K-A

Anyone experienced anything like this? I took my 2012.5 in for the recall (appears to be emissions related and replacing a heat shield) and some new rear tires.

Immediately I noticed something different through especially long sweeper turns after picking it up when driving aggressively. It’s as if my traction control detects slipping when there is none and starts to either pull throttle or auto-brake the car.

Upon further investigation by coasting down fast sweeper turns, I realize it’s in fact clearly braking occurring. Like as I turn the car through these either long or tight sweepers, I can feel it braking most likely one or two wheels to slow down. Almost like an ESC way overreacting but no lights or anything come on.

My car has PTV+ so not sure if related or if by design (or maybe this is how PTV+ works and mine finally just started working? Lol), but it never was intrusive at all before. Since the recall and tires, it started. Can’t say it’s better or worse but it just feels odd as it’s correcting things I don’t need corrected. Maybe it’s an extra safety measure but it actually freaks me out more, for obvious reasons.

Any ideas?

Thanks.

LexVan

How many miles on the tires?

Tire pressures?

Ambiant air temperatures?

I suspect you have not worn off the mold release yet and are getting extra slippage, the PTV and PSM are intervening. Cold weather and over inflated tires will exacerbate the safety devices.

LexVan

How many new tires.....2 or 4? Front or rear??

K-A

Interesting! Didn’t know about mold release.

Just two new rear tires. Same Pirellis as the fronts. The fronts probably have a good at least 50-60% tread left. Current rear pressure is about 42 cold and front pressure is maybe 32-34 cold (they pumped the rears up too much) so around an 8 PSI difference (I usually like it around a 4-6 PSI difference). I was thinking that may be a factor but I’ve had large variables between the front and back before and never experienced this.

It definitely does feel like it’s detecting some slippage and intervening. Most noticeable if I just cruise downhill through some windy turns, not hitting the gas, and feeling it pumping brakes through every curve.

LexVan

OK, you just introduced a ton of oversteer into the car, by way of new, slick (mold release) over inflated rear tires, with nice grippy front tires. Lower the rear tires, and after 500 miles or so they will scrub in, and things should settle down a bit.

LexVan

Also, driving downhill transfers weight to the front tires. You guessed it. Extra grip up front, rear get loose, PTV and PSM kick in. Physics.

K-A

Hah. Makes perfect sense. I’ll lower the rears and break em in more and see how that works. I figure the sudden auto braking can’t be great for brake wear either, but hopefully not too bad at the same time. Thanks again.

2-Rotor

Is your car PDK or 7MT?

K-A

PDK.

991carreradriver

I think you should head off to your shop and have your PASM checked on PIWIS. I have broken in "on track" over 20 sets of new tires and NEVER experienced what you are describing, including overheated and over inflated tires. I have heard of PASM malfunctions that cause what you are describing.

DBH

Agree with LexVan. Drive 200-300 miles to break-in the tires and you should be okay. Be sure you've got tire pressures adjusted to your preferences - full/partial load and comfort/standard pressure.

WP0

Is this a new recall? (Just asking because I haven't gotten a notice or request to bring my 2015 991.1 C2 in for work, but maybe it was done last year)

LexVan

It's NOT a recall.

It was NOT done last year.

Call your dealership tomorrow AM. Have them run your VIN for the two open campaigns. See the other active "Heat Shield" thread for more info.

These are the campaign codes:


WLA4 - Retrofit heat shield
WLC8 - Replacing tank leakage diagnostic module

nstar8

Had the same effect 2 months ago when I only replaced the rears with 305's on m y 2014 /c2s...Had them put the original size new tire on, and problem was still there, just not as bad. I was able to put 200miles on those tires as I was out of town on business trips. My tire research from this board and the tire manufacturer shows you must go through some heat cycles (~500 miles) of normal driving and it has been suggested to drop the rear pressure down to 34 vs. the 43 that they put in. That should solve the problem....

K-A

Awesome, thanks for the replies. I’ll drop the pressure and give it some time and go from there. My car originally came with 19’s but my wheels are now 20’s with 305’s (they’ve been that way since I bought the car).