ngoldrich

For the first time I just ran my 2001 996 TT at MidOhio. The car only has H&R lowering springs and Kuhmos and realignment(plus harnesses & a harnes bar).

A bit of warning - the shop that realigned it put -2.5 camber in the rear. It destroyed the kuhmos. They were blistered and chunked on the inside edge of the rear tires. The temp hit 260 very quickly. This all happened within about 15 minutes.

Fortunately a friend of mine who is a Porsche IMSA crew chief realigned the car at the track and I had 2 new rears overnighted to the track and mounted.

He changed the rear camber to -1.3 and that fixed the problem.

It must be that the new multilink geometry does not go through the same huge camber change as my older banana arm cars.

Anyone else had similar experiences ? Everyone else I have talked with also ran very little rear camber on a 996TT with track tires.

Any input is appreciated.

Thanks,
Norm

Hank Cohn

Norm:

I am surprised to hear about your Kumho experience. Which Kumho’s were these, the V700 Victoracers or the Ecsta V700s? I have not had an opportunity to try the new Ecsta V700s yet, but I have used the Victoracers quite a bit. In general, they seem to like a good bit of camber – from 2.5 to about 3.5 in my experience. Admittedly, I have never used them on a car as heavy or as powerful as your. Additionally, I don’t feel that Mid Ohio is particularly hard on tires. What hot tire pressures were you using and what was the approximate ambient temperature during the day. Did you experience a lot of wheel spin? Did you change your driving style between the two days?

Thanks for the write up,

Hank

Greg Fishman

Norm,
Where the tires shaved or full depth? I stopped by your garage a time or so and never got a chance to talk with you.
I have heard that you will get a lot longer life if these tires are shaved, maybe that is why you were getting such high temps and the chunking.
On a lighter car maybe you could get by with the full depth.
Greg

ngoldrich

Hank, Gregg,

Thanks for the input. I was running new Ectsa V700's. They were full tread depth (6 /32 ) not shaved (4/32).

I talked tonight with another person that had the same issue. The problem was that with -2.5 on the rear I could not keep the inner temp below 230 degrees no matter what tire pressure I ranand once went up to 260. The tire pressure grew dangerously high too (an increase in 20 psi 34 to 54). Once the camber was set at -1.3 the temps stayed reasonable and the pressure growth was normal.

I was pushing the car pretty hard but keeping from generating ch tire spin. 3500 lbs is a lot of weight to be pushing that fast, but I was not abusing the tires. I always watch my tire management, as it is mandatory in the IMSA & Grand-Am racing I do. I run both a CanAm & Viper GTSR. So you get pretty good at tire management, otherwise the tires will be gone in a few laps....

Anyways, if you have anymore thoughts let me know. 2 of my students had 996 TT - one with street tires and one with Hoosiers. Both were running -1.3 or less and both had no tire problems. And I drove both of their cars pretty quickly/hard with them in the cars and no tire problems.

Thanks,
Norm

PS - Gregg, sorry I missed you at the track. I had 3 students so I was busy most of the time...

Greg Fishman

[quote]Originally posted by ngoldrich:
<strong>
PS - Gregg, sorry I missed you at the track. I had 3 students so I was busy most of the time...</strong><hr></blockquote>

Likewise, and Friday I was in my car as much as possible. Boy did we get lucky with the weather.
Curious, did you notice your speed at the end of the straight. My friend instructed another 996TT and on his second session (ever) they were hitting 145. Who did you have mount the tires? Was it that new outfit that was passing the info around? That is great to have someone that can handle that type of stuff. Good for you that Jon was there also.
Greg

ngoldrich

Gregg,

I did have the new shop mount the tires. He was very nice. He stopped by, picked up the car, swapped the tires, and returned it...

Also, I kept my students at 130. I normally do that to teach them the importance of turn exit speed and not terminal velocity and entrance speed. All it does is chew up brakes and tires. They normally end up quite a bit faster through the next set of turns. Plus it's safer with me in the car :-)

BTW-Late braking I was hitting 149. But with 3500 lbs I only would do it a couple of laps...

Norm

Greg Fishman

I agree with the 130 limit. My friend must not have the same sense of self preservation.

Arthur

I thought it was a rule in DE's that students' cars are to be driven only by students, and that no "borrowing" is allowed. Is there a rule that prohibits one student from borrowing another student's car in a DE event?

Arthur

145 MPH! Whew! That must be a long straight, either that or those 420 horses are on amphetamines:-)

ngoldrich

Arthur,

Our region and many others do allow instructors to drive their students cars with the student in it. It is an invaluable learning tool for the student. It is a very good way to get students to the next level of ability. It is the easiest way to get 'A' students to get over some hurdles when they have plateau'd and cant seem to get to the next level on their own.

I believe you are correct, however, some regions do not allow it.

Norm

SundayDriver

Before I sold the TT, I ran a set of Ecstas. Previous track tires were Hoosiers. I usually ran 2 deg negative camber F7R, but changed the rear to 1.5 deg to make the car a bit more tail happy with the Hoosiers. With the smaller front tires when I switched to the Kuhmos (225 vs 245) I expected some understeer but got the same balance as the Hoosiers. My conclusion is that the Kuhmos work with less camber than the Hoosiers or the P-Zero C's I have also run. Your experience seems to also support that.

I am jealous of your outing at M-O, my favorite track. Last time I had the TT there, I was hitting just over 160 mph if I went deep. Very scary as the braking point is just prior to a rise and drop which really reduces the braking in a street car. I am trying my best to get out there this summer for a race and the TracQuest event.

ngoldrich

Mark,

Thanks for the info. Glad what I was experiencing seems to jive with everything I am reading and hearing.

Hope you make it to MidOh...

Norm