p3rs1st

Hey guys, the problem I am experiencing in a new to me 2017 991.2 C2S is the car is pulling to the right under any form of acceleration or just coasting. Pulls harder if you accel harder, and of course you correct, then when you let off it wants to dart left so you have to correct the steering wheel again. To clarify further on this, i dont think accelerating harder actually makes it pull harder, you just travel the same distance quicker, if that makes sense. The pull isnt THAT crazy, i mean I know I've had vehicles in the past (SUVs in particular) that slightly go one way or other just due to tire sizes, road variables, etc but in my jeep I dont really care because I'm not trying to drive spiritedly in in a jeep, :P In a 911 this would obviously be a major issue and I definitely wouldnt be doing any kind of event like this, let alone spirited driving on the street.

I had an alignment done, they said the front was off. Did not fix the issue.
Verified PSI in all 4 tires is matching. about 30 PSI all around.

Now after reviewing the tires I have the following observations:
- front tires, PZERO 245's both nearly new, datecode 2020
- rear passenger tire, PZERO 305/30/20 nearly new, datecode 2020
- rear driver tire, PZERO 305/30/20, much less tread than the rear passenger tire, datecode 2019.

I'm hoping this tread level difference/or other reasons are the culprit and I'm looking to see about getting two identical tires to swap out the rears for testing. I just so happen to have some other All-Season PZERO's from a different car that are 305/35 ZR20 107Y and they are brand new. Could I put these on the rear temporarily to see if it fixes the drifting? (I actually started writing this post thinking they were only 275 but after checking the garage i was happy to see they were actually 305's so that shouldn't be a problem at all IMO)

I'm trying to hold out for the new upcoming bridgestone potenza sport tires so I'd probably use these all-seasons until they come in, if the AS's fix the pulling issue.

Thoughts?

Dan

BSO

I'm no tech, but what you describe is a significant pull, which seems to me more than what would be caused by differences in tread depth.

You fail to mention what brand(s) the rear tires are. Are they different makes? You don't mention this but can it be assumed they are the same size?

The pull you describe, is this a force actually moving the steering wheel or are you turning the wheel to correct the pull, as the force causing the pull is coming from the elsewhere.

I would check the suspension throughout the car, bushings, connecting points, sway bars, shocks, the works. Something is out of spec and exerting acceleration makes it worse, so this force is causing something to be pushed/pulled out of spec.

This would alarm me as it could lead to a sudden failure of a component at a bad time.

Hope you get it pinpointed ASAP.

GT3FZS

I had the identical problem with my 2019 Carerra T,
The problem was Pirelli P Zero rear tires were slightly different in diameter due to a 2/32 inch difference in tread depth. The right rear has less tread, and under acceleration/squat the car pulled hard right. I swapped the tires right to left, and then it pulled left.
Replaced the P Zero's with Michelin PS4's, problem solved.
I did do a 4 wheel alignment after the PS4's were mounted, and added a bit of camber front and rear, and the car is perfect.

thesaintusa

Have had this scenario with tires that wore differently, i.e. tread depth.

p3rs1st

thanks for all the input so far. It's a relief to hear similar issues to mine with the swapping of tires resolution. fingers crossed, i should know tomorrow

Hopefully it does the trick and I dont need to get into finding a good shop to look at the suspension components. Only bad thing about being over an hour from a Porsche dealer

BSO

I just replaced one of the front tires in my C4S due to a nail. The other front tire had about 13k miles.

I expected that the difference in tread depth would cause the steering to pull but the car steers and drives just as before, even at WOT.

Hoping that's all it is for you.

BTW, I know they are expensive, but Michelin PS4S tires are pretty much a first choice for many that have posted here, maybe give them some consideration.

gskv

camber and alignment of sports cars being more aggressive tend to get pulled into the ruts on the road.

fnckr

I had this exact issue on a 993 with slightly different air pressures in the rear tires. Once equal, it drove straight. These cars are sensitive to tire differences.

p3rs1st

Quick update: changing the rear tires FIXED the issue, sooo relieved. I wont leave these on for long, just enough to order some new summer tires for all 4 corners. thanks everyone for the input.