View Full Version : Alternate Optimal Tire Sizes

08-25-06, 06:37 PM
I just picked up my new CTS-V and am planning to replace the tires with a little meatier selection. Through research on this site it looks like stocks up front and 275/40-18's in back on the stock rim will work well. Another option that I'm considering however is 265/40-18's all the way around. Tire height is -.17", and weidth is +.78" as compared to the stock 245/45-18. Has anyone tried this size? How's it look? Any issues? I appreciate any comments.

08-25-06, 06:45 PM
I'v got Falken Azenis RT615 255/40/18 all around. awsome tire. If your going with non runflat, i recomend those or michelin PS2. They are closest comparison to F1's.

08-25-06, 06:48 PM
Here's a V with 265/40/18 Michelin Pilot Sport 2 tires all the way around...

eBay Motors: Cadillac : CTS (item 270020718234 end time Aug-31-06 06:45:00 PDT) (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=270020718234&ih=017&sspagename=STRK%3AMEWA%3AIT)

Been thinking about 265/35s for my next set.

08-25-06, 09:16 PM
What are you looking to accomplish with the wider tires?

08-25-06, 10:48 PM
I primarily want to give it a tougher look. A little wider tire out back might come in handy from time to time as well. Every car I buy, I usually go a size or two larger.

08-26-06, 12:07 AM
I think 255 is the max recommended width on the stock 8.5" rims. Beyond that and you could be pushing the margin of safety. And yes, you may find some on this forum who have gone wider than 265 on the rear on stock rims. The info I'm quoting is from tire manufacturer and seller sites. Please go look and judge for yourself. On the front, 265 is the max regardless what you decide on the rim width. I think I read somewhere here 9.5” is max rim width for the rear with 10” cutting it a little to close to suspension pieces.

Look closely at the eBay picture. That car has not been lowered and the gap with 40 series tires is significant. (The angle of the photo helps minimize it.) Also, the outer edge of the tire is right at the fender line. There will be rubbing if the car is later lowered. This car will probably be fine with the driver only and normal road conditions. A full passenger load or conditions that bottom-out the suspension will likely cause rubbing.

These tire/size threads usually get a lot of attention. I’m mentally prepared to be judged out of my skull for the above statements, but those who do so judge, please also leave behind you real-world experience. My real experience is 265/40/18 on 9” wide rims rub front and back after the car was lowered 1” in front and .75” in back. I’m having flares done to take care of the rubbing and I’ll post pictures soon as I get it back.

09-02-06, 04:58 PM
im running 275's on the rear with no propblems.

09-02-06, 09:51 PM
Here's my real world experience.

275/40's in the rear on stock rims and about .5" lowered with absolutely no rubbing issues whatsoever (sub and amp in the trunk, two kids in the rear, and maggie pulling me through the turns).

275's on widened stock rims (same tires as above - GSD3's) with a rim width of 9.25" using .2" spacers and again, zero tire rubbing issues EXCEPT for an incident when the jergoff alignment technician didn't finish his job and the tire found the fender as I pulled out of the lot. Easy fix for the alignment - not so easy for the fender (minor rolling back to factory shape required - inside fender lip only). This applies for stock ride height down to about 1" lower in the rear.

275/40's on 9.5" stock rims (widened) with same .2" spacers, Bridgestone RE050A's, and there are issues. Ideally, the best fix would be .3" spacers but then I should change to longer wheel studs. Minor rubbing at 8/10th's and above (.85g sustained or so) of the wheel against the lower trailing rod. Also minor rubbing (but it sounds absurd) of the tire against the faintest little bulge on the inside fender sheet metal. Should grind it off - but I won't - since I've checked it out and know it is just a noise that occurs and nothing bad is happening (very corner of the tread block comes into contact). Again, I'm about .75 to 1" below stock ride height.

Now for the front. I've never run anything except 245/45's and I can tell you that if you lower the V at all - you WILL have issues with wider tires. They might be minimal like my slight rubbing in the rear mentioned above (no, it isn't CVP). They might be more significant and cause fender lip damage in a parking lot type maneuver turning while transition through a dip or over a speed bump or pinecone or?

Now, we've seen and heard that 265/40's can work all the way around with close to stock ride height. Even Mallett mentioned to me that you can get away with wider tires and wheels if you jump to 19's in the front (I forget the details) UNLESS you lower the car drastically (like anything over .25"). I'm lowered about 1" in the front and when I was more than that - rubbing during turns and sweepers was the norm.

Real world experience requested and delivered. One final note for you. So far with the RE050A's, while plush with good turn in and quiet, I haven't seen above .91g on the meter. Maybe I'm just slowing down. Maybe they "talk" more and slow me down before their limits. And maybe, just maybe, the F1's in originial size are superior.


09-02-06, 10:03 PM
Oh yeah, almost forgot.

275/40/18's on stock rim, stock width, won't even bolt onto the front without hitting the upper A-arm pinch bolt. Don't even try it.


09-02-06, 11:34 PM
I'm just curios why you widened the wheels if the 275/40's worked well on the stock rims....

09-02-06, 11:56 PM
Ummm, I never said they worked well on stock rims, I just said they fit. While they were OK, I believe they are better on wider rims. Sidewall is more square, not bulged out. Personal preference I suppose. I think I reported before that the expense of widening the wheels likely isn't worth it in this case.

Of course, they are an inch wider now. Seems life is always about measurements :stirpot:



09-03-06, 12:10 AM
Oh yeah, almost forgot.

275/40/18's on stock rim, stock width, won't even bolt onto the front without hitting the upper A-arm perch. Don't even try it.

Thanks, this just saved me from making a mistake. You 'da man..

09-03-06, 02:31 AM
I currently run 255/40/18 Falken RT-615 all around on stock rims. No rubbing eventhough I'm lower by .875" front and .625" rear on Ground Control kit. I've just recently noticed Falken makes the same RT-615 in a closer fitment to the stock size. It's a 255/45/18.

09-04-06, 02:34 AM
Here's 265/40/18 BFG KD's on 9x18 Jongbloed rims, all four corners... but the flares will cost ya!

09-04-06, 02:48 PM
I'm just curios why you widened the wheels if the 275/40's worked well on the stock rims....

Ever seen a tire sidewall jump right off the rim due to too much lateral force? Its not pretty.

Nuff said.

09-04-06, 02:54 PM
Ever seen a tire sidewall jump right off the rim due to too much lateral force? Its not pretty.

Nuff said.