Cadillac CTS-V - My V is swerving/floating under hard acceleration

I'll make this as short as possible. Today i ran over a flat piece of metal which probably got kicked up with my front tire and then got ran over with my rear right tire and blowing it out :mad: Both rear tires have less than 2k miles on them. In the rear i'm running Sumitomo HTR Z II 275/40 but now i have a fairly new 245/40 bridgestone that i had stored and now it's replacing the busted Sumitomo. Well under hard acceleration the car feels like it floats from side to side and i have to try hard to keep it straight, is this common with a different sized tire or do i have have something else going on? I ordered a new 275 which will hopefully be in this week. Oh yeah, here's some pics of the piece of metal and tire





https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash3/s720x720/535284_3615118650286_1043424010_3317102_57488739_n .jpg

https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc7/s720x720/389640_3615086209475_1043424010_3317093_1071464640 _n.jpg

did it go all the way through?

did it go all the way through?

Yep, it was barely sticking out of the tire and it was a pain in the ass to pull it out.

I wouldn't think the tire would cause that since its the same overall diameter. I notice my car feels kinda wishy washy in the ass end at times when accelerating but more so when cornering. I posted a thread about this awhile back and no one had an exact answer as to what causes it. I'd bet it has something to do with the cradle bushings in the rear and possibly tailing arms or whatever else is back there that's supposed to keep the car planted but could be gettin worn out.

Did you have it aligned?

Improper toe in (not enough) of the rear can cause it to "walk" or drift under acceleration.

Its not the same overall diameter. A 275 40 18 would put a 26.7 inch diameter... a 245 40 18 would put a 25.7 inch diameter. An inch shorter, which is significant enough to affect handling. If you have a 245 45 18, you'd be where you needed to be in terms of tire diameter.

So yeah, I think an inch shorter tire then the others can affect the handling.

Ahhh... missed that. Thought it was a stock 245 he was running. I didn't see that it was a 245/40.

Ahhh... missed that. Thought it was a stock 245 he was running. I didn't see that it was a 245/40.

LOL Yeah. Stockers would be a perfect match at 245 45 18s.

Did you have it aligned?

Improper toe in (not enough) of the rear can cause it to "walk" or drift under acceleration.

Not yet, as soon as the matching tire comes in i will definitely get it aligned, thanks!

Its not the same overall diameter. A 275 40 18 would put a 26.7 inch diameter... a 245 40 18 would put a 25.7 inch diameter. An inch shorter, which is significant enough to affect handling. If you have a 245 45 18, you'd be where you needed to be in terms of tire diameter.

So yeah, I think an inch shorter tire then the others can affect the handling.

That makes a lot of sense, this weekend i'm going to look at the rear suspension and make sure nothing is messed up just in case.

dayum the tire how did you get a pic of my wife as your avatar...lol

A full inch shorter in diameter and you didn't notice? HELL F'N YEAH that will cause problems. Aside from that, if you have the smaller tire installed as a temporary fix that you aren't 100% sure of, functionality wise, WHY WHY WHY are you accelerating hard? Personally I wouldn't drive the car at all with tires that mis-matched. JMO

Yeah, too much driving with odd heigth tires can burn up your rear.

According to shipping the tire will be here tomorrow, i only got on it once (habit) and when the car shifted i haven't done it since. The tire itself is practically brand new with no issues.

The difference in tire diameter shouldn't affect driving too much... If it did the ABS light would come on. If it was a side to side mismatch I'd be more concerned. If you're alignment is good the instability is most likely from the squishy bushings or perhaps worn bushings

The difference in tire diameter shouldn't affect driving too much... If it did the ABS light would come on. If it was a side to side mismatch I'd be more concerned. If you're alignment is good the instability is most likely from the squishy bushings or perhaps worn bushings


... How wouldn't 1 shorter tire on 1 side affect driving? I would agree if all 4 were an inch shorter, but 1 shorter then the others would definitely affect handling and driving.

... How wouldn't 1 shorter tire on 1 side affect driving? I would agree if all 4 were an inch shorter, but 1 shorter then the others would definitely affect handling and driving.

Well for starters I need to learn how to read because I didn't see the part about the odd tire being put on in place of the rear tire. I thought that it was a difference between both front and rears tires...