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Tyre wear

Diggermeister

Well-known member
Joined
26 May 2015
Messages
663
The treads on the Cup 2s fitted to my 997.1 GT3 all seem to be wearing bang on level across the width of the tyre.

Car's mostly used on track, and I'm fastidious with checking and dropping pressures in first few sessions.

Is this good geometry, or am I not trying hard enough? What should I expect to see?
 
are you running an OEM suspension geometry i.e. how extreme is the camber ?
 
911UK said:
are you running an OEM suspension geometry i.e. how extreme is the camber ?
No, it's on more track focused geometry. Not severe, but not standard.

Not got settings to hand right now, but more camber than standard, for sure.
 
Diggermeister said:
911UK said:
are you running an OEM suspension geometry i.e. how extreme is the camber ?
No, it's on more track focused geometry. Not severe, but not standard.

Not got settings to hand right now, but more camber than standard, for sure.

Basically the geo you have matches your driving style, I expect your on about 2 or 2.5 degrees of camber.
 
Diggermeister said:
Is this good geometry, or am I not trying hard enough? What should I expect to see?

If your running to little camber the outer edge will wear and the little Michelin man will be missing from the side wall.

To much and the inner edge will wear out first. The cup 2 have different compounds across the width so this can hide the in balance.

But you must know all this being an ex hill climber no?
 
Just checked: 2.3 front, 2.2 rear.

Hillclimbs/sprints are a hell of a lot different: you start with barely warm tyres and rarely, other than on big circuits like Goodwood, generate much heat. Plus it was over ten years back and not with 911s.

Will be interesting to see how wear goes on hotter track days.

Michelin man still visible.
 
Diggermeister said:
Just checked: 2.3 front, 2.2 rear.

Hillclimbs/sprints are a hell of a lot different: you start with barely warm tyres and rarely, other than on big circuits like Goodwood, generate much heat. Plus it was over ten years back and not with 911s.

Will be interesting to see how wear goes on hotter track days.

Michelin man still visible.

You normally see a bigger diff front to rear than .1, interesting do you get much push? Once you put more camber on the car than you have, you end up with inner edge wear as the to and from track hammer the inner edge. Plus any more camber also really puts the car on a knife edge when it's wet I find. It's all a compromise some where down the line.
 
Push how? On power exiting a corner?

Thinking about the sprints, a lot of stuff was quite 'fixed'. We had custome Nitron dampers, but had to use standard wishbones, so nowhere near as much adjustment as a GT3.
 
Diggermeister said:
Push how? On power exiting a corner?

Thinking about the sprints, a lot of stuff was quite 'fixed'. We had custome Nitron dampers, but had to use standard wishbones, so nowhere near as much adjustment as a GT3.

Yes coming out of corner under power, what size fronts 235 or 245.
 
cup 2 wears very evenly and last ages. great tyre really. you could get away with 3.5 on the front and it wouldn't make much difference to wear IMHO. may tram line a bit on the street but definitely help on circuit.
 
Cunno said:
Yes coming out of corner under power, what size fronts 235 or 245.
Doesn't feel like it's pushing, but perhaps I've not yet got it on track on a dry day to lean on it enough. On 235s front.

Senoj said:
cup 2 wears very evenly and last ages. great tyre really. you could get away with 3.5 on the front and it wouldn't make much difference to wear IMHO. may tram line a bit on the street but definitely help on circuit.
Thanks. With current settings, it's lively but not twitchy. I might try a bit more camber next time round to see how I get on. I don't really care too much about road use, other than I just want to be able to get to and form the track in one piece. Driving fast on public roads isn't really my thing.[/i]
 
Diggermeister said:
Cunno said:
Yes coming out of corner under power, what size fronts 235 or 245.
Doesn't feel like it's pushing, but perhaps I've not yet got it on track on a dry day to lean on it enough. On 235s front.

Senoj said:
cup 2 wears very evenly and last ages. great tyre really. you could get away with 3.5 on the front and it wouldn't make much difference to wear IMHO. may tram line a bit on the street but definitely help on circuit.
Thanks. With current settings, it's lively but not twitchy. I might try a bit more camber next time round to see how I get on. I don't really care too much about road use, other than I just want to be able to get to and form the track in one piece. Driving fast on public roads isn't really my thing.[/i]

I found that once you go over 3 degrees on the front on my GT3 the car becomes extremely twitchy in the wet and very scary on public roads again in the wet. Currently on 2.85 degrees front which so far seems ok, wonder if wider track of RS helps in this situation as I couldn't run those cambers Dan has quoted.
 
Diggermeister said:
Cunno said:
Yes coming out of corner under power, what size fronts 235 or 245.
Doesn't feel like it's pushing, but perhaps I've not yet got it on track on a dry day to lean on it enough. On 235s front.

Senoj said:
cup 2 wears very evenly and last ages. great tyre really. you could get away with 3.5 on the front and it wouldn't make much difference to wear IMHO. may tram line a bit on the street but definitely help on circuit.
Thanks. With current settings, it's lively but not twitchy. I might try a bit more camber next time round to see how I get on. I don't really care too much about road use, other than I just want to be able to get to and form the track in one piece. Driving fast on public roads isn't really my thing.[/i]

I found that once you go over 3 degrees on the front on my GT3 the car becomes extremely twitchy in the wet and very scary on public roads again in the wet. Currently on 2.85 degrees front which so far seems ok, wonder if wider track of RS helps in this situation as I couldn't run those cambers Dan has quoted.
 
Yes, I get what you mean.

Certainly, on the trip to and from Spa or the 'Ring, I'm already a bit less relaxed in the GT3 than I was in the 996 turbo when it's wet. That would be a long old journey with a really twitchy car.
 
Having tried many, many geo settings on my 996 over the years, (everything from 2 to 4.5 degrees at the front & up to 3 at the rear), I have concluded that the optimal setting for my car & my driving style is around 3.1 F & 2.6 R with 15 minutes of rear toe & zero front toe. That's with 80N/mm front springs & 140N/mm rears with Moton Clubsport dampers and fairly stiff ARBs. Being on solid monoballs means the settings barely change during the year unless something wears out.

Set up as above, it's perfectly controllable in the wet & it can wear slicks, wets or any number of different types of road-legal tyres fairly evenly. Despite what many people think, the biggest killer of the inside edge of rear tyres is actually poor rear toe (either due to the static setting or worn toe adjusters allowing it to move under load). Investing in locking plates & motorsport rear toe arms will save a fortune in tyres and also impart great confidence in the grip the rear end has as a result.

I have 150K miles / 226 trackdays in this car so I am speaking with a fair bit of experience behind me. The fundamental GT3 suspension platform is largely unchanged on the 996/997 models & the Kussmaul settings are always a good reference point to start from.
 

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