Traction control taking over around corners

I had new tires installed on the rear yesterday, some Hankook Ventus V12's, and all was good until I decided to accelerate around corners. I would get the traction control flashing light on my dash and feel the brakes kick in. It would pulse on-off-on-off until I was around the corner. Needless to say, I did not have this problem with the old tires . And I doubt the issue is with the tires themselves. What could the installer have damaged either lifting the vehicle or removing/reinstalling the wheels that could explain this?

Looking at exploded part diagrams of the rear axle...are there just speed sensors? Any other pitch/yaw type accelerometers attached to control arms, etc.?

Fresh tires are always slippery....drive a full tank or two. Did you check tire pressures?

+1 - what he said - New tires have a molding release compound on the surface which can make them slippery until you scuff them in a bit. Probably nothing to do with the installation.

Thanks guys! I did check pressure and they were up at 38 each which is where I had my last set. I also just pulled both wheels off for a visual and could not find anything...other than the lug bolts were not very tight. I drive it some more as you suggest and see what happens.

it wasnt active handling psm that lit up ? the tires need to be scuffed up. you did use a torque wrench on the bolts ?

Will commence scuffing immediately. As for torque wrench ...I used one today...installer must not have. Not sure about the question on active handling psm. The orange triangle icon on the instrument display would flash on and off and the car would accelerate and brake and accelerate and brake while I kept the pedal constant. This would only happen when I could get some lateral g's. Hard acceleration on a straight would not cause any issues.

Same here with new rear Michelins that replaced same S2. Tires still shiny so being aggressive on corners is not comfy yet. Looking forward to scuffing them at Driver Skills day this Saturday and then go from there.

If I'm not mistaken the PSM measures slip angles to determine when it needs to activate. My experience has been the deeper the tread, the earlier it activates. With race tires or worn out street tires the threshold is a lot higher.

Man, I hope I do not have to live with this very long. I bought the car a year ago and it already had 18k on the tires ...well seasoned. I've never driven it with new tires before, but this is certainly not the Porsche experience I was used to. Same great car on straights...but worse than my Ford F250 diesel on corners.

It's still acting up?? This is a long shot but maybe whoever installed the new tires knocked a sensor wire loose back there or something. Might be worthwhile to remove the rims and double check everything back there. Maybe someone with more experience at how things are connected back there can chime in. Just came back from a 2000 miles road trip to the Dragon and I think I saw the PSM light up once even on all those curvy roads.

What size of tries are the rears, and what size are the fronts?

Don't you just HATE IT when the wheels fly off at speed! Dave

In the interest of passing along lessons learned, I thought I'd share what finally resolved my issue now that it seems to be fixed. As I stated earlier, I replaced my rear tires only...from PS2's to hankook V12's. I left the front tires alone...PS2's...since they had considerable tread remaining. Every time I took a corner, PSM would kick in and apply brakes. I also noticed that at freeway speeds the car felt so unstable that if any quick maneuver was required I'd flip over. I noticed that if I turned PSM off, the cornering issue fixed itself. But the car still felt very unstable above 40 mph. I was quite concerned that the tire installer bent/damaged my suspension on a lift to cause these symptoms. I found a number of posts where folks said it was ok to run mismatched tires as long as those on the same axle matched...so I should have been OK. But then I came across a post where someone claimed their car was very unstable with mismatched front/rear tires . Running out of ideas, I decided to have matching front tires installed yesterday and am thrilled to report everything is now back to normal. While I've never run mismatched tires before, on any car, it was hard to imagine the difference in tread would cause such an issue...but it did. My car feels like a Porsche again...so relieved. Hopefully my experience will prevent someone else from making the same error. Do not run mismatched tires .

Thank you for the followup. How many miles did the fronts have on them again?

29k miles on the fronts and rears. I bought the car 1 year ago with 18K miles, so the previous driver must have not done much spirited driving. I confirmed via markings on the tires they were original to my 2005. The rears had some time left but were leaking due to a number of screws stuck in one tire. The fronts had screws in them as well but had not lost any air. I was hoping to get another 5k miles but the mismatch prevented that.

OK that was not obvious in your initial post. I had to replace my rear PS2's since my front PS2's still had lots of tread. I had contemplated getting rear Goodyear F1 Asymmetric since they were better value but my installer advised against it. Either get all 4 Goodyear or replace with PS2's. My rear PS2's run fine but now I am thinking maybe I should have bit the bullet and gone all 4 Goodyear instead. Or try to burn through these PS2's as soon as possible...

Anyone got any explanation for why mismatched tyres on front & rear axles could cause PSM to play up?? Whilst I've never done it, I always thought as long as the left and right sides were the same it shouldn't matter. Besides, the front and rear tyres have different widths anyway, and thus slightly different characteristics...... I thought something like this would only matter in an AWD???? (confused)

This is a REALLY good thread. I posted about something similar in the Competition forum. I installed new and taller.wider 275-40-18 tires on the rear but left fronts unchanged - 235-40-18. PSM did not like that, and I basically had to turn it off to get the car to behave. I think the explanation is simple, although just a guess. Our PSM compares front wheels speed to rear wheel speed. Since now the new larger wheel (275 in my instance, and new rubber in yours) turns slower than the fronts PSM assumes that traction was lost in the rear and intervenes. It also could be that although a standard size 265-40-18 or 265-35-19 the V12 tires are just taller. There is quiet a difference in diameter and width between same size tires from different manufacturers. I never believed that it could be so sensitive, but it is on my car, and seems to be on yours. I would say that running Porsche spec tires in the stock sizes is advised unless you want to experiment with PSM. Tomasz

In support of Tomasz's hypothesis, I also went to 275/40/18 rears, but with 245/40/18 fronts (R888 tires ). Thus, both ends were slightly taller than OEM sizes, but the PSM sensors apparently thought that was just fine. Like several others here, I've also gone to 265/35/18 rears (about .8" shorter than OEM) with 235/40/18 fronts in Michelin Cup tires with no complaint from the PSM sensors. I also think it's a good idea to try to keep the front-to-rear mechanical tire grip difference close to what OEM provides. Having different tire brands at each end might not do that very well. This consideration even questions replacing the tires at one end without also replacing the tires at the other end, which are, after all, the same age as the tires being replaced. So far, I've replaced all four each time, but I didn't always do that on my pre-PSM cars.

Almost the exact same issue here. My CS, bought in February with 19K on original tires , needed new rears around 28K. Money's a bit tight, plus my front PS2's were good, one of them only a month old (replaced for road hazard). I also bought the Ventus V12's for my rear and their tread depth is deeper than the original PS2's. Right away, the car feels unstable at speed and turns I took on nearly bald rears at 70 mph were now causing PSM to kick in unless I was around 60 mph. I hate to replace my fronts where one is almost new and the other with seemingly 50% tread left, but it's a bitch to drive this way. I turned off PSM and it feels a little better, but the ABS interrupts anyway. I have a few favorite corners I can slide around to scuff the rears a bit, but after 2 tank fulls, it still doesn't feel right. Is there anyway to reset the PSM or recalibrate it for these new tires ? Otherwise, I may have to bite the bullet and replace my fronts with matching Ventus. Anyone in the San Diego area want cheap, nearly new PS2 fronts?

I'm going to post here instead of starting a new thread. I have a similar issue. In my case, I have 37K mi. and went in for service, brakes and replace the 2 rear tires (with the same size and brand I had before and they match up front). Got new rotors and pads up front and aligned all wheels (had some funny wear on the fronts). Driving home on a big right hand on ramp I feel PSM kicking in. In 4 years I've never felt it unless it was wet. Happened a few days later but worse...really felt it on the left front in the right hand turn. Took the car back in to check for something loose, etc. but like the posts here everything looked ok. So, slick new tires ?? Fronts still have 10K on them so I'd rather not replace but really don't like this feeling. Anybody have any new feedback on this issue? Thanks!

I'm gonna revive this thread. Ditto, Ditto, Ditto to everything said. 1st set of tires was Conti 2 Did not like the asymetric tread pattern or the rim protection bead in the middle of the side wall. Bought a complete set of Hankooks last season. 235/35/zr19 front 275/35/zr19 rear Why? cause I liked the tread pattern and price. There were awesome after about a week of breaking in. For some reason the rears wore out before the fronts. :hilarious: So bought just a pair for the rear. PSM light comes on regularly on winding road driving... and I live off a 17 mile winding mountain road. Turning the PSM off helps some... but the handling still feels loose and rolly during cornering. After reading this entire thread and many others using search on PSM... I am hoping that after I wear down the rears a bit more... shouldn't take too long :hilarious:... that the car will return to it's previous handling characteristics. I'll give it 500 miles... If that doesn't do it... then I guess I'll buy a pair for the front. My guess is that the combination of tire height difference between old and new, and the tire size difference front and rear, and the slickness / softness of new tires is causing the PSM to be activated too often. Do you agree? "Fastang" translated into German is "Cayman S"

I think there may be a number of factors that influence it ultimately, such as wear differences on the tyres front and back, optimum pressures for them and compound types. I'm running PS2's on the rear and Pzeros on the front with no issue, but both sets are well worn in. For those with brand new tyres and having the PSM come in quicker than before, start with checking the pressures and then allow the new tyres to wear in a bit before dumping new fronts on. It is very often worth getting alignment checked as well, especially considering how much we spend on tyres, so you wnat them to last as long as possible. What Tomasz and Jim said runs very true from everything I have seen and because of the balance of the 986/987 is perfect, if you are increasing the rears to 275 you also need to cheange the fronts to 245.

Had Michelin PSS all the way around, got Ventus V12s for the rear, have always had a set of 4.. Anyhow, car became an unstable mess at high speeds by veering while turning, switched my PSSs to the rear and V12s to front, presto. Low profile tires in the front with high profile tires in the back work fine, in fact, maybe even better than the 4 PSSs…more time for testing will tell. However, I wish they made the tread pattern and traction of V12s but on the stability of PSSs. Does a tire like that exist?

The same thing happened to me this morning i bought new rear tires and i felt like my car was slowing down and then i saw my PSM light going on and off while it was happening. After i got i checked my lug nuts with a torque wrench and they were good. i'm glad it's just a matter of the tires breaking in.

Did you deviate from the tire sizes that your car originally came with? These symptoms will also occur if the computer is not seeing the proper front to rear rolling ratio that has been programmed in by Porsche , since there is a staggered tire size arrangement front to rear You don't have to get the exact sizes of tires , but going too far out of bounds causes the computer to be tricked into thinking that one of the tires is slipping, so traction control kicks in For example, if one of the front tires is smaller in circumference than the allowed threshold, it will appear to the car as if it is "slipping" because the rolling speed will be higher than the computer is expecting it to be

I have “mismatched” tires on front and rear and have not had PSM ever act up. You need to wear new tires in and not do any sporty driving while the oils/materials left from the manufacturing process are worked off. Tire manufacturers recommend a period (depends on the manufacturer/tire) without any dramatic acceleration, braking, or cornering. I suspect that’s what was causing OP’s issue, the rear tires don’t have the same grip because they’re brand new. Now with all 4 tires , they’re matching in the lower grip and PSM system isn’t detecting “slip” in the rear relative to the front.

When you get new tires , look up the manufactures recommended wear in period. Then drive gently throughout that period . Lay off the sport driving for a bit so your tires can wear in properly. I know it’s not fun, but it’s 1) safer and 2) will wear your tires evenly as intended.