KevinGross

I'd definitely begin with some pyrometer readings on the tires before drawing any conclusions.

Are ppl really running the R7's with that much hot pressure? I've been shooting for 33 psi.

Difool

Is it possible you have too much rear brake bias? If you are dragging your rear tires under straight-line braking you will wear the insides, and that will be worse when the tires are overinflated.

I’ve found the stock Cayman S calipers to have a bit too much rear bias and ran slightly less grippy pads in the back, up until this year where I increased the size of my front pads and now run the same compound on all 4 (achieving the same effect).

FFaust

A few years ago I had issues with R6's splitting between tread and sidewall so called up the factory for advice. They told me to shoot for 36 - 38 hot; never really bought the 38, but been running 36 on everything since, even the Hankooks.

jgiannone

I believe this is a toe issue. If you look at the alignment sheet, the spec calls for between .03 and .13. And your car is at the upper end of that spec, a spec that was set for a street car, on street tires, and at street ride height. If during the alignment, the shop can do a sweep and measure the toe during compression (bump steer and or roll steer), it would be interesting to see what happens to that static toe number.

CTS

That setting is also appropriate for a race car. No factory built Porsche race car has a spec of less than 12 minutes per side in the rear. You are correct that the roll steer could be screwed up.

Chris Cervelli
Cervelli Technical Service

jgiannone

Chris, thanks. Are there guidelines for toe in the factory rear-engined cars more specific than "no less than 12 minutes". If my math is correct, 12 minutes is about .05 inches, or again, at the lower end of the range. Along those lines, likewise for the rear engined multi-link cars, at greatly reduced ride heights, does the car toe in or toe out under compression (bump or roll)? Thanks for any insights.

cstyles

From Hankook Racing Tires in Florida, supplier for PCA SPC class:

Hi Chris,

Thank you for the information. I am glad you reached out to us, I want to make sure you are getting the best performance out of your tires.

Hankooks have stiffer sidewalls than most other manufactures, definitely stiffer than Pirelli. You should reduce camber to -2 deg. I can see from the tire photo that the center of the tire is collapsing a bit which tells me that you are running too low pressures. I generally recommend 36 psi hot for Z214. Start at 29-30 cold.

This tire is done, but in the future you can flip the tire on the rim to get more life out of it. If you have any other questions please don’t hesitate to ask.

The above advice is related to the rears, which I currently have set to -2.7 and worked great with Trofeo R's. So this feedback makes a lot of sense. I have mounted up a fresh set and will be targeting 36 hot, and will set the rear to -2.0 and the fronts to -2.8 (I noted the fronts were also wearing faster on inside edge when swapping to fresh set, but not as bad as rear). I'll update this thread after I've killed the next set with results.

Der ABT

You only get a 6 psi rise?

CTS

For the rear suspension, invariably they toe out in droop and toe in in bump. The front suspension is the opposite. It has to be this way to create some roll understeer. Roll oversteer is never desirable.

All factory race 911's that I am aware of (964 and later) use a spec of around 15 minutes toe in per side in the rear suspension. Some a little more and some a little less but 15 minutes is always close to the spec.

The OP will be switching tires once he finds that he is slower with less negative camber and only sees a tiny, if any, improvement in tire life.

Perhaps off topic but the Hankook Rs4 is an incredibly good tire. I don't want to characterized as a Hankook hater, but I think this is a case of the wrong tires on the wrong car.

Chris Cervelli
Cervelli Technical Service