Greg H.

Is it possible to have too big a rear tire on a car? I have a 993TT and am using 315 R comp rears (the car came with 285). Is it possible the car would be faster around a track with narrower rear tires? I have a little more adjustment in the bars - I can go 1 holes softer in front and one hole stiffer in the rear. Which should I try first - bars or tires? I need new tires, is the reason for my question.

Greg H.

Veloce Raptor

tires

coryf

What size front tire/wheel? What type of alginment are you running? Track only or dual purpose?

M758

Sway bars are for fine tuning. You can use them to fix a handling issue, but that is a band-aid until you can fix it right.


It is possible to have too much tire for a car. However I am not about to say that is your problem because I don't know enough about you car.

Doc GTO

Ditto, more info needed!

Greg H.

I understand there are a lot of variables the most important probably being me. I was just trying to keep things simple. It's a dual purpose car, but the street driving mostly consists of driving to the track on the highway. I'm using Nitto NT01 245/315. Have Pss9 and TRG bars (which are relatively thick compared to what Porsche offers) I have a thread going on the 993 forum discussing alignment, but let me just say I am trying to align it to maximixe track performance. Camber at -2.3 in front which seems to work and -2.4 in the rear which I might lower based on wear and tire temps. -.15 total toe in front and +.5 total toe in rear (which seems a bit much to me).

Greg H.

e9stibi

What rim sizes are you running?

JustinL

Tire temps?

Greg H.

18" rims, 8 and 11

Not sure the temps are going to help. As was pointed out to me, the track i got the temps are is terrible for taking them because the tires aren't being stressed anywhere near the exit. The only thing of interest is that I'm getting the fronts up to 190 and the rears only up to 170 -175.

Greg H.

claykos

Where does it understeer? Corner entry, exit, middle, everywhere?

That tire temp distribution definitely points to understeer. Start with less rear toe in, go to 0 toe on the front or even a touch of toe out, and a bit more camber in front. See if that helps. Might need to do a spring change.

edit: I was misreading your toe settings, I think you already to have some toe out in front. So just go to a bit less toe in on the rear.

Greg H.

My complaint is mid to exit. Probably everywhere, although I am trying to trail brake more and more.

Greg H.

himself

FWIW, I run the same tire sizes on my 996 GT3 and I think 315 is not enough rear tire. I don't see understeer anywhere with this setup, but get oversteer pretty much every where, with rear on full soft and front on full stiff.

I would be concerned that you are using too much steering angle, which is causing the understeer and the higher temps. You might consider having someone ride along, or grabbing a ride in a car with someone who is versed in the NT-01. It's a different animal than a Hoosier R6 for sure.

-td

Cory M

more set-up info needed, but:

adjusting swaybars is free and takes about 5 minutes

993TT is all wheel drive, probably a big reason for the understeer

ubercooper

If your getting understeer than you need wider front tires... those 245s clearly not griping enough. Even newer GT3 come with 275 fronts and 335 rears

JustinL

Personally I would adjust setup before buying new parts, otherwise you may be chasing the same issue with a new set of tires.

First thing I would do is get a good tire temp reading with Outside, Middle, Inside for all 4 corners.

Do you have adjustable shocks?