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I'm betting you are also on a stock open diff. Install a proper LSD with a 60-80 lb preload and that will be a game changer. Car will be much more stable under braking and aceleration which will drastically reduce PSM intervention. With a properly set up chassis (stable car) PSM will became all but unnecessary. Finding someone that can actually properly dial it in is a challenge however. Good luck.
Used tires are a crap shoot. They can be of varying degrees of grip. I have bought from JB before, I bought tires to see if 275 would work on the front of my car and 335 on the rear without having to spring for a new set. Man! Car was ALL OVER THE PLACE. After many setup changes we figured we were "chasing tires" meaning the varying grip on each corner was ruining handling. Sure enough, won some new sets and problem vanished......
That, my friend is likely more of the answer to your problem than any of the other stuff. PSM is like "WTF?"
You need to start from scratch bro. Just got rid of a ton of tires that had the exact same wear per corner or I would have offerred up something.
BTW, any reason you dont try a 315 hoosier? Why would you up the stock front size and not the stock rear size? Even that will create an imbalance, even with the same grip level per corner (relatively speaking due to size reference)
Last edited by heavychevy; 06-01-2016 at 01:54 PM.
I was down at Mid Ohio yesterday with Chin Motorsports for a one day HPDE event. I've recently made some changes to the 996TT:
1. Coolant lines pinned.
2. Swapped stock control arms to RSS dogbones/control arms.
3. Put new Hoosier R7 tires on the front. Rears were in good shape so they were not replaced.
4. New RSS engine mounts.
5. My shop aligned the car.
As the car was unloading through several of the turns, the PSM light would kick on & it would almost like the car was fuel starved for a split second. It has never done before at the track (other than when I did something stupid).
Could this be a situation where I need to also replace the rear tires. Currently I am running Hoosier R7 245/35/ZR18 fronts & 295/30ZR18 in the rear.
Today I went through the national instructor school that PCA put sign down at Putnam Park. I replaced the rears with new Hoosiers (295/30ZR18) and the car behaved much better. I still want to go with the taller front tire to evenly matched it to the rear but I ran out of time. My shop is going to have to slightly raise the front to compensate for the taller tire. I want to get this done when I get back into town this weekend as I will be instructing next weekend at mid Ohio
Last edited by viprklr; 06-03-2016 at 08:25 PM.
Reason: Spelling
Today I went through the national instructor school that PCA put sign down at Putnam Park. I replaced the rears with new Hoosiers (295/30ZR18) and the car behaved much better. I still want to go with the taller front tire to evenly matched it to the rear but I ran out of time. My shop is going to have to slightly raise the front to compensate for the taller tire. I want to get this done when I get back into town this weekend as I will be instructing next weekend at mid Ohio
Thanks guys for the feedback. I think after this thread I'm convinced it was a combination of older rear tires (purchased a set of used rear Hoosiers from John Berget as backups) along with the fact that I put a new set of Hoosier with the wrong diameter. I am headed to Putnam Park tomorrow for a 3 day DE event & want to make sure I am safe. I contacted Hoosier Midwest & they are going to install a new set of fronts (245/40ZR18) & (295/30ZR18) tomorrow afternoon on the way down. Hopefully this will rectify the situation.
I saw you out there! I was in the dark blue 996TT with the orange tape on the headlights. Meant to come say hi.
Bringing back an old thread. Just replaced my rear tires Michelin Pilot Sport 4S 295/30/18, same as fronts except size.
Any time I'm in a medium-high speed turn the PSM is kicking in. I've never had this happen unless near the limit and it is doing it now no where near the limit (i.e. on-ramp). Interestingly I was in an empty parking lot today doing tight turns maybe 25-30mph it didn't kick in but on the way home hit a long 90deg curve about 45-50mph and it did kick in (it'll do it left or right turn).
As a side, the shop did not touch the car I dropped off the wheels loose and installed myself. I triple checked torques and pressures....stumped.
on edit: I noticed the rain channel width is significantly larger on the new tires than the old ones (i.e. loss of rubber contact patch across the entire tire width)
06-01-2016 | 01:24 PM
