PSM issue, Any input ???
#1
Thread Starter
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PSM issue, Any input ???
Hi,
Last weekend i drove a DE at Watkins Glen and i had an issue with my 2001 996 turbo with a Tiptronic transmission. The PSM was kicking on in places that it should not have been on at all. This is not my first event i have been doing DE's for three years now with this car and it has NEVER happened before. For the rest of the event i simply shut off the PSM and the car was fine. This car is well maintained.
One of my good friends asked me if i had done anything to the transmission. Last fall after my last DE i had the transmission flushed. The car has (52k on the odometer). He thinks that maybe they did not follow proper procedures when changing the fluid. My guess is that i'm going to have a difficult time proving to the shop that they caused the problem.
The only other thing i did to the car (other than oil changes and flushing the brake fluid) was installed new rear tires (proper sizes all Hankook V12Evo) the fronts still had more than 60 % tread life.
Any help would be greatly appreciated.
Regards,
George
Last weekend i drove a DE at Watkins Glen and i had an issue with my 2001 996 turbo with a Tiptronic transmission. The PSM was kicking on in places that it should not have been on at all. This is not my first event i have been doing DE's for three years now with this car and it has NEVER happened before. For the rest of the event i simply shut off the PSM and the car was fine. This car is well maintained.
One of my good friends asked me if i had done anything to the transmission. Last fall after my last DE i had the transmission flushed. The car has (52k on the odometer). He thinks that maybe they did not follow proper procedures when changing the fluid. My guess is that i'm going to have a difficult time proving to the shop that they caused the problem.
The only other thing i did to the car (other than oil changes and flushing the brake fluid) was installed new rear tires (proper sizes all Hankook V12Evo) the fronts still had more than 60 % tread life.
Any help would be greatly appreciated.
Regards,
George
#3
#7
Race Director
However, I have never tracked the car. But it has seen some mountain road usage...
In any case, I do not think the different diameters are to blame as I think you would get a warning even on the street, but on the track grip differences -- as 02996ttx50 mentioned -- might explain the behavior.
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#8
agree it doesn't sound like rolling diameter issue ( though in fact, it is.. hence the cel! ) but rather the ecu detects the new vs old fairly easily. it might also be exacerbated by the very real fact that v12 tires are greasy. once you really scrub them, i would think the psm should settle down. but my dislike of hankook v12's has been widely debated in here. so i'll leave that part out. whoops. lol. i'm sure they'll be fine.
most of us probably go thru 2 sets of rears to one set of fronts. ( maybe even 2.5 sets of rears ) and the only time i feel i'm matching too much rubber ( new rears ) against too little ( older fronts ) i get abs/psm activations and cels. but i match my tread depths fairly closely for both aesthetic and practical handling reasons, so it's a rare event.
most of us probably go thru 2 sets of rears to one set of fronts. ( maybe even 2.5 sets of rears ) and the only time i feel i'm matching too much rubber ( new rears ) against too little ( older fronts ) i get abs/psm activations and cels. but i match my tread depths fairly closely for both aesthetic and practical handling reasons, so it's a rare event.
#9
Thread Starter
Advanced
Point taken. On the road the car is fine. Didn't get a CEL only the PSM light. My durametric tool showed no faults. Damn i wish i would have stuck to my guns and bought a manual trans car but the price was right.
Once these Hankooks wear out i will be looking for something else. Not sure what to get yet, will do the homework before my next purchase.
Probably preaching to the choir here but what a car.......... drive it to the track and flog the heck out of it for three days then turn on the A/C and drive it home again.
Thanks again for the help.
George
Once these Hankooks wear out i will be looking for something else. Not sure what to get yet, will do the homework before my next purchase.
Probably preaching to the choir here but what a car.......... drive it to the track and flog the heck out of it for three days then turn on the A/C and drive it home again.
Thanks again for the help.
George
#10
Rennlist Member
You will get the PSM kicking in regardless of tire make if it detects one or more tires rotating at a different speed. If your fronts are worn and you put on new rears the PSM will kick in depending on the difference. V12 have a little bit more tread depth than some other tires when new. I would suspect that once you put a few miles on the rears and the tread depth comes down, the PSM will not be an issue.
#11
^ that's absolutely true. as is the reality that as tires go, v12's are even more squeamish when new, than most other tires. which might even temporarily increase the cars propensity toward abs/spm cels, again, until scrubbed.. though you might differ with me on that point.
...george yes, amazing car, no doubt!
...george yes, amazing car, no doubt!
#12
You will get the PSM kicking in regardless of tire make if it detects one or more tires rotating at a different speed. If your fronts are worn and you put on new rears the PSM will kick in depending on the difference. V12 have a little bit more tread depth than some other tires when new. I would suspect that once you put a few miles on the rears and the tread depth comes down, the PSM will not be an issue.
Not sure what PSM makes of that situation but I know my PSM is very sensitive to mismatched wheels (ran some 10 inch rears for a few days while my 11s were being coloured up) and also to having any underinflated tires.
I normally just change all 4 tires at once with matched sets, but you could test the above theory perhaps by raising your fronts a few PSI and dropping the rears by 3 or 4 to better even up the rolling diameters. You may not want to keep running like that for long but for the short duration of the test you'd probably just see a bit more understeer than usual.
#13
#15
Rennlist Member
996tnz - not sure your observations are correct. The Michelin PS2s N spec tires, 225-40ZR18 has a diameter of 25.1, and the rears 295-30ZR18 have a diameter of 25.0. Hardly enough to make a difference.