[Sorry for the cross post -- but I'm not sure if this is more of a car/tire question, or track specific....]

I've got a question for folks who go to multiple tracks. I took my 996TT to Thunderhill Raceway for the first time and had a blast. However, I did notice that the PSM seemed to kick in more at Thunderhill than I've experienced at either Sonoma or Laguna Seca. In fact, I've never noticed the PSM kicking in at those other tracks.

Has anyone else noticed this at Thunderhill? I'm thinking it may have to do with the elevation changes and the several turns where there are hills and off-cambered slopes. Unfortunately, it's not apples-to-apples comparisons since I am running a new set of MPSS instead of MPS2 tires.

Here are some of my favorite pictures from the day -- the lighting and colors are pretty good in these photos:

 

Nice shots! No track experience here but my PSM tends to come on the most in bumpy downhill turns. Stock suspension.

 

Disconnect you PSM when you go to the track. Your rear brakes will thank you...

 

This is very true and more with grippier tires, I had my guy disconnect fuses for all PSM and ABS and ran slicks at our local track, wow I can't believe how much the systems hold back and control the car. I had him install separate switches for ABS and PSM so when I'm at certain tracks I can turn off and control one or both. It is a lot of fun. Did you try turning off your PSM button to see how different it would handle? Not completely removing it but little different for the taste...

 

I'll definitely try this out next time. Why does it kick in with more grippier tires? I might have guessed the other way. Maybe it's more about the MPSS tires than the track?

 

Aerodude,

What size Pilot Super Sports are you running?
Do they make them for the stock 18's?

Great Pics, have fun!


FBS

 

I compromised a bit on the MPSS sizes -- I got 235/40 and 285/35 tires -- A little wider in the front and a little narrower in the rear. Actually, I was looking to take out the understeer a little bit so this could work out well. These sizes fit the OEM wheels well and, although the diameter is a little bigger than stock, it's no problem at all unless your suspension is lowered by quite a lot. Another by product -- now my speedometer is only off by 1-2 mph .

 

You run with psm on? What exactly Is happening when it kicks in? sounds like you might be pushing the car harder to just now be feeling it kick in. That or trail braking more.


Also psm is more of an as needed protector. If you increase grip you increase yaw forces which puts psm on higher alert to react quicker. Grippier tires mean higher slip angles able while still having grip. PSM does not like.

 

When it's coming on (not all the time), it's typically when I'm accelerating out of a turn. At Thunderhill Raceway, there are several turns that crest over a hill so the car may also be unloaded at the same time. 2muchtime mentioned that grippier tires could cause this too? -- I just put on a set of MPSS tires to try out.

 

Read my edit.

 

Tires sizes aren't ideal that could be causing as well, the more aggressive and faster you start going into the turns, trailbrake, etc. the more you will find the interfence. Next time out after your warmed up turn off the button (but keep it in mind). My last outting @ Sebring turn 17 your going in @ 110 or so and I really noticed the PSM/ABS correcting the car, something you definitely have to get use to (able to completely turn off) in moderation but will def add more fun and speed as you progress. I finally realized after driving 997 cup car for the evening how civilized our TT really are - as well as excess weight.

 

What part of the tire sizes do you think is contributing? Is it the narrower rears, or slighty larger diameters? I was concerned about the narrower rears -- but thru some research and discussion with folks, I think it's ok given that I'm still on the OEM 11" rims. Based on the manufacturer specs, this adds about 0.2" to the effective tire width which results in about a 5mm (rather than 10) difference between 295 and 285 tires. I did make sure the front/rear dia are with spec, but the tires are definitely taller by about 3/4". Thanks for the ideas on this. I'll know a lot more when I run these tires at Laguna or Sonoma where I'll have a direct comparison with prior experiences.

 

[QUOTE=Aerodude;3830618]What part of the tire sizes do you think is contributing? Is it the narrower rears, or slighty larger diameters? I was concerned about the narrower rears -- but thru some research and discussion with folks, I think it's ok given that I'm still on the OEM 11" rims. Based on the manufacturer specs, this adds about 0.2" to the effective tire width which results in about a 5mm (rather than 10) difference between 295 and 285 tires. I did make sure the front/rear dia are with spec, but the tires are definitely taller by about 3/4". [Quote]

Could be? Stock recomended on 8/11's are 25.1 = 834 +/-

You are stretching 235 recomd 8.5 @ 25.4 = 819 remember stretched so slightly off and 285 recommend 10 @ 25.9 = 804 really stretched??

Your next progressive set try the pilot sport cups, I know there $$ but the 225 & 295 are ideal sizes and after scrubbed really run to their potential. I ran them at Daytona with the steep banks and fast turns and rarely saw PSM lights. The progress to slicks .

It's really good your paying attention to the warnings and feeling of the car on the track -

 

I believe your tire choice is causing you problems...

My car has a tendency of rear brake use even with PSM off, especially in weightless situations such as certain turns at THill and CS @ Seca.

 

PSM is by far the most conservative traction control system I've ever experienced. This is the first car where driving aids kick in on canyon driving.