: Michelin tire question



VA Maddog
07-24-07, 11:13 AM
I recently bought a used 05 STS AWD and it came with a nearly new set of Michelin's. The tires are Pilot HX MXM4 Zero Pressure Radial XSE M+S (97W) and are all the same size, front and back P235/50 ZR 18.

I have a few questions.

The first question is - What impact does it have that they did not put the wider tire on the rear wheels? The car handels wonderfully and tracks true, so I sure can't notice any issue, but what do I know. Looking for more of an expert opinion here. They must have speced the rear tires as being slightly larger for a reason.

Second question; I have read some posts about how certain Michelin tires are very noisey. These tires are in fact very noisey, a lot noisier than I would expect. At slow or moderate speeds the tire noise on the pavement is very obvious, expecially in a car that is otherwise so quiet. My thought is that it is in fact the tires causing this as the noise level changes with the type of road surface. It gets much quieter on a newly paved road or on a concrete surface. While the allignment might be off a little I can tell you that the car tracks perfectly on the HWY and I notice absolutely no pulling or any other indication of a problem.

So the bottom line is - am I just stuck with a set of almost new very noisey tires? What success has anyone had in working with the local Michelin rep on this issue? Is the front/rear size difference anything to worry about?

Thanks in advance for your thoughts!

Caroutisine
07-24-07, 08:40 PM
Don't know about the noise issue, but I replaced mine with the same size tires on the factory rims front/rear with no issues. I used the OEM front tire size for all 4.

z06bigbird
07-25-07, 12:33 AM
We are all curious of the Michelin rep helps you. Maybe copies of various threads talking about noise levels of Michelins would help. Keep us posted.

VA Maddog
07-25-07, 08:28 AM
I am probably at a disadvantage since I did not purchase the tires, they came with the car, but I do plan to try working with my local tire shop GM who I have a good relationship with to see what he suggests and to see if there is merit in trying to engage the regional Michelin rep in a conversation about the problem.

It really surprises me that Cadillac stuck with this particular tire as an OEM tire with the noise issue. All of the other reports I read about the tire are pretty favorable, the noise seems to be everyones biggest complaint.

I'm curious - are many others here on this board experiencing the same tire noise issue with this tire?

thiamgo
07-26-07, 04:03 PM
Just save your time and buy Kumhos for a third of the price of Michelins. I was forced to buy new tires at 10K mls because of an irrepairable puncture. Read several reviews and decided to buy Kumho at Tire Rack. Better traction and car is silent since. BTW in every review the Mich's come out as noisy. You can talk till hell freezes over with any rep but it's looks just a (bad) characteristic of the product. Just like the unsatisfactory traction.

Jesda
07-26-07, 05:15 PM
Kumhos start out very nicely but dont wear quite as well as Michelin or Bridgestone. I'll second the noise issue with Michelins.

Spend some time on Tire Rack and go through the surveys.

sts/allante
07-28-07, 10:34 PM
My 2006 STS awd with the 1SC package came with Michelin Energy LX4 tires in 235/50 R17 with a 95S rating on all 4 rims. I believe this tire was std for the AWD cars in place of the Pilot HX MXM4 V rated tires that were on the RWD cars.

Heavy_Metal
07-29-07, 07:25 PM
VA Maddog, I also have a 2005 1SG AWD and replaced all four tires with Michelin Pilot Sport A/S 255/45. I have had no trouble with them being all the same size. Also the tread life, wet traction, and dry handling of the Michelin Pilot Sport A/S seems to be better than the original equipment tires.

Force-1
07-29-07, 11:59 PM
VA Maddog, I also have a 2005 1SG AWD and replaced all four tires with Michelin Pilot Sport A/S 255/45. I have had no trouble with them being all the same size. Also the tread life, wet traction, and dry handling of the Michelin Pilot Sport A/S seems to be better than the original equipment tires.

The Pilot Sport A/S are great tires. I ran them on a Lincoln LS V8 Sport, which came stock with the HX MXM4 tires too--Pilot Sport A/S much better. I got almost 30k miles out of them before the center bar wore down too much.

VA Maddog
07-30-07, 08:27 PM
Force-1 and Heavy Metal - Did you notice a big difference in tire noise when you went to the new tires? Were your old tires very noisy on normal surfaces and even worse if the asphalt was older and rougher?

Force-1
07-30-07, 10:03 PM
Force-1 and Heavy Metal - Did you notice a big difference in tire noise when you went to the new tires? Were your old tires very noisy on normal surfaces and even worse if the asphalt was older and rougher?

I didn't notice much noise change going from Michelin to Michelin on my LS.

I recently got rid of the HX MXM4s on my STS and replaced them with Kumho's. The Kumho's are quieter, track better, and handle better than the OEM Michelin's IMO.

Heavy_Metal
08-02-07, 05:31 AM
Force-1 and Heavy Metal - Did you notice a big difference in tire noise when you went to the new tires? Were your old tires very noisy on normal surfaces and even worse if the asphalt was older and rougher?

It seems like the Pilot Sport A/S tires make more noise than the HX MXM4 tires and I agree that the sound changes a lot with road surface for both tires. I think the ride is also a bit more stiff with the Pilot Sport A/S tires. Even so, the STS is still a very quiet, smooth riding car. Personally, I like the Pilot Sport A/S tires much better due to the improved performance especially on wet roads.

VaDoug
08-31-09, 06:23 PM
I have a 2008 STS with a set of Pilot HX MXM4 tires that howl and ride rough. When first starting off in the mornings the car rides like all 4 tires have flat spots. I have taken it to one Michelin dealer and he told me it was my car. I am taking it to another dealer tomorrow to see if they can find out what is wrong. I am beginig to think after reading the posts, this is a design problem. Why doesn't GM or better yet Michelin recall these crappy tires? I have never owned a Ford let alone a Caddy that had tires this bad. Where is Caddilac on this issue?

SleeprLegend
08-31-09, 06:40 PM
The Michelin rep can do nothing for you. They are one of my grandfather's customers. The size difference can make a difference since all gearing, speed, odometer, etc are based on the circumference of the rear tires. Those numbers don't just mean wider tires. Tires that are too narrow for a rim will receive increased ware and decreased traction over the proper tires. This only applies if you have a different width rim front to rear.

You can't get the new Michelin Pilot Sports for the OEM 17's, but those are my favorite. Here are the options for the OEM 17's:
Tirerack.com - 2005 STS v6 OEM tire size matching front and rear (http://www.tirerack.com/tires/TireSearchResults.jsp?tireIndex=0&autoMake=Cadillac&autoYear=2005&autoModel=STS+V6&autoModClar=Standard+Model&frontWidth=235/&frontRatio=50&frontDiameter=17&frontSortCode=49890&rearWidth=255/&rearRatio=45&rearDiameter=17&rearSortCode=50200&tab=All)

ChrisHall
09-01-09, 09:08 AM
How to calculate rim plus tire diameter:

Front tire on a 2008 STS AWD
P235 50R18
235/25.4*.50*2+18=27.25"Diameter

Rear Tire on a 2008 STS AWD
P255 45R18
255/25.4*.45*2+18=27.03" Diameter

The front tire rotates 740 times in a mile and the back tire rotates 746. This is nothing on your speedometer.

These tires are close enough that you can put either or on front or back. Your speedometer won't notice the 1/4" diameter difference.

For winter I plan on buying 17"x8" rims with a 43mm offset and a back spacing of 6.22". Winter tires I will be using are the Michelin Pilot PA3 P235 55R17.

P235 55R17
235/25.4*.55*2+17=27.18" Diameter

This diameter falls right in between the front and back tires and rim diameter and will work perfectly on the front and back.

Hope this helps.

Back to the original question:
I also have the Pilot HX MXM4 tires on my car. They will definitely not be going back onto my car when they're done. First thing I noticed was the road noise when I drove my car.

Cheers,
Chris

Force-1
09-01-09, 09:19 AM
I just noted that the OP has run flats on his vehicle. Were run flats OEM for the AWD STS? Run flats are known to be noisier than regular tires.

SleeprLegend
09-01-09, 04:11 PM
How to calculate rim plus tire diameter:

Front tire on a 2008 STS AWD
P235 50R18
235/25.4*.50*2+18=27.25"Diameter

Rear Tire on a 2008 STS AWD
P255 45R18
255/25.4*.45*2+18=27.03" Diameter

The front tire rotates 740 times in a mile and the back tire rotates 746. This is nothing on your speedometer.

These tires are close enough that you can put either or on front or back. Your speedometer won't notice the 1/4" diameter difference.

For winter I plan on buying 17"x8" rims with a 43mm offset and a back spacing of 6.22". Winter tires I will be using are the Michelin Pilot PA3 P235 55R17.

P235 55R17
235/25.4*.55*2+17=27.18" Diameter

This diameter falls right in between the front and back tires and rim diameter and will work perfectly on the front and back.

Hope this helps.

Back to the original question:
I also have the Pilot HX MXM4 tires on my car. They will definitely not be going back onto my car when they're done. First thing I noticed was the road noise when I drove my car.

Cheers,
Chris

Tirerack.com shows 255/45-18 as the OEM performance tire/wheel option, the only 18", for the 2008 STS V8 AWD on both front and rear. I usually pick a tire that I want and then find the right rims to get everything to work on the specific car.

To answer your original question. I recommend Michelin Pilot Sport A/S Plus (http://www.tirerack.com/tires/tires.jsp?tireMake=Michelin&tireModel=Pilot+Sport+A%2FS+Plus) tires. I just noticed than have a run-flat version if you need that.

Added: The circumfrance is the number that effects the gearing. You need one more step to nail the difference between the tires.

EChas3
09-01-09, 10:02 PM
Run flats usually require special rims that won't accept standard tires. (As costly as $400 per tire.) Don't want 'em, wouldn't have 'em. Just me - no offense intended.

My 2006 AWD with OEM staggered 18's came used with the 235's on the rear and the 255's on the front. It freaked out the salesman that had to comp the swap. It caused no trouble at all.

It's an open differential and isn't off enough to affect any of the other systems. That said, I'll be going with 255's all around when they get replaced.

ChrisHall
09-01-09, 10:55 PM
Re:Added: The circumference is the number that effects the gearing. You need one more step to nail the difference between the tires.

I believe I did start talking about the circumference. I just didn't finish it.

"The front tire rotates 740 times in a mile and the back tire rotates 746. This is nothing on your speedometer."

This means after 1 mile, the front tire rotates 6 times less than the rear. After 60 miles, it rotates 360 times less. That's about 1/2 a mile difference after 60 miles. This means that if the larger tires are on the rear, car will be going 60 mph and spedometer will show 60mph. If the smaller tires are on the frear, car will be going 60 mph and the spedometer will show 60.5 mph.

You are correct that my car came stock with the 18 inch rims, but it is difficult to find a package that isn't too expensive. (Not Cadillac rims for snow and salt)This package works for me and the tires stated have a very good review.

Cheers,
Chris.

Onalaska
09-01-09, 11:31 PM
After driving my STS for about three years I really think the road noise is more a function of the design of the car rather than the brand of the tire. There is just not that much isolation from the road in the STS. In Texas they use a road surface known as chip and seal and the car is real noisy on this type of surface regardless of the tires. My Chevy Silverado is a lot quiter than the STS on this type of surface. So is my Fleetwood Brougham and my Allante. It's not just the type of tire, it's the design of the car.

EChas3
09-02-09, 11:05 AM
After driving my STS for about three years I really think the road noise is more a function of the design of the car rather than the brand of the tire. There is just not that much isolation from the road in the STS. In Texas they use a road surface known as chip and seal and the car is real noisy on this type of surface regardless of the tires. My Chevy Silverado is a lot quiter than the STS on this type of surface. So is my Fleetwood Brougham and my Allante. It's not just the type of tire, it's the design of the car.

That makes sense. It's an engineering tightrope to design a car with sport road sense while dampening poor road conditions. But surely the tires can make a big difference.

PS: Did you know you have a town named after you in Wisconsin? Onalaska is just north of La Crosse on our western border (The Mississippi River).

next2pool
09-02-09, 01:24 PM
After driving my STS for about three years I really think the road noise is more a function of the design of the car rather than the brand of the tire. There is just not that much isolation from the road in the STS. In Texas they use a road surface known as chip and seal and the car is real noisy on this type of surface regardless of the tires. My Chevy Silverado is a lot quiter than the STS on this type of surface. So is my Fleetwood Brougham and my Allante. It's not just the type of tire, it's the design of the car.


Tires are part of it, but as you say the basic design and tuning of the car are a major contributor. As a former ride & handling guy, road noise was always something we worked hard on. Full frame vehicles were much easier to quiet down. Unibody vehicles (even those with sub-frames) are much more difficult. Then you get the ride vs handing tradeoffs as well as acoustic damping vs weight tradeoffs. My personal opinion is that the STS has way too much road noise. BTW, we use chip seal roads extensively for noise reduction work.

SleeprLegend
09-03-09, 02:04 AM
After driving my STS for about three years I really think the road noise is more a function of the design of the car rather than the brand of the tire. There is just not that much isolation from the road in the STS. In Texas they use a road surface known as chip and seal and the car is real noisy on this type of surface regardless of the tires. My Chevy Silverado is a lot quiter than the STS on this type of surface. So is my Fleetwood Brougham and my Allante. It's not just the type of tire, it's the design of the car.

I'm not so sure about the road noise being due to lacking of sound insulation. If you just take a door panel off you will see how far Cadillac went to quiet down the interior of that car. One thing to remember is that a larger diameter wheel means you have a lower profile tire. That lower profile tire has less "suspension", for lack of a better term, ability which results in increased road feel. It also increases your cornering G between matching 17" and 18" tires. It also increases road noise, and usually contact patch since 18" are usually wider. All this adds up to a problem on anything but the smoothest surfaces.

Greg00coupe
09-03-09, 02:07 PM
I'd agree runflats are nosier........been there done that with a Corvette. However I have 2 sets of wheels and in buying the second set never was told you need special wheeks for runflats. Never heard of that but maybe it's true.

Force-1
09-03-09, 08:17 PM
I'd agree runflats are nosier........been there done that with a Corvette. However I have 2 sets of wheels and in buying the second set never was told you need special wheeks for runflats. Never heard of that but maybe it's true.

Not true on a Corvette. They come from the factory with run flats; however, many owners replace them with non-run flats, mounted on the OEM wheels.

SleeprLegend
09-04-09, 05:25 AM
Not true on a Corvette. They come from the factory with run flats; however, many owners replace them with non-run flats, mounted on the OEM wheels.

My convertible Vette has the run flats. The world sucks when one gets a leak, but I can't talk and fit the rules of this forum.