: HELP: Has anyone mounted larger tires on stock rims?



jmos77
12-11-09, 05:08 PM
Has anyone mounted larger tires thatn the stock 285's on the stock 19" rims? I jut went to mount my winter tires and they are 295 35 19 and the installer said they wouldn't fit. i cant imagine how this is possible and I thought I saw others mount larger tires than this on the stock rims. Any feedback would be greatly appreciated. Thank you

cbloveday
12-11-09, 09:28 PM
I find it odd that you are mounting larger winter tires? Most people mount OEM size. Did you question the installer further as to why they would not fit?

Luna.
12-11-09, 10:20 PM
Can someone please refresh my memory of what the stock width of the front and rear rims is please?

neuronbob
12-11-09, 11:10 PM
Width is 9" front, 9.5" rear, 51 mm offset front, 56 mm offset rear.

Stock tire size is
255/40-19
285/35-19

Luna.
12-11-09, 11:23 PM
Width is 9" front, 9.5" rear, 51 mm offset front, 56 mm offset rear.

Stock tire size is
255/40-19
285/35-19

Well, this is where I'll hate GM again... :rant2:

They put 255s on 9" on the front, which makes really good sense, then, INEXPLICABLY, put 285s on 9.5" rims in the rear?

For the love of God, someone please help me understand this bullsh*t, for I'm very confused.

The recommended rim width for a 285 is 9.5" to 11", which means that it appears GM put the SMALLEST recommended rim for a 285 tire.

295s, however, have a recommended min. rim width of 10", so this isn't a combination that looks very appealing to me. Yeah, you CAN do it, but I've gone down that road on my V1 & I don't want to do that again (I put 275s --RUNFLATS--on the stock 8.5" rims and that was AWFUL, as the tire simply rolled over the rim...was a disgusting, unsettled feeling...with 10" rims on the rears, the 275s are monsters again, but I digress...)

Note that this doesn't even bring to light that a 295/35 is closer in tire height to the 255/40, than the 285/35 is (as mentioned in the previous thread), so now I'm really just shaking my head...

Will a 10" rim fit on our cars? I really wanted to go 295s when I have to change tires, but I'm not dealing with a tire that doesn't "fit" on the rim again...

ericpd
12-12-09, 12:35 AM
Jeez,... I just received my 295/35's from UPS today with an appointment for install tomorrow morning. Please tell me (link) where got the rim/tire size recommendations from. I just started a thread on this yesterday. http://www.cadillacforums.com/forums/cadillac-cts-v-series-forum-2009/186973-buying-tires-tire-rack-com.html

Wished I had read your post before I pounded on the submit button on Tire Rack's checkout page.

jmos77
12-12-09, 01:19 AM
Well I originally bought the tires for my M3 and I figured going from 285 tp 295 would not be a problem. To my surprise the installer says they are "way too big". I thing they are full of crap ecause I didn't buy the original tires tfromthem aso back to my orginial question is will they fit? Has anyone mounted alrger than the stock size 285's on their stock 19" rims? Thanks

Luna.
12-12-09, 02:10 AM
Jeez,... I just received my 295/35's from UPS today with an appointment for install tomorrow morning. Please tell me (link) where got the rim/tire size recommendations from. I just started a thread on this yesterday. http://www.cadillacforums.com/forums/cadillac-cts-v-series-forum-2009/186973-buying-tires-tire-rack-com.html

Wished I had read your post before I pounded on the submit button on Tire Rack's checkout page.

LOL--I think it was from Tire Rack's website a few years ago! :D

I widened my rims on my V1, as I was running an overboosted maggie and 255s weren't enough rubber in my mind. As such, I did a lot of research about how to work a solution and ended up widening the tires to 10" (which is about the max you can go with the V1 and even then I had it mini-tubbed to handle that) to fit a 295. Why? Because the tire height worked near-perfect with 255s in the front--same combination I'm looking to work here.

As far as WHERE that's at, well, hopefully I can find it again. I'm sure it's out there though...

EDIT: Here you go: http://www.tirerack.com/tires/Spec.jsp?make=Michelin&model=Pilot+Sport+PS2&partnum=93YR9SPORTPS2XL&partnum=73YR9SPORTPS2XL&vehicleSearch=false&fromCompare1=yes&place=7

Note that this is NOT the end-all, be-all of facts in life, but it definitely is something to at least consider. Personally, for me, I utterly loathed it in my V1, so much so that I'm not willing to take that chance on my V2, BUT others like it just fine, so keep that in mind.

AZstar
12-12-09, 08:43 AM
I don't have any first hand experience with wider tires on the back of the '09 V, but I would be surprised if those tires don't fit on the rims or if they don't fit in the wheel well. I think the more important question that seems to remain unanswered is whether the 1% increase in circumference will cause problems with the traction control. If you do mount them, please report back any traction control problems.

As far as information about the appropriate rim width for your tires, go to the tire manufacturer's web site. It should tell you the recommended widths.

musclesbmf
12-12-09, 08:44 AM
go to a different installer...
the 295 will fit just fine.

Mark

AZstar
12-12-09, 08:49 AM
Well, this is where I'll hate GM again... :rant2:

They put 255s on 9" on the front, which makes really good sense, then, INEXPLICABLY, put 285s on 9.5" rims in the rear?

For the love of God, someone please help me understand this bullsh*t, for I'm very confused.

The recommended rim width for a 285 is 9.5" to 11", which means that it appears GM put the SMALLEST recommended rim for a 285 tire.


I fail to see why that should make you angry. Since the majority of people who own these cars will not install wider tires, GM did us a favor by not putting heavier, more expensive wheels on the car that most of us don't need.

From my experience at the track, the car already understeers, the last thing I want is wider tires in the rear. If I could fit wider tires up front, I might consider it.

ericpd
12-12-09, 09:15 AM
Great point AZ,... never thought of about it from that angle. I think what Luna was saying was the up front they designed in some flexibility, however out back, they choose to max us out the moments our boots hit the LZ. Most OEM wheels come with enough headroom to bump 1,... if I understand what's being said, our rear wheels have the headroom designed out of them.

I will find out in a few, I'm leaving for my scheduled for an install as soon as I finish this taza de café y rosquilla de cebolla. I'll report back anything of interest or value. My installer is the local Firestone shop near me. Now I'm wondering if they don't fit, will they do an exchange for the proper size? I wonder how deep their relationship with Tire Rack actually is? Think I'll try and find that out before I leave,.... What happens if the tire sizes are incorrect or if there's any other problem? Are these 'Preferred Installers' empowered to help with a resolution?

Damn,... you guys got me scared now. Damn ya'll! LOL!

neuronbob
12-12-09, 11:01 AM
Please tell me (link) where got the rim/tire size recommendations from.

This information, other than the offsets, can be easily found on many car-related publications on the web that have reviewed the CTS-V. The information has been amply confirmed here over the last year. Oddly enough, it's not listed on any GM web sites. In any case, an Edmunds link is as good as any:

http://www.insideline.com/cadillac/cts-v/2009/full-test-2009-cadillac-cts-v.html

The offset information comes from Dr. Design at D3, who posted this info on this forum.

HTH! Do let us know whether the wider tires work out.

ericpd
12-12-09, 05:20 PM
This information, other than the offsets, can be easily found on many car-related publications on the web that have reviewed the CTS-V. The information has been amply confirmed here over the last year. Oddly enough, it's not listed on any GM web sites. In any case, an Edmunds link is as good as any:

http://www.insideline.com/cadillac/cts-v/2009/full-test-2009-cadillac-cts-v.html

The offset information comes from Dr. Design at D3, who posted this info on this forum.

HTH! Do let us know whether the wider tires work out.

Just getting back in. the 295's went on without an issue. Didn't do Firestone, ended up going to a nearby NTB shop instead,... nothing to do with installation, all logistics. The guys at NTB assured me that a one size bump in our case carried little to no risk and that my V was not the first to their shop seeking the same treatment. I specifically asked about the wheel width issue, and he showed me another chart showing that our rear wheels were within a range compatible for 295's. I also learned that the taller the tire, the more flexibility you have with sizing up,... that our wheels could accomodate 60 series tires up to 305. I guess this explains why I've seen some posts in here talking about 305 drag radials on our wheels. If I'm not mistaken, they're pretty tall tires.

Something else,... NTB does price matching. This includes Tire Rack. So theoretically I could have saved 60 or so bucks ($31.50 shipping + $30.75 installation) had I just purchased the tires from them. Sales tax is a wash, as Tire Rack also charges Sales Tax. Interesting.

So,... now I have Hankooks on the back and PS2's up front. Weird! The ride feels no different than before so far. Only done about 12 miles on them, so I guess I have some more driving to do before I can really speak to their impact on the car.

Thanks guys,... and thanks for the thread Luna!

jmos77
12-12-09, 08:20 PM
Thanks for the update. Can you let me know the exact size of the 295's you mounted? Thanks

ericpd
12-12-09, 08:55 PM
Thanks for the update. Can you let me know the exact size of the 295's you mounted? Thanks

295/35 19! Take note,... some members are saying Caddy fitted our V's with the minimum wheel width 9.5" capable of handling the 285's issued with the car, leaving no headroom for a size bump to 295's. There are several charts that plot tire size and wheel width matchups (check out the two links in this thread). One says 9 and a half inches ain't enough to accomodate a 295 with a 35 wall,... however, I've seen two that say 9.5 makes it by the skin of it's teeth. NTB had a similar chart stating that 9.5 is sufficient.

If you do Tire Rack, their site may show 295/30 19 for this Hankook. It is actually a 295/35,... which is a good thing because most of the guys in here who know this stuff, say that that tire's circumference is not tall enough for our cars. I'm guessing it would have the V standing like a hyena,... tall legs up front and short thick legs out back. Plus, like I said earlier, a 295 with a 30 wall definitely won't fit our 9.5 wheels.

The exact impact of having/wheel mix-match (wheel too narrow) I don't know. But from reading in here, it's not hard to guess it ain't good.

musclesbmf
12-12-09, 11:23 PM
you need a need a 295 35, which is only slghtly larger diameter than stock 285 35. 295 30's are too short and would look stupid with stock front tires.

Mark

Luna.
12-13-09, 03:17 PM
I think the more important question that seems to remain unanswered is whether the 1% increase in circumference will cause problems with the traction control. If you do mount them, please report back any traction control problems.



Unless the system tracks rotations of the exact 285 tire, which doesn't make much sense, there would probably be LESS issues with Stabilitrac with the 295 combination I discuss before in this thread. The tire heights are actually closer with the 295 than the 285.




I fail to see why that should make you angry. Since the majority of people who own these cars will not install wider tires, GM did us a favor by not putting heavier, more expensive wheels on the car that most of us don't need.

From my experience at the track, the car already understeers, the last thing I want is wider tires in the rear. If I could fit wider tires up front, I might consider it.

No, they DIDN'T do us a favor by not putting, "heavier, more expensive wheels on the car that most of us don't need."

Yeah, like any of us NEED 556hp stock...like any of us NEED to spend $60K+ on a high-performance 4-door sedan, like any of us NEED to modify these cars... Give me a break...:cookoo:

And the majority of people wouldn't change the rear tires if they came stock with 295s either, so please stop the propaganda that 285s are what the majority of people want. Many, if not most, simply aren't going to change the stock rims/tires due to a whole host of reasons, like cost, trust in GM engineering, looks, etc.

Now, IF there was a VERY good reason, say, "We wanted to install a 10" rim for the rear tires, but we opted against it because the tighter sway bar in the rear (to help cause oversteer) didn't offset the increase in weight at the rear corners. Etc." then I COULD understand that.

HOWEVER...

I do NOT believe that to be the case. I see this as a similar situation to the utterly egregious decision to install CAST pistons in the LSA motor, rather than forged pistons, like in the LS9. For what I gather from people who specifically dealt with GM on this exact issue, it came down to a VERY dubious cost decision; one that doesn't make much sense. Would the total number of CTS-V sales significantly decrease with a, say, $200 increase in the total cost of the car? Ummm...that doesn't strike me as reasonable.

And it's fairly easy to help offset increased wider tires in the rear; we did it a lot on the V1, say, like installing a tighter sway bar...BigJim is one that comes to mind when he installed 275s on his V1 and I believe he very much liked the Hotchkiss Sway Bar and 275s pretty well. I'll let him discuss that more though, as he understands it better than I do, but that's what I seem to recall.

I have an idea...

Why not simply have GM put a 300hp motor in the CTS-V and go with 225s all the way around? They could install much smaller rims, which would save cost, as well as weight, and most wouldn't change them... :annoyed:

ericpd
12-13-09, 05:13 PM
Someone please explain how wider tires in the rear encourages understeer? I keep hearing that in many of the posts here and can't quite get my mechanical juices around that concept. Thanks. I've gone through life think that the wider the footprint the better the grip, the better the grip the better the control and agility.

GMX322V S/C
12-13-09, 06:56 PM
^^ In a turn, with more grip in the rear, the fronts will break traction and push to the outside of the turn before the rears. Ways to compensate include a stiffer rear stabilizer bar, stiffer rear dampening, less front dampening, or...wider front tires...

Fastlane 09 CTS-V
12-13-09, 10:33 PM
I have 325/30-19's on the rear of my 2009. They do fit without mods, but don't recommend it for the street. I did it to drag race... I drive them on the street, but the rear end is very loose.

ericpd
12-13-09, 11:28 PM
^^ In a turn, with more grip in the rear, the fronts will break traction and push to the outside of the turn before the rears. Ways to compensate include a stiffer rear stabilizer bar, stiffer rear dampening, less front dampening, or...wider front tires...

Ooooooh,... I think I understand. Loosen up the rear to correct the front and visa versa. A grippy ass won't allow the rear to swing around and shift the weight to help steer the front. So it ends up pushing all the weight and momentum directly at the front, pushing it forward no matter what direction the tires are facing. Sorta like trying to steer on a sheet of ice. Brake the rear end loose and you can get a little aided steering from swinging back end around. If this is right, then I got it,... if not, then I'm still confused and hopeless.

Being that our front wheels aren't maxed out like our rears, it shouldn't be a issue bumping up one size up front and regaining the balance.