GrantG

I guess that means if you toast your tires at the track, you can still limp home on the road pretty easily (when going straight, -1.5 degrees of camber is enough to ride on the inside harder compound).

Earlierapex

anyone try less camber with hoosiers to try to move the wear laterally? It's unconventional, but only 4 or 5 sessions is more economically stupid than Gillette's ill-advised attempt at social justice warrior shaming their best customers..

nolimits

This thread may be of interest re R7 wear issues.


https://rennlist.com/forums/racing-and-drivers-education-forum/1097514-have-r7-s-changed-disturbing-grooving.html

TRAKCAR

Earlierapex

TRAKCAR

Earlierapex

Circling back on this after talking with John at trackdaytire.com with a couple questions if you don't mind? Even though it's ideal for hoosiers, wouldn't more neg camber make this worse? Also, wouldn't toe-in cause accelerated wear on the outside of the tire, so this is likely a toe-out issue? The only problem with this theory is that the inside wear is worse on the driver rear than the passenger rear, so there's really only 1 high load corner at Sebring (T1) that would have toe-in on the driver's side...

Could this maybe be trailbrake related which I think causes extra toe-out? I TB heavily - anybody know what RWS does under TB? If it is in-phase steering, the inside tire may be getting a huge double dose of toe-out under braking and in-phase steering?

A/S

As I stated before, the wear is due to excessive toe caused by RWS, and it cannot be fixed. No matter what you do for static camber, or static toe setting to your 991 GT3, the Hoosiers will continue to wear like that at Sebring, and it is not a Hoosier tire problem, it is RWS and its 1.5deg of camber change.

It could be fixed if you find a way to disable RWS. And, if you find a way to disable RWS, Andreas Preuninger is on record saying that RWS is the equivalent to remove 100Kg from the car (220 lbs) or add 68 Hp, you'll be back to 997.1 GT3 lap times. Disable RWS (if that's even possible) and your Hoosiers will last just another day (they will cord in and out in 16 track sessions anyway).

RWS, combined with the cheese-grater surface at Sebring and the track layout at Sebring accelerate the wear. The places where this wear is worse are T1, T6, T8, T9, T11 and Bishop's bend. On your next track outing, place a GoPro facing to the rear tires (I did) so you can see the RWS system at work. It is in these high speed turns where RWS is working but the car is dragging the tires with excessive toe (it doesn't matter if toe-in or toe-out, rear tires are being dragged) at high speeds. You could reduce the wear at Sebring, by setting the rear camber to something like -0.5 degrees, but they will wear fast anyway, as they are being dragged for too long at something in excess of 15mm toe per tire, massive toe.

If you want the most predictable (and easier to drive) alignment, the alignment specs need to match the tire/wheel, the racetrack, and the driver. Most GT3s driven out there would be fine running less than 1 degree of camber, because those drivers park their cars at every turn, then go all-out on the straights. Their alignments need the best contact patch on straight line, and that requires 0 camber, as they are great on accelerating and braking on straight line. There are better cars than a GT3 for the point-and-shoot drivers to produce better lap times for them.

I'm a little slow at Sebring, my best laps there are 2:15s in my 2016 RS on these Hoosiers (295/345). I run my cars at Homestead, PBIR and Daytona most of the time. At PBIR my Hoosiers are happy, at Homestead too, at Sebring they cord the inside as your first pictures (I don't let my tires get that bad, I inspect them before every session). At Daytona, I avoid Hoosiers as they cannot handle the downforce and the rear weight in the 991 TTS and 991 GT3 RS, at this place only MPSC2 or TrofeoR.

I went through 9 alignments in my .1 GT3 RS, as I try to optimize the car for a specific set of tires/wheels. Started with -2.5 camber all around, different front and rear toe settings, eventually ending in -4.0 camber front and -3.2 rear. I have to start from scratch with the 991.2 GT3 RS, as the spring rates are drastically different and the car has full monoballs, but for Sebring that wear will continue. I'm going to test Michelin slicks next, as Hoosiers are letting me down a bit on track days (the things love rotating on the wheels, and my car only keeps the wheel balance for one session, I don't even balance my track wheels anymore).

krell

Good technical information.

A shop near me that does a lot of setup work on GT cars says they run zero toe in the rear. Any possibility this would mitigate the issues we're discussing on a car with RWS?

A/S

Nope, it won't. When the rear wheels turn, they turn 1.5 degrees. These cars don't use a lot of static toe-in from the factory, Porsche has been using 0.25 degrees per rear corner for ages. 0.25 degrees is pretty small, 1.5 degrees is 6 times that, and that's what RWS would do. 991 Turbo S: 3 degrees, I once corded a set of 315 rear Hoosiers in 26 laps (3 track sessions at Sebring in my TTS).

Earlierapex

A/S - again, very helpful, thank you. For backdrop - you aren't slow at Sebring, and I'm not a point and shoot guy either - have 20+ years of club racing and DE experience - run low 2:20's on MPSCs and upper teens on hoosiers in a completely stock 2014 GT3.

The super-hard interior rubber of the MPSCs makes a lot more sense given the toe-induced wear. Also makes sense why extra neg camber doesn't help as much with those specific tires.

I suspect trailbraking is making this worse, but it sure is fun and smooth to left foot brake and transition to the gas while still under braking. Hope to see you out there.

CALSE

Inside face cording on mine also.