peter_964rs

I'm a bit of a track day fiend and have a nice 964RS lightweight onto which I managed to fit a set of Pirelli PZero type C ex-Porsche Cup tyres earlier this year.

They seemed to be wearing quite well, I've been to the Nurbergring on them, Spa, Donington, a few airfield days, but just recently I noticed that the left front was getting more worn, especially on the outside edge, which is softer rubber of course. After the last airfield day last Saturday to my shocked surprise I saw the left front was completely bald and bits of canvas, underlay, whatever the stuff is were showing through.

Er........

All other three tyres absolutely fine, plenty of tread, all tyre pressures the same (I vary between 32psi and 36psi hot and always check after use in a session).

First, these tyres are a bit interesting, the Pirelli Type C is no longer manufactured but there were some still available at the beginning of this year, if you knew whom to ask! Anyway, as I was unable to get my hand on the Pirelli Corsa R or the Michelin Cup tyre at the time, the ones I managed to find were Pzero type C "dry", but hand-cut for wet use and, strictly, illegal on public roads (oops).

Well, they were grippier than the Michelin road tyres I had on before if not quite as good as "stock" Type C's - let's just say I had some interesting experiences with them - but after several track days this year I was pleased to see that the wear rate wasn't too bad, and I generally don't hold back at these events....!

Anyway, it seems to me that the degradation of the front left is sudden and definitely out of character. The last three tracks I've been on have all been run clockwise, with predominantly right hand bends, which is fairly normal IMHO.

I'm a little concerned that some other (probably expensive) component failure, or possibly suspension setup, has caused this excessive wear and needs amending. So is it likely to be:

1) A duff tyre - just buy another set of something else, probably the MIchelins which are now homologated for road use and fairly cheap to buy.
2) Suspension setup - I do feel that the car is suffering too much from understeer and I usually have to pull the rear around a corner with a bit of dangerous tail-braking. When I first noticed this wear it was the outside of the left front that was wearing first, as though the car was rolling over the top of the tyre and scrubbing off loads of rubber.
3) Suspension failure of some kind whcih I haven't picked up on, perhaps a duff shock?
4) Finally, I have to admit to having an aftermarket rear wing, GT2-style, and some front aero-strakes under the chin to push the front end of the car down and counteract the understeer a big rear wing can produce. Is this the likely cause, and is there anything I can do to the car to fix the situation?

Any advice gratefully received......

Adrian

When you hit the curves and corners do you get the feeling that the rear seems to be pushing the front around. If so this is an indication of not only massive understeer but also of an out of balance situation. I would recommend a check of camber, ride height levelling and general wheel alignment.
On the 964 RS you can try and dial some understeer out by adjusting your rear sway bar,
Ciao,
Adrian
911C4

PS: Of course it could be simply that the tyres have gone off and they need replacing.
Pirelli Zero Cs are tought to get but I believe there are still stocks in and around Geneva Switzerland.

JBH

It is definately time to get the car cornerbalanced and aligned. While having that done, have your mechanic check all suspension parts and connection points to ensure they are tight and in good condition.