"02996ttx50

lord have mercy jumper!

what did i say?

"probably because disabling with the dash button has to be repeated continually every time after you tap the brakes if you want psm "off". eg it doesn't "stay" off."

but i DO want it to stay off! "off" so i stay off the brakes lol. but thanks

"02996ttx50

"psm off" in whatever technical configuration ( dash button or full time "off" ) is for those for whom psm is intrusive to the point of disconcertion.

while it can save a novitiate that has overreached their limit, it conversely interferes with those that know how to operate the car near its "limit".

i've been driving and immensely enjoying the infamous tail wag of 911's for nearly + 45 years and although psm has indeed "saved" me in my first turbo 911, as i was initially learning the cars "limits" - or to the lessened degree - those i could even reach. i find the drive with psm "disengaged" always that much more enjoyable, especially when pushing it.

i do agree though. "psm off" is not for beginners.

that said: rwd tailwag with psm off is a gas

jayzbird

I had some horrible PSM intervention at Laguna when I replaced both NT01 rears after one caught a nail but kept the 50% used fronts. I never would have guessed it would make such a difference. On evenly matched tires PSM was really only a problem in one turn vs. almost every turn with the differently-aged tires.

jumper5836

I meant PSM doesn't reactivate and require the dash button to be pressed again and again after using the brakes. Like your post implied. PSM activates only while the brake is depressed and deactivates again while your off the brake. So you only have to press PSM off once.

Third-Reef

PSM on when driving near the limit is also reputed to roast the rear brakes. Some have stated that their nice red calipers were overheated to the degree the they turned brownish. The PSM system does a lot of its work with the rear brakes.

"02996ttx50

really? that hasn't seemed to have been my experience. i'll try it again now and then i'll have another beer. thanks.

Mike Roblin

I can confirm that it definitely has a tendency to cook the rear brakes as many of the heavily tracked cars at Sebring have burnt colored red rear calipers. Though, Sebring is really hard on brakes with 6 heavy braking zones with not a whole lot of space between them for cooling with the lone exception being the back straight from 16 to 17.

Also, I originally started my track work in a '79 911 SC so I do understand car control without PSM as that car you had to work with the seat of your pants and the hand/eye/foot control to keep it pointed in the right direction LOL.

Looking forward to getting two new fronts and seeing how much better the car behaves...

996TWINS

My advice:

Dump the R888's for NT-01's
Alignment
Front and rear adjustable sway bars (GT2/GT3)

DaveCarrera4

^ This. Rears are rust red, fronts, guards red from a day at Mid-Ohio. Disconnecting this year. Last year just hit the button.

jayzbird

People often overlook brake cooling ducts for the rear. I have the GT2 rear ducts and don't have many problems with the rears (the fronts, I do) getting cooked at Lagua, another hard track on brakes.

"02996ttx50

have done that. now with nt01's i have more inadvertent psm intervention than i ever have with any other rear tires previously run, though this is my usually off camber canyon stuff. its fairly dramatic though, and strange. though it is a stark reminder to disable psm! even if only temporarily.

here's an option for proving some extra cooling to the front. coincidentally, it's a diy option that the shop i favor ( and 996twinn's uses as well? ) offers. though you'll have to replace the hoses about once a year if frequently cutting tight corners if your car is lowered. tracking they will last far longer.

powdrhound

New NT01s are very slick and take a full track session or two (30-60min) to scrub in and provide optimum grip. You have to get some texture in the tire before it begins to grip. You also need to add some heat to them so don't expect these to work well in lower temperatures. It normally takes at least two laps to do that. NT01s are very slick in colder temps especially when you start to approach freezing. They work well at 150-170F tread temp and gradually begin to fall off after that as temps go up. Approaching 200F they become very greasy. Just my observation.

Tire pressure also plays a part. 32F/33R is where I find these to provide optimum hot grip. That means starting at 30 or so cold for street use. Higher than that and they will feel slick. My guess is you are running higher pressure Mark. This is a common mistake with these tires. At the track I start these at 24-25 psi.

These are great tires with the caveat that I never cared for the 315/30/18 size in these. I really liked the 245/305 combo but it's not AWD compatible.

"02996ttx50

thx for that info, john. i am going to lower the tp a couple psi from my usual 39 rear, and see if it "settles" down. based upon what you suggest the tires could well be "overinflated". i am rwd and haven't had psm issues at all since disconnecting the front diff and installing the w'trac and this psm "intervention" with relatively new nt01's is significant and unwelcome. so i'll begin with the TP see if this helps.

i think also your point about tire temps is probably dead on as well. thx again.

Mike Roblin

So, an update to this thread now after a weekend at Sebring. I replaced the old front tires with new and headed out on track with PSM still engaged for my first session of the day (figured I would try it at least one more time). Car drove better than before but was still having issues with PSM cutting in at very unusual places. Going down the back straight on lap 3 or 4 finally reached over and pushed the button, and what a difference that made!

Finally the car was driveable again, with predictable handling, great drive out of the corners and it was just so much more stable in all situations. Hard to believe that a stability control system could be so bad... The proof was in the feeling, but it was just as apparent with my lap times being about 3 seconds a lap faster without PSM! I can't wait to see how much better it gets after I put the suspension on the car in the next month or so...

Carlo_Carrera

Also keep in mind that the new tires on the front will need to heat cycle to match the grip of the rears.