps that will change in the future, but as it stands now, Vettes are equipped with run-flats. HPVO, on the other hand, was not forced to do the same thing. They were free to experiment with other tire types, and settled on the non-run-flat Michelin for PERFORMANCE reasons.


I am interested in the opinions of those who have actually owned high performance cars, not just read about them on forums or car magazine reviews.

Good grief man, reading comprehension is something we're supposed to be taught early in grade school. Isn't it? Did they teach you reading comprehension when you were in school? Do you understand the words I've written so far in this thread? I'm a Corvette owner, and, when the weather's nice, I actually run at a local race track with it.


I would like to hear from someone that actually owns a 2009 CTS-V, has a similar background with high performance cars and can relate to where technology is headed.

I don't yet own a V, but that doesn't make my knowledge of performance cars (specifically: higher performance than you've owned thus far..) any less than yours. That you choose not to pay attention to what I've written because of some preconceived superiority over me isn't my fault.

Enjoy your car. And your ignorance.

jas

tedcmiller
01-27-09, 12:16 AM
Luna, obviously my dealer is more concerned about customer satisfaction than lawsuits. I still like run-flats and their added security is well worth the potential problems.

For those who might be interested, the closest equivalent tires that I found in sizes matching the 2009 CTS-V tires in run-flats are the Goodyear Eagle F1 GS-D2 EMT 96W for the front and the Goodyear Eagle F1 GS-2 EMT 90Y ($290 at Tire Rack) for the rear. There are a number of problems with the front tire (GS-D2) in that its tread design does not match the GS-2 on the rear, it is apparently available only in Europe (see iTyre), and it has a lower service rating of 96 W. The rear tire has a lower service rating of 90Y. Both tires are reported to be very noisy.

Luna.
01-27-09, 02:48 AM
Luna, obviously my dealer is more concerned about customer satisfaction than lawsuits. I still like run-flats and their added security is well worth the potential problems.


Very good. I wish more dealers were like that. Actually, I wish more people weren't pu$$ies and sue over the stupidest of things, ruining it for the rest of us... :(

Personally, I'm a fan of runflat tires. Is it really true that they don't grip as well? Wow...that's not the issue we had on the V1s, where people were leaving the Goodyears for they were TOO sticky, which many believed helped cause wheelhop.

What size are the tires are you mentioning? I would think a nice set of 295s in the rear would work well with 255s in the front.

Do we have to worry about Stabilitrac/ride height like we did in the V1s when it comes to tires sizes??

tedcmiller
01-27-09, 08:13 PM
I switched from Goodyear F1s (two sets) to Bridgestone RE050s on my 2004 and then moved them (along with the chrome stock wheels) to the 2005 because they provided better mileage, cost less, and seemed to stick just as well. In retrospec I would say that the Goodyear tires provided slightly more traction and the Bridgestones RE050s were directional where the F1s were not (RE050As are not directional). As far as the wheelhop issue was concerned, I didn't try to "burn rubber" on take off because I knew that the CTS-V was not intended to be driven that way. It happened inadvertantly a couple of times, but it was infrequent enough so that it was not an issue as far as I was concerned. Cadillac has supposedly solved the wheelhop problem for the 2009 CTS-V by using different diameter half-shafts in the rear. The statements saying that run-flats don't grip as well as non-run-flats are not, as far as I know, substantiated by test data.

The tires that come on the 2009 CTS-V are 255/40ZR19 96Y in the front and 285/35ZR19 (99Y) in the rear. 295s in the rear, replacing the stock 285s, might be OK if there is enough clearance. Although I prefer the run-flats, I plan to stay with the stock tires (and the compressor/sealer unit) provided until they wear out. Maybe by then, someone (hopefully Michelin) will have come up with run-flat tires that can be used on the 2009 (or later) CTS-V.

JFJr
01-27-09, 09:36 PM
The tires that come on the 2009 CTS-V are 255/40ZR19 96Y in the front and 285/35ZR19 (99Y) in the rear. 295s in the rear, replacing the stock 285s, might be OK if there is enough clearance. Although I prefer the run-flats, I plan to stay with the stock tires (and the compressor/sealer unit) provided until they wear out. Maybe by then, someone (hopefully Michelin) will have come up with run-flat tires that can be used on the 2009 (or later) CTS-V.

My plan, too. I wonder if the GM performance division figured that they needed the stock tires to set a record on the "Ring," because development of the high performance ZP tires was not far enough along for that kind of run. I understand that the current M5 (the benchmark for the 2009 CTS-V) has the same size wheels and same Michelin tires. I believe that we will see some great run-flat, high performance tires become available in the next year for the 2009 CTS-V. You have some good insight, what do you think?

RapidRob
01-27-09, 11:19 PM
The tires that come on the 2009 CTS-V are 255/40ZR19 96Y in the front and 285/35ZR19 (99Y) in the rear. 295s in the rear, replacing the stock 285s, might be OK if there is enough clearance. Although I prefer the run-flats, I plan to stay with the stock tires (and the compressor/sealer unit) provided until they wear out. Maybe by then, someone (hopefully Michelin) will have come up with run-flat tires that can be used on the 2009 (or later) CTS-V.

Slightly off topic but are you sure the stock V2 tires are 255/40ZR19 and 285/35ZR19's? The reason I ask is that the brochure I have that lists the V2's specs show it having 255/40R19 fronts and 285/35R19 rears. The BMW M5, does have the ZR19 tires. I don't have my V2 yet, so I can't actually check it out myself.

Rob

tedcmiller
01-28-09, 12:00 AM
RapidRoger, the tires I describe are the ones that are on my 2009 CTS-V. The numbers are directly from the side of the tire wall, not from some advertising brochure or magazine article. The presence of the Z in the tire size simply indicates that the tire is rated for speeds in excess of 149 mph. The Z designation came about when tires were developed that could go 150 mph or faster. In reality, as can be seen from the service rating both the front and rear tires are Y rated. The number (e.g., 96 is 1565 lb.) is the load rating while the letter is the speed rating. Speed ratings use to end at V (149 mph). Then they added W and Y (168 and 186 mph) as speed capability went up. The presence of the parentheses around the service rating indicates that the tire has been tested in excess of the speed rating. Thus (99Y) means the tire has been tested in excess of 186 mph. How much in excess??? Only the manufacturer knows that. Bottom line - the presence or absence of Z in the tire size doesn't change the tire size.

JFJr, I think run-flats in the correct size (and service rating) for the 2009 CTS-V will be available in the next year. This assumes that the current economic situation doesn't clobber the sale of the car. Again assuming you are correct and the BMW M5 uses the same size tire, then the total sales might be enough to warrant development of run-flats in any case. I hope so.

edsuski
01-28-09, 01:27 AM
Adding weight near the end of a rotating moment arm is a very bad idea for a performance vehicle. The significant increase in rotation inertia resulting from run-flat tires will reduce the acceleration (thus increase 0-60 times) and increase stopping distances.

The stiffer side walls "might" help with cornering - but the reduced acceleration and increase in breaking distance would more than off-set any advantage gained from stiffer side walls.

If my 2009 V had them - I would sell them in a minute to get rid of them.

tedcmiller
01-28-09, 02:31 PM
edsuski, perhaps you have some test data to back up your claim that run-flats add significantly to the rotating inetia and braking distance. Until I see such data I am not inclined to view a switch from non-run-flats to run-flats as a problem. I still like run-flats. I have a 2009CTS-V. Do you?

The Tony Show
01-28-09, 03:03 PM
When I replaced the stock runflats on my CTS-V I was shocked at how light the wheel was once I took off the tire- I'd bet the wheel literally weighs less than 40% of the wheel/tire combo. I should have thought to weigh the GS-D3s before I put them on, but I'd hazard a guess that they're no less than 5lbs lighter EACH than the F1s.

gotapex
01-28-09, 05:28 PM
edsuski, perhaps you have some test data to back up your claim that run-flats add significantly to the rotating inetia and braking distance. Until I see such data I am not inclined to view a switch from non-run-flats to run-flats as a problem. I still like run-flats. I have a 2009CTS-V. Do you?

For what it's worth, the 285/35R19 Michelin Pilot Sport PS2 ZP (the run flat) is 4 lbs heavier than the standard model, at 32 lbs vs 28 lbs. That is a reasonably significant amount of weight given its location. On the track, 16 lbs (4 tires) worth of unsprung, rotating mass is substantial. It definitely would have made an impact at the Nurburgring.

On the flip side, on the road, and given the overall mass of the vehicle, I doubt most will be able to feel the difference, regardless of how calibrated their butt is.

The Tony Show
01-28-09, 05:38 PM
:yeah:

Also affects acceleration and stopping distances.

edsuski
01-28-09, 06:23 PM
edsuski, perhaps you have some test data to back up your claim that run-flats add significantly to the rotating inetia and braking distance. Until I see such data I am not inclined to view a switch from non-run-flats to run-flats as a problem. I still like run-flats. I have a 2009CTS-V. Do you?

Tedcmiller,

It is really quite obvious if you recall your high school physics. It is all about the energy required to accelerate or decelerate (stop) a car. Think about what happens when an ice skater spins quickly with his/her arms drawn in against the chest and then simply extends their arms. The energy that had the skater spinning rapidly now only spins the skater at a modest rate. This is exactly what happens when you increase the mass of a wheel. Especially when the mass is furthest out from the center of rotation such as on the sidewall or tread of the tire. It simply takes more energy to spin the wheel/tire assembly up and more energy to slow it down. I'm sorry - but this is not debatable. it is simple physics. A previous poster claimed that the difference in tire mass was 4 Lbs. per tire. 4 pounds in the front seat is much different than 4 pounds at the end of a rotating arm.

Oh, and to answer you other question - I do have a 2009 CTS-V that arrived on December 24th - as well as a degree in engineering.

tedcmiller
01-28-09, 08:17 PM
edsuski, I too have degrees in engineering (two of them) and I did not question the physics of your description. I question the word "significant." I have yet to see an specific data from anyone backing up the claim that switching from non-run-flats to run-flats creates a "significant" problem. So far, all I have seen is opinions.

gotapex is the poster who claimed a four pound difference between the the run-flat (ZP) and non-run-flat 235/35ZR19 Pilot Sport PS2. My question to gotpex is where did you get this information. I ask since there is no ZP version of the tire in question. Even Michelin admits that such a ZP tire does not exist.???????????? Perhaps there is a ZP version in a much lower service grade, but that doesn't count. Since there are no equivalent tires (size and service grade) to the non-run-flats that come on the 2009 CTS-V, a switch to run-flats in the same tire is not possible at this time, so the question is mute. I am done with this discussion.

Luna.
01-28-09, 08:25 PM
Perhaps I missed it, but don't anyone know if there are any stabilic-track issues with changing tires heights, like there were/are in the V1?

edsuski
01-28-09, 09:38 PM
edsuski, I too have degrees in engineering (two of them) and I did not question the physics of your description. I question the word "significant." I have yet to see an specific data from anyone backing up the claim that switching from non-run-flats to run-flats creates a "significant" problem. So far, all I have seen is opinions.

gotapex is the poster who claimed a four pound difference between the the run-flat (ZP) and non-run-flat 235/35ZR19 Pilot Sport PS2. My question to gotpex is where did you get this information. I ask since there is no ZP version of the tire in question. Even Michelin admits that such a ZP tire does not exist.???????????? Perhaps there is a ZP version in a much lower service grade, but that doesn't count. Since there are no equivalent tires (size and service grade) to the non-run-flats that come on the 2009 CTS-V, a switch to run-flats in the same tire is not possible at this time, so the question is mute. I am done with this discussion.

Tedcmiller,

Since you are an engineer - this link may help you to understand more quantitatively what the results of adding x amount of weight to a wheel/tire are.

http://hondaswap.com/general-tech-articles/unsprung-weight-part-2-a-29058/

"A reduction in the weight of the rim/tire assembly of 5lbs x 4 (all around the car) is equivalent to a 200lb weight reduction in vehicle weight (thats worth 0.200 in the 1/4 mile)"


Another link that might help:

http://www.xcceleration.com/wheel.chart.htm


"Note: The use of light-weight alloys in wheels reduces rotational mass. This means that less energy will be required to accelerate the wheel. Given that each pound of rotational mass lost provides an equivalent performance gain as a 10 pound reduction in vehicle weight, the benefits of light alloy wheels on vehicle performance cannot be overlooked."

JFJr
01-28-09, 09:58 PM
Sorry, guys. When I started this thread I did not intend to rekindle a debate about run-flat vs. non-run-flat tires. We all have opinions and are basing them on past or present technology. What I didn't understand is why the GM performance division did not have Michelin develop the ZP tires specifically for the 2009 CTS-V (which has been called a 4-door ZR1) before production began. (Michelin did develop such tires for the Corvette ZR1 and all of us have read about its astounding performance.) There are several possible explanations for this (cost, technology (due to a much heavier car, etc.)). I am not an engineer, but one thing I know for sure is that run-flat tire technology could be quite different 12 months from now and that all of us that drive the 2009 CTS-V and later models will be the beneficiaries, assuming that our economy recovers and we are not forced by Congress to drive sorry electric cars.

SRT8/BMW
01-28-09, 10:55 PM
Sorry, guys. When I started this thread I did not intend to rekindle a debate about run-flat vs. non-run-flat tires. We all have opinions and are basing them on past or present technology. What I didn't understand is why the GM performance division did not have Michelin develop the ZP tires specifically for the 2009 CTS-V (which has been called a 4-door ZR1) before production began. (Michelin did develop such tires for the Corvette ZR1 and all of us have read about its astounding performance.) There are several possible explanations for this (cost, technology (due to a much heavier car, etc.)). I am not an engineer, but one thing I know for sure is that run-flat tire technology could be quite different 12 months from now and that all of us that drive the 2009 CTS-V and later models will be the beneficiaries, assuming that our economy recovers and we are not forced by Congress to drive sorry electric cars.

well--I have to cast my vote--or opinion. I am thankful my 09 V has the PS2s and not runflats. I had runflats on my sts-v, Pirellis, and HATED them. They were only good in perfect condtions..(temp, completely dry). On my tuned 335Xi--I t came with all season run flats (Bridgestones). I like them for winter--they are terrific..but in summer I take them off and run non runflats.

At Monticello-the temps were mid to upper 30s and the track was wet--and these PS2s were amazing!! I haven't experienced anything that good in runflats--when pushing a car a little. just my two cents...

RapidRob
01-28-09, 11:30 PM
RapidRoger, the tires I describe are the ones that are on my 2009 CTS-V. The numbers are directly from the side of the tire wall, not from some advertising brochure or magazine article. The presence of the Z in the tire size simply indicates that the tire is rated for speeds in excess of 149 mph. The Z designation came about when tires were developed that could go 150 mph or faster. In reality, as can be seen from the service rating both the front and rear tires are Y rated. The number (e.g., 96 is 1565 lb.) is the load rating while the letter is the speed rating. Speed ratings use to end at V (149 mph). Then they added W and Y (168 and 186 mph) as speed capability went up. The presence of the parentheses around the service rating indicates that the tire has been tested in excess of the speed rating. Thus (99Y) means the tire has been tested in excess of 186 mph. How much in excess??? Only the manufacturer knows that. Bottom line - the presence or absence of Z in the tire size doesn't change the tire size.


Thanks ... good to know, but both the web site and V2 brochure show the non-ZR OEM tires. They must have made a change to which tires are OEM, along with going with the non-slotted rotors and non-metallic front grille.

Rob

gotapex
01-29-09, 02:56 AM
gotapex is the poster who claimed a four pound difference between the the run-flat (ZP) and non-run-flat 235/35ZR19 Pilot Sport PS2. My question to gotpex is where did you get this information. I ask since there is no ZP version of the tire in question. Even Michelin admits that such a ZP tire does not exist.???????????? Perhaps there is a ZP version in a much lower service grade, but that doesn't count. Since there are no equivalent tires (size and service grade) to the non-run-flats that come on the 2009 CTS-V, a switch to run-flats in the same tire is not possible at this time, so the question is mute. I am done with this discussion.

tedcmiller:

I got this info from Tire Rack. They actually measure the tire weights as they get them in, so it's not just a guestimate.

http://www.tirerack.com/tires/Spec.jsp?make=Michelin&model=Pilot+Sport+PS2+ZP&tirePageLocQty=

As you can see the ZP version does exist and in the proper service grade (285/35R19 99Y, for 1709 lbs max load), and it weighs 32 lbs.

The non-runflat version in 285/35R19 99Y weighs 28 lbs:

http://www.tirerack.com/tires/Spec.jsp?make=Michelin&model=Pilot+Sport+PS2&tirePageLocQty=

It doesn't exist in the front size, 255/40R19. Michelin does not make a matching front & rear for this application in the PS2 ZP. They do make the rear application, as I stated above.

jperaino
01-30-09, 12:07 AM
I ordered my CTS-V on Jan. 10, 2009. The dealer gave me a copy of the GM order. It states that my car is coming with Y rated run-flats. I guess I will have to wait and see.

gto_in_nc
01-30-09, 11:24 AM
Rotational kinetic energy (the amount of energy needed just to spin the wheels up to speed) is directly proportional to the moment of inertia. The moment of inertia is directly proportional to the mass of the rotating object (if the geometry stays the same) so this means the change in rotational kinetic energy is directly proportional to the change in mass. Another significant relationship is the direct proportionality between moment of inertia and acceleration, given a fixed torque & moment of inertia. From a little searching, it appears that the stock wheels and stock tires are pretty darn close to equal weights. Without getting into the whole question of "what is the moment of inertia?" (which has already been pointed out to be theoretically simple but practically difficult to calculate but is extremely easy to measure), it is reasonable to say that an increase in tire weight from 28 to 32 pounds is roughly a 1/14th (a little more than 7%) increase in rotating mass. The increase is geometrically distributed in a non-uniform manner, meaning that the inertial constant will actually increase rather than remain constant, meaning that my estimate for the increased energy will be low -- the performance impact will be greater than my ballpark estimate suggests. Anyhow...

A 7% increase in rotating mass (all else being equal) results in a 7% increase in the energy required to spin the wheels up to speed (what speed? Doesn't matter, as long as both cases reach the same terminal angular velocity.) Similarly, a 7% increase in rotating mass also results in a 7% decrease in angular acceleration with a given torque or, to put it another way, it's is functionally equivalent (from a performance standpoint but worse from a drivetrain load standpoint) to a 7% reduction in RWTQ.

So, I'll leave it to the reader to decide what reduction in rear-wheel torque delivered rises to the level of "significant"...

edsuski
02-02-09, 12:07 PM
Rotational kinetic energy (the amount of energy needed just to spin the wheels up to speed) is directly proportional to the moment of inertia. The moment of inertia is directly proportional to the mass of the rotating object (if the geometry stays the same) so this means the change in rotational kinetic energy is directly proportional to the change in mass. Another significant relationship is the direct proportionality between moment of inertia and acceleration, given a fixed torque & moment of inertia. From a little searching, it appears that the stock wheels and stock tires are pretty darn close to equal weights. Without getting into the whole question of "what is the moment of inertia?" (which has already been pointed out to be theoretically simple but practically difficult to calculate but is extremely easy to measure), it is reasonable to say that an increase in tire weight from 28 to 32 pounds is roughly a 1/14th (a little more than 7%) increase in rotating mass. The increase is geometrically distributed in a non-uniform manner, meaning that the inertial constant will actually increase rather than remain constant, meaning that my estimate for the increased energy will be low -- the performance impact will be greater than my ballpark estimate suggests. Anyhow...

A 7% increase in rotating mass (all else being equal) results in a 7% increase in the energy required to spin the wheels up to speed (what speed? Doesn't matter, as long as both cases reach the same terminal angular velocity.) Similarly, a 7% increase in rotating mass also results in a 7% decrease in angular acceleration with a given torque or, to put it another way, it's is functionally equivalent (from a performance standpoint but worse from a drivetrain load standpoint) to a 7% reduction in RWTQ.

So, I'll leave it to the reader to decide what reduction in rear-wheel torque delivered rises to the level of "significant"...

gto in nc,

You are correct in what you are saying and in the way you suggest that your estimate will be on the low side due to some simplification. As you know, the moment of inertia for a solid cylinder is I=1/2MR^2 and for a hoop I=MR^2. Since "most" of the weight of a wheel/tire system is located near the end of the moment arm one could assume that we are dealing with more of a hoop than a solid cylinder and the I=MR^2 formula is closer to what we will see. My point is that the moment of inertia is a function of the square of the distance of the mass from the point of rotation. Adding mass near the end of the moment arm would be much worse (squared rather than linear) than simply distributing the weight evenly over the entire wheel/tire system. As you stated - 7% is a very low estimate and may actually be over 10%. I guess the only question is - how much slower does a proposed changes have to make a car to be "significant". Personally, I'm not spending my money to make my car slower. I don’t know about you but, I have not had a flat that required a tire change (i.e. fast leak) for well over ten years and besides, that “On-Star” button works really well.

JEM
02-02-09, 01:23 PM
I don’t know about you but, I have not had a flat that required a tire change (i.e. fast leak) for well over ten years and besides, that “On-Star” button works really well.

I did have a flat that required a tire change in the M5, the valve stem failed (broke off.) Of course, that car has no spare, it's got the M Blow Me System. The fix-a-flat just oozed right out the broken stem. "Hello, AAA..."

That said, my experience with runflats has been such that I'm not interested in them at their current state of development. The handling deficit is one thing, but they destroy the ride.


http://www.youtube.com/watch?v=35qPZh76AiY

gto_in_nc
02-02-09, 09:51 PM
Hilarious video!

Just for fun, I plugged in a few numbers (and I encourage someone to repeat the process and check my work.) Assuming weights of 28 & 32 for non- & run-flat, respectively, and addressing the differential as a hoop (which slightly overstates the real difference but which is much closer than treating it as a solid cylinder (plus I didn't feel like doing the extra arithmetic to handle it as a thin shell)), along with a few other assumptions (such as falsely assuming the tire doesn't lose effective radius due to bulge from weight of car, etc., etc.), I came up with the following:

The moment of inertia for the non-run-flat is roughly 1.47 while that for the run-flat is 1.68, an increase of 14%.

The rotational kinetic energy of the non-run-flat at 60 mph is about 4550 joules, or 3360 ft-lbs, while that for the run-flat is 5190 j, or 3830 ft-lbs.

At 0-60 in 3.9s, the n-r-f (tired of typing it...) consumes 1.57 hp while the r-f consumes 1.78 hp, a difference of 0.21 hp or 13%.

At 0-120 in 12.3s, the n-r-f eats 1.98 hp while the r-f eats 2.27 hp, a difference of 0.29 hp or 15%.

Putting this all together, it looks like swapping on some run-flats all around has an effect on acceleration that is very close to the equivalent of a reduction of about 1 rwhp.


Frankly, I doubt anyone's noticing this effect very much...

gotapex
02-03-09, 12:55 AM
Frankly, I doubt anyone's noticing this effect very much...

I agree, noticing the effect of the additional weight of run flats on simply straight line acceleration while holding traction constant & without the use of measuring equipment would be difficult.

JFJr
12-23-09, 01:23 PM
For those of you that are interested in Michelin Pilot Sport run-flat (ZP) tires when the time comes to replace the worn OEM tires, here is the latest response I received from Michelin customer service a few days ago: We are sorry but there are no plans at this time to produce the Michelin Pilot Sport PS2 in a ZP version for your Cadillac fronts. Your concerns have been forwarded to the marketing department. I have e-mailed them twice and reminded them that they developed these same run-flat tires for the Corvette ZR1 (a lower production car than the CTS-V), and suggested that there would probably be a market for the ZP's to fit the current CTS-V if they offered them. More e-mails to Michelin from those of you similarly interested might turn their heads.

GMX322V S/C
12-23-09, 01:59 PM
Bridgestone lists our fitment on their master list for their 3rd-gen Pole Position run-flats, but when I inquired about pricing and availability, they shut me down after I told them they would be for an '09 CTS-V. They said it was against company policy to equip run-flats to non-OEM equipped cars. When I cited compatible load ratings, etc, they reminded me there are other factors to consider, such as TC override during a loss of pressure condition, etc. :shrug:

JFJr
12-23-09, 02:14 PM
Bridgestone lists our fitment on their master list for their 3rd-gen Pole Position run-flats, but when I inquired about pricing and availability, they shut me down after I told them they would be for an '09 CTS-V. They said it was against company policy to equip run-flats to non-OEM equipped cars. When I cited compatible load ratings, etc, they reminded me there are other factors to consider, such as TC override during a loss of pressure condition, etc. :shrug:Thanks. Maybe some of the GM engineers that monitor this forum can chime in and advise us if we would have these kind of problems or any other unexpected consequences.

chopmeat
12-23-09, 09:26 PM
I just had a post on Thanksgiving Day, where I pulled out the V to go to family and my front driver's side tire was completely flat with a big nail in it!
I didn"t even realize they were NOT runflats!
That day sucked and I didn't have a flat in probably 15 years...

Caroutisine
12-23-09, 09:38 PM
The fact the V2 does not come with runflats was a positive in my decision to buy the car. That and the auto. I would never put the runflat tires that available today on this car.

Z06ified
12-24-09, 11:13 AM
I agree - I'm glad it doesn't have run flats. I think I'm going to buy one of those professional tire plug kits from my local auto parts store, and keep it in the trunk with the air compressor. I think I have a better chance of fixing a hole in the tire with that than the latex goop they give you. One of my friends said he has used these plug kits to repair a tire on the road several times, and it worked great. I've seen gas station mechanics use them on hole repairs several times, and it looks pretty easy.

This way, the only time you would need a tow is if the sidewall got a tear, the valve stem failed, or some other catastrophic destruction of the tire.

chopmeat
12-24-09, 11:22 AM
Z06ified...
That's what I did, I just plugged it myself and the next day I had them patch it.
I'll evenually get new tires anyway.
But I keep that kit with me in the trunk!

Jpjr
12-24-09, 12:17 PM
I have plugged a goodyear EMT runflat before on my old V1

I hate runflats

Terrible tread wear and unbelievably expensive.

Buy yourselves a $100 AAA membership and enjoy the hour of inconvenience when your tire goes down versus the thousands you will spend every few years replacing runcraps.

Vrocks
12-24-09, 12:28 PM
I was glad to see non-runflat PS2s as the stock tire on the V2. I've had runflats and I didn't like them on my C5 or V1. They don't grip as well, were noisy, and were a pain in the ass to get on and off the wheels.

JFJr
12-24-09, 03:40 PM
All of you who are expressing your negative opinions about run-flat tires are missing the point. We should have a choice; those who want run-flat tires should be able to buy ones of equal or better quality than the OEM PS2's, those that don't like run-flat tires don't have to buy them. There are many good reasons for run-flat tires and technology never stands still. Just remember the current Corvette ZR1 and the OEM PS2 ZP's it wears.

MERRY CHRISTMAS to all and be safe in your ultimate high performance sport sedans (CTS-V's of course)!

JFJr
01-30-10, 01:15 PM
I had the Bridgestone Pole Position RFT (run-flat) tires installed yesterday, and will post my street driving impressions after a few hundred miles. My initial impression is that turn-in is sharper, but having more tread could be a factor.

tedcmiller
01-31-10, 11:20 AM
I did not see these Bridgestone numbers on this thread (I probably put them on a different thread), but these run-flat tires do match the specs for the Michelin non-run-flat PS2s currently provided on the CTS-V. They are Bidgestone RE050A Pole Position/PP RFTs numbers 122018 for the front and 122001 for the rear. They are currently not available through Tire Rack. They will have to be ordered through a distributor and there might or might not be problems with Bridgestone if the distributor asks what kind of car they are for. I would avoid mentioning this to the distributor if at all possible.

JFJr apparently has obtained and installed these tires sucessfully. I will look forward to his report.

In a previous post he mentions that choice is the issue. I submit that in a few years we will have no choice. Run-flats will be mandated by the Feds for all cars (especially if Obama has his way).

Fubar75207
01-31-10, 11:31 AM
It's cheaper to buy On-star for 5 years than the extra $$$ you'll spend on one set of run flats.

neuronbob
01-31-10, 12:13 PM
Interested in JFJr's report as well. Having already gone through a flat tire and lacking both a spare and a tow eye, this is something I could consider in the future as choice is always good. In the meantime, I am planning to re-up on OnStar for three years when the time comes in March as my recent experience using it was positive other than that I spent two hours at the side of the road.

And that is correct, we do NOT have a tow eye/hook in our cars. Don't know what dim bulb decided that basic towing implements were not necessary in this car, but what a terrible idea.

tedcmiller
01-31-10, 09:58 PM
All of the justifications for not using run-flats are valid up to a point. However, with run-flats you can keep on driving. Any other solution, regardless of the money saved, requires that you stop and wait and/or take other action which might be dangerous or extremely inconvenient (changing tires, using goo, or waiting for OnStar or other help to arrive).

JFJr
02-08-10, 12:37 PM
I have put a few hundred miles on my Bridgestone Pole Position RFT (run-flat) tires and will give you my "seat of the pants" evaluation. I won't track my car, so my observations are based on the intended use of these high performance street tires. Bear in mind that I am comparing them to my stock PS2's which had approximately 19,500 miles when I replaced them, so some of the differences could be attributable to that factor. I have set cold pressure at 33 psi for all corners. None of my driving was done at temperatures below 45 degrees.

The Bridgestones's have better "turn-in" than the PS2's and are equally if not more responsive in turns. They are also quieter (no squealing or howling) and as comfortable as the PS2's in normal driving. At times when they are cold after sitting overnight, they may cause a small amount of vibration until they warm up, but when backing out of my driveway with a full-locked wheel turn, going over the curbing at the end of the driveway, the abrupt "bump" or "thunk" I experienced with the PS2's is gone. I have driven the Bridgestones's in the rain and the traction is good, but I have not gone through large puddles to evaluate hydroplaning. I have not pulled a lot of g-forces in turns to check their ultimate grip, but would expect them to handle that quite well. The Bridgestones' wear rating is 280 vs. 220 for the PS2's, so I would expect the Bridgestones's to last more than 20,000 miles before replacement. As an aside my dealer told me that a number of the wheels did not need any weights to balance them after the Bridgestones's were mounted (all are perfectly balanced). I've never experienced that and attribute it to good quality control in both the tire and wheel manufacturing processes. All in all I'm quite pleased with the Bridgestones's and would recommend them to any of you that want run-flat tires on your "V."

neuronbob
02-08-10, 01:31 PM
Cool, thanks for keeping us posted.

JFJr
10-20-10, 10:33 PM
So Ed Piatek, speaking of old threads, what can you tell us regarding run-flat tires for our cars? I will need new tires in about 15,000 miles and am running (I hope) Bridgestone run-flats at the present time.

Jud

tedcmiller
10-20-10, 11:16 PM
The Bridgestone PNs that were run-flats are no longer run-flats. They are conventional tires. I checked the Bridgestone listings and sent an e-mail to Bridgestone when I could no longer find those PNs listed as run-flats. Bridgestone confirmed that those PNs are no longer run-flats and are now conventional tires. There are some MOE tires for the Mercedes that are the correct size for the CTS-V but do not mention the CTS-V if ordering from Tire Rack as they will not ship tires that have not been tested on the car that they will be put on. JFJr came in under the wire and put the previous Bridgestone PNs that were run-flats on his car just before they changed them.

Eslocklier
10-20-10, 11:19 PM
I guess I can see the benefit in them for safety purposes, but in a car marketed on being sporty it only makes sense to have the best handling tires available come as standard issue.

tedcmiller
10-20-10, 11:30 PM
I like run-flats because of the convenience, which leads to safety. I like the sporty aspect of the CTS-V, but I want convenience too.

Tuna
10-25-10, 01:04 PM
Last month before I sold my V1, my wife cut the sidewall in the left front tire (1.5 in slice right out of it) while driving in a construction zone on a turnpike. She called me on the phone to tell me about while driving on to her destination about 15 miles away. Without the run flat tire, she would have been stuck on the side of the turnpike waiting for me or someone else to come get her and fix the tire. I'll take run-flats any day over non-run-flats especially if the car does not come with a spare or jack or lug wrench.

Btw, the run-flats that were on my V1 were GY F1 GS D3 in 255/45/18 and I loved them. Great mileage and great traction - all year.

I will be watching for run-flat production in the V2 sizes and will probably change out to them when they become available.

New Bee In New York
10-25-10, 06:15 PM
If only there was a reasonably priced donut that would fit in the well. The performance of the PS2's and the ability to change a flat ... what an idea!!!

Z06ified
10-25-10, 06:37 PM
If only there was a reasonably priced donut that would fit in the well. The performance of the PS2's and the ability to change a flat ... what an idea!!!

The wheel well and price of the donut isn't so much of an issue as finding a spare wheel that would clear the huge brake calipers, and fit both the front and back wheels.

New Bee In New York
10-25-10, 06:43 PM
The wheel well and price of the donut isn't so much of an issue as finding a spare wheel that would clear the huge brake calipers, and fit both the front and back wheels.

Sorry, I thought my post didn't need to state the obvious.

tedcmiller
10-25-10, 09:22 PM
Those people who want a spare tire are missing the whole point of run-flats. With run-flats you keep driving. Without run-flats you have to stop. Whether or not you do anything while stopped is your choice. But, you still have to stop.

New Bee In New York
10-26-10, 12:35 AM
For the appreciable improvement in traction, cornering, etc., I'll change a tire. I have no issues with anyone else using run-flats on their car. I think I'll stick with what Cadillac thought was best.

tedcmiller
10-26-10, 02:53 PM
OK. For an improvement in traction etc. ("appreciable" is an opinion without any facts to back it up) you would prefer to stop in the rain/snow/dark/unlevel ground (or maybe all four) and take the time to do whatever is required. Each to his own.

New Bee In New York
10-26-10, 08:44 PM
OK. For an improvement in traction etc. ("appreciable" is an opinion without any facts to back it up) you would prefer to stop in the rain/snow/dark/unlevel ground (or maybe all four) and take the time to do whatever is required. Each to his own.

I say run flats give you a hasher ride, don't corner as well and don't ride as well in the rain. To answer your question, YES, I prefer to run non-run flats and I'll chance the rain/snow/dark/Ooooo, scary/unlevel ground and take the time to do whatever is required. I have PS2's on my Z06 too. Obviously no spare there and I've driven it cross country twice ... AND WITHOUT RUN FLATS ... Wow, am I brave or what!!! On my cross country jaunts I made sure to carry a scissor jack and plug kit along with the OEM inflater.

Tell the truth now ... you own an appreciable amount of stock in a run flat manufacturing company, don't you?:histeric: :histeric:

Nine Ball
10-27-10, 11:07 AM
This thread is quite comical to read. Especially when guys list all their previous cars, and that someone must own a CTS-V to provide their own commentary or opinion on tires.

Well, I've owned numerous high performance cars. Around 10 of them at the moment. Yes, I own a 2009 CTS-V too. Z06, Viper, etc... Most of them came with run-flat tires. I can't stand those tires on a performance car. The Michelins on the Viper were by far the worst, traction-wise. The ones on the Z06 actually weren't that bad. I carry a can of fix-a-flat and a plug kit for road trips, because I prefer having traction. I also do track my cars, and the run-flat tires are garbage there too. Need a factory example? The 2008+ Vipers switched from run flats to conventional Michelin tires once the power went up to 600 hp.

I agree that the run-flats are better for daily commuting, due to convenience and safety. No question here. I'd expect that for a commuter car, something I drive like Miss Daisy in. Not for something with 500+ hp though. I'll take the scary awful terrible risk of having a flat, in trade for having traction every day.

Tony

New Bee In New York
10-27-10, 12:13 PM
:2thumbs: Well said!

tedcmiller
10-27-10, 11:33 PM
Sorry, I own no stock at all - in a run-flat manufacturer or any other kind of company. This thread has become very boring. I don't plan to look at any more.

New Bee In New York
10-28-10, 01:04 AM
Sorry, I own no stock at all - in a run-flat manufacturer or any other kind of company. This thread has become very boring. I don't plan to look at any more.

I'm sure you'll be missed.

bob_go
12-31-10, 04:16 PM
Michelin now offers runflats for the 2009 CTS-V, rear tires only (Pilot Sport AS+ ZP). As they do not offer the runflats for the front tires, will there be any issues with mixing non runflats (Pilot Sport AS+) with the rear runflat tires?

I'm also contremplating the Continental Extreme Contact DW tires. Has anyone had experience with this brand?

Silver -V-
12-31-10, 06:40 PM
I have been running the Michellin set up for a year now. No issues, as far as tires go. The grip isn't nearly as good, but better than most tires, and they have a 30k mi. warranty. The tires won't grip as much, but you won't get only 7500 miles out of them like I did with the stock PS2's.

I keep a second set of tires on wheels for the road course, and am very happy with the 2 set set-up.

chicaboom
01-01-11, 04:37 PM
What does the new CTS-V Sedan come with now from factory runflat or non runflat?

Tuna
01-02-11, 03:04 PM
Goodyear has an F1 GS-D3 RoF (run-flat) tire in 285/35/19 but they do not have the D3 run-flat for the front. GY does have a 245/40/19 D3 run-flat but going slightly smaller probably isn't the answer.

I hope my OEM PS2s last a little longer than the GY Supercar tires my V1 came with. When the PS2s are gone, I'll be looking for a run-flat and hope GY makes the D3 in the right sizes by then.
Maybe Michelin will make the new PSS in the right size and run-flat also.

In the meantime, I spent the money on the spare tire kit from Eurotek Designs - I don't want to be caught out with a flat tire and no spare.

chicaboom
01-04-11, 03:19 AM
Goodyear has an F1 GS-D3 RoF (run-flat) tire in 285/35/19 but they do not have the D3 run-flat for the front. GY does have a 245/40/19 D3 run-flat but going slightly smaller probably isn't the answer.

I hope my OEM PS2s last a little longer than the GY Supercar tires my V1 came with. When the PS2s are gone, I'll be looking for a run-flat and hope GY makes the D3 in the right sizes by then.
Maybe Michelin will make the new PSS in the right size and run-flat also.

In the meantime, I spent the money on the spare tire kit from Eurotek Designs - I don't want to be caught out with a flat tire and no spare.

Do you mean it comes with runflats in the front tires and nonrunflats in the rears? That doesn't make sense?:bonkers:

neuronbob
01-04-11, 06:52 AM
No. The car comes with neither run- flats nor spare tire.

No manufacturers offer a complete set of aftermarket run-flats in stock size. One vendor makes an expensive spare tire kit for our cars.

chicaboom
01-04-11, 07:11 AM
No. The car comes with neither run- flats nor spare tire.

No manufacturers offer a complete set of aftermarket run-flats in stock size. One vendor makes an expensive spare tire kit for our cars.

I thought it was a 200 dollar option to get a spare tire unless that's for the 6 cyclinder model?
So then if you have a CTS-V what do you do? Get a compressor and plug kit like they used to supply on the old C-5 Corvette Z-06?

mik2718
01-04-11, 08:07 AM
Yes, the factory optional spare does not fit the CTS-V. Instead, the CTS-V comes with a "tire inflation kit" (compressor plus goop).

Tuna
01-04-11, 09:59 AM
Do you mean it comes with runflats in the front tires and nonrunflats in the rears? That doesn't make sense?:bonkers:

No. I wrote that GY makes a run-flat in the "REAR" tire size but not one for the front.
So far, I have not found a single tire type that has run-flats in both the stock sizes for the V2. Michelin is coming out with the new Pilot Super Sport tire this year in both run-flat and regular tires. Maybe they will make the run-flat (or ZP) version in the V2 sizes. Maybe GY will make the F1 D3 EMT/RoF in 255/40/19 this year.

When I find a suitable set of run-flats for my V2, and the OEM tires are close to worn out, I'll put run-flats on the V2. In the meantime, I bought the Eurotek Designs spare tire kit - I don't like the idea of being stuck out on the road with a flat. Last year, my wife cut the side wall out of one of the GY F1 D3 EMT tires I had on my V1 and she kept on driving it for about 20 more miles. If it had been a regular tire, she'd have been sitting on the side of the road in a construction zone waiting for a tow as the V1 didn't have a spare either.

JFJr
05-16-11, 12:35 PM
Matt Reiland, or any other GM executive monitoring this forum, can you give us any clues as to when run-flat tires will be available in the proper sizes and load rating for the 2009+ CTS-V sedan? Some of us don't track our cars and appreciate the obvious convenience and safety of run-flats. My Bridgestone Pole Position RFT's are wearing out and I will need replacements this year. Thanks.

Jud

chicaboom
05-16-11, 01:46 PM
Runflats won't provide any more performance to the car in fact it may diminish performance perhaps that's why there is no spare.

JimmyH
05-16-11, 02:29 PM
runflats are horrible. kudos to GM for getting rid of them.

I think the spare tire will soon be extinct from all cars. All GM cars come with onstar now don't they? That's what they are pushing.

JFJr
05-16-11, 02:48 PM
Thanks to all of you for your opinions on run-flat tires; there are dozens of them in this thread, pro and con. The good news is that no one is required to buy them, if they don't want to. The flaky inflator kit or OnStar are no help to me with a flat on a business trip, wearing a suit on a hot day, when I'm on a time schedule. Give me a break guys, I'm just trying to get some information from GM.

Jud

JimmyH
05-16-11, 05:15 PM
You were required to buy them on the first gen CTS-V. The single greatest mod I ever did to that car was get rid of the run-flats. Both ride and handling improved significantly. As did mileage. The first gen spare well in the trunk was able to swallow a full size spare though.

If you are set on a spare, search this forum. someone determined that the regular CTS spare will fit with some modifications. I think a spacer was required and some machining to the rim. The 2nd gen CTS spare is a cast rim, not a stamped steel wheel.

dznr723
05-16-11, 09:33 PM
Was reading this thread with a great deal of interest. Last week i had a catastrophic blowout on the front tire of my V coupe when i must have hit a pothole.The hole in the sidewall was at least 3 fingers wide. So you can imagine my surprise when i opened the trunk and realized there is no spare tire in the V coupe.
Called the Cadillac "hotline" and the gentleman suggested i use the inflator kit.It may as well have been a chrome plated paperweight for all it was worth at that point. So then he said they would send a tow/flatbed truck to pick my car up and deliver it to the closest dealer.By the way this happened on a Sunday evening @8PM,so there was no way anything would be open at that time.
1 1/2 hours later a flatbed truck finally shows up ,and the driver takes one look at the car and informs me that the car will not be able to go up the ramp of the truck because with a flat tire,the already low front end will never clear the ramp.Not the right answer says i.He had several 2X4's,so we made a makeshift ramp and i drove the car gingerly up the "ramp" while the driver guided me.
Needless to say,i was not a happy camper.The dealer didn't charge for the tow,and the insurance covered the tire cost ($500) !!Just never anticipated this kind of tire failure and then discovering the lack of a spare.
End of rant. :)

JimmyH
05-16-11, 09:52 PM
that's the other thing; a run-flat can blow out. I know it's highly unlikely. But then :knockonwood: I have had one flat in 20 years. And that was on stupid-ass 35 series tires I had on my car for three minutes.

chicaboom
05-16-11, 11:38 PM
Re: Why No Run-flat Tires?
that's the other thing; a run-flat can blow out. I know it's highly unlikely. But then :knockonwood: I have had one flat in 20 years. And that was on stupid-ass 35 series tires I had on my car for three minutes.




Well if you do have a blow out with a run flat won't you have a better of control whereas on a regular tire one is more opt to loose controL?:bomb:

chicaboom
05-16-11, 11:39 PM
You were required to buy them on the first gen CTS-V. The single greatest mod I ever did to that car was get rid of the run-flats. Both ride and handling improved significantly. As did mileage. The first gen spare well in the trunk was able to swallow a full size spare though.

If you are set on a spare, search this forum. someone determined that the regular CTS spare will fit with some modifications. I think a spacer was required and some machining to the rim. The 2nd gen CTS spare is a cast rim, not a stamped steel wheel.

Alot of Corvette owners are switching to non runflats with success.

chicaboom
05-16-11, 11:42 PM
Was reading this thread with a great deal of interest. Last week i had a catastrophic blowout on the front tire of my V coupe when i must have hit a pothole.The hole in the sidewall was at least 3 fingers wide. So you can imagine my surprise when i opened the trunk and realized there is no spare tire in the V coupe.
Called the Cadillac "hotline" and the gentleman suggested i use the inflator kit.It may as well have been a chrome plated paperweight for all it was worth at that point. So then he said they would send a tow/flatbed truck to pick my car up and deliver it to the closest dealer.By the way this happened on a Sunday evening @8PM,so there was no way anything would be open at that time.
1 1/2 hours later a flatbed truck finally shows up ,and the driver takes one look at the car and informs me that the car will not be able to go up the ramp of the truck because with a flat tire,the already low front end will never clear the ramp.Not the right answer says i.He had several 2X4's,so we made a makeshift ramp and i drove the car gingerly up the "ramp" while the driver guided me.
Needless to say,i was not a happy camper.The dealer didn't charge for the tow,and the insurance covered the tire cost ($500) !!Just never anticipated this kind of tire failure and then discovering the lack of a spare.
End of rant. :)

Isn't this called the "Cadillac Tax"?

JimmyH
05-17-11, 12:28 AM
Re: Why No Run-flat Tires?
that's the other thing; a run-flat can blow out. I know it's highly unlikely. But then :knockonwood: I have had one flat in 20 years. And that was on stupid-ass 35 series tires I had on my car for three minutes.




Well if you do have a blow out with a run flat won't you have a better of control whereas on a regular tire one is more opt to loose controL?:bomb:

I have no idea. I have never had a blowout. I don't know how run-flats shred compared to regular sidewalls.