Carrera GT

I'm just mounted Pzero Corsas on my "track day" car. I bought the tyres at Tire Racket and had them shaved to 4/32nds and heat cycled. They sat in the garage for a week before being mounted along with an alignment at Roger Kraus. So far, so good.

The problem is the apparent premature wear of the tyres, especially at the outside shoulders front and rear. The centre of the tyre seems to be almost new. The fronts have also gone out of balance -- they turn nicely to about 60mph but by 80mph the vibration is a problem at 100+ it's bad enough to prevent me from going faster.

They've had three days max on the street and one day at Laguna (last Monday) with approx 85-90 degree weather.

I don't (yet) attribute the wear to underinflation because I was meticulously careful with pressures, they've also only seen one day on the track and that was a hot day, so pressures were always on the high side. Plus, they've done 100 miles on the street and perhaps 200 miles on Laguna in one day.

The car is a 993 Turbo set up just for private track days on factory hollow spoke wheels (8x18 and 10x18) running -1.7 and -2.2 degrees of camber front and rear. The suspension is Euro spec 030. The car has 5000 miles on the suspension.

In my opinion, the handling is very good given the limits of the suspension to handle 450hp+ and the traction is good (although below my expectations from previously driving RA-1's) but the wear on the tyres suggests I'll be lucky to get two more days on the track. At $1500 a set, that's out of the question for my budget.

I've tried to follow advice from others in terms of temperatures and pressues, running 34 and 36 psi hot front and rear. Often the fronts would come in at 36 hot, the rears got up to 38 (trying to chase down those pesky GT2's ...) but the tyres never exhibited tendencies that might suggest over-heating, under- or over-inflation. In fact, until I noticed the degree of wear during an oil-change this weekend, I was quite happy with the tyres at the end of the first track day.

Thoughts? Advice?

At present, I'm thinking the tyres really need more camber and more pressure. I've contacted Tire Rack and they're willing to look at photos but no warranty unless they see the tyres have really failed. I'm not holding much hope there. On Wednesday at Laguna, I'll try to run the tyres as high on pressure as possible until I see the temps get over 200F. It also looks like being a cold day, so conditions will be all the more difficult to gauge.

I wish I could get MPSC or RA-1's to fit. Grumble.

Dennis K

I was at Laguna last Monday with Unlimited Laps too. My car was the black, track-prepared 928S4. I also have the Pirelli Corsas on my car. I am ready to give up on them. My story:

I put unshaved Pirelli Corsas (235/40/18 f, 265/35/18 r) on my car back in July and ran a DE day at Thunderhill. After five 30 minute sessions, I had terrible chunking problems with the outside shoulder of the front tires. At the time, I had -1.8 deg. camber in the car and I associated the problems with that. I ran at 32 psi hot and adjusted up from there as the center of the tire was not hot enough. I never saw temps higher than 195 deg. F on the outside shoulder however.

I had the front camber upped to -2.8 deg. and ran two DE days at Buttonwillow (different direction each day) and the chunking was nearly solved, but it ended up cording the inside shoulder with almost a flaking pattern to the inner half of the tread. Again temps were about within 180-195 along the width of the tire running 34 psi hot.

As the fronts were corded and the rears were still in good shape, I ordered another set of fronts, but shaved this time. I had the camber reduced to 2.1 deg. and went to Thunderhill. Again chunking, but at about 20% of the rate as the first time.

However when I went to Laguna with Unlimited Laps, the chunking continued even after the heat cycles of T-hill. The tires are looking pretty grim and look like I may only get one, maybe two days out of them. One of the 996GT2's at Laguna that day was also running Corsas and again I saw the same chunking pattern on his front tires as mine. He mentioned his tires were shaved and had been watching the pressures pretty closely. Maybe Arnaud will jump in here and relay his review of these tires.

I've pretty much given up on the Corsas and will try Toyo RA-1's next. They supposedly have a 245/40/18 size that comes from their Japan-only R1-R Trampio tire. Also if Michelin releases a 235/40/18 Pilot Sport Cup, I may give those a shot.

Carrera GT

I think we're seeing the same thing and I think I can speak for Arnaud in saying these tyres are trouble. I think you're right that the camber is critical and it seems like around 2.0 degrees works on the track, but of course the tyres end up riding on the inside and wearing out prematurely. Frustrating. I'm sending pics to Tire Rack, they've agreed to look at the problem. I'm going to push them to replace these things with MPSC's (I don't think Tire Rack supplies Toyo) even if I can't yet get the 235's on the front.
If you can source Toyo's cheaply, let me know.
Also, I hear the RA-1 or some variant is the spec tyre for ALMS next season.

Palting

Wow. Good to know. Thanks. I guess its MPSC's for me. Cheaper too.

Greg Fishman

No spec tire in the ALMS, can you imagine a DOT tire on a Audi R8?

The RA-1 is the spec tire for the Speed World Challenge GT class this past year and will be for the touring class next year also.

DCLee

Sounds like the Corsa is bad news. But there aren't any good solutions for the DOT street/track tire people. The MPSCs in 265/285 are fine at first, in my experience, but then harden into bricks after a 4-5 track days. Yeah, the wear is fabulous, but the rock-hard tires never get heat in them again.

The RA-1s, which I have been advised to try, have a 245 but no 285x18--I think 275 is the biggest 18-in. rear they currently make. Someone correct me if I'm wrong, and I'll rush out to buy a set.

That leaves two alternatives:
1) Suck it up and buy Hoosiers as a track-only tire. Short life, but a great tire.
2) Buy Pirelli slicks for the track as a second set--cheaper and *much* better than those unidirectional Corsa things.

Am I missing anything here?...

Lee in D.C. (back in Hoosierland)

Dennis K

Tracking on weekdays is always a gamble. I arrived at Laguna at around 12:30p due to work and ended up doing only the two afternoon sessions. Which makes the poor condition of the front tires even more galling - I've only put 7 heat cycles on them.

Maybe there was a defect in the compound for the batch of Corsas released to the USA through TireRack. Three different cars at Laguna and all having the same outside shoulder chunking issue? It's hard to imagine that Pirelli wouldn't see the same problem with even minimal testing.

CarreraGT - I'll let you know where I end up buying the RA-1's from. Let me know how you fare with TireRack.

JJayB

I bought the Corsa's so I could occasionally run them on the street between track days. I'm running 235 and 315 on 9 and 11s and full
tread depth. After two track days at Willow Springs several observations.
1. Corsa's felt better and were faster than the MPSC.
no sudden breakaway like MPSC.
2. Like others, I saw rubber chunking on the outside edge but it was only
the left side. Willow is extremely hard on left side due to high g loads
due to high speed sweepers.
We hired Cort Wagner to help in our set up and after several sessions the best lap times were with 31 and 33 psi hot. I'm running 1.2 neg and 1.5 rear.

I've got duel spring Eibachs with Bilstein custom valved shocks. He felt were were getting the max out of our set up and the only way to go faster was go mono ***** with race shocks (Motons).
The Corsa's are about 1.1 sec. slower than the best times I've run with Hoosiers. My $.02.

Carrera GT

Okeydoke, I'll try lower pressures today.

Carrera GT

Stranger than strange. I think the Corsa's just can't handle heat. They get hot. Real hot. Damn hot. Hot enough to boil a Monkey's bum.

Today, running 32 and 34 hot, the tyres didn't roll over on the shoulder (riddle me that!) and didn't chunk on the shoulders. They also had a little better directional feel and seemed to work better under brakes. Today was a relatively cool day. Ranging a 70, I'd guess. Maybe mid 60's. One thing I really liked was the control and feel under late-braking. One thing I didn't like was the lack of grip under acceleration.

I wouldn't be in any hurry to pay for these things again, but they're good in colder conditions.

viperbob

Funny, I don't see that reading on my Pyrometer

Cuppie

Try 32 hot and camber up to 2' 30" front and 2' 40-50" rear.

Mel

Anir

Carrera GT,

I've never run the newer Corsas, but have tracked the older P-Zero C's for two years on a 993TT (245/35-18 and 285/30-18). Ran them on the street all summer, and on hot track days. Started aiming for 38 psi hot, but gradually reduced this to around 32-34 psi hot.

I thought they offered great grip, which was consistent over several events and throughout the weekend. When originally running too high pressures, they did get a little slippery towards the end of a 25-30" run session. Never had problems with chunking, or premature / uneven wear.

Interesting to see that the newer Corsas have given people problems.

Dennis K

Thanks for the report. Very interesting.

Thinking about it now, all my track days on the Corsas have been on days where the ambient temperature was 90 deg. F and above. I guess that could be a reason why they chunked but I'm still puzzled by the readings I saw from the pyrometer. I never saw anything above 195 deg. even after 8 consecutive hot laps and checking while in the hot pits.

I'll be at Sears Pt. on Sunday and if it doesn't rain, I hope to see what these tires will do on a cool day.

Carrera GT

Dennis, if you were thinking Laguna was a little tough on sound on Monday, you might try Wednesdays (92 dB) but they were insanely strict. I was meat-balled for having the passenger window up (no passenger) and the guy giving the "wind the window down" signal was making a motion that looked more like "paint the floor" or "wax on, wax off" ... I'm not sure, but he certainly wasn't giving the window winder signal plus I'd run with the passenger window up all day, so I don't know why they suddenly decided to change the rules (open window beside each occupant as far as I know) half way through the afternoon. And other guys various griped that sound was hitting them on the same setup that passed the last time they ran a 90dB day. Laguna has gone to the soccer mums.
I wish the Crock family had put $200 million to buying up every whiner around Laguna instead of funding NPR. And for me, that's saying something.
I think I'll have to go to Radio Shack and buy a sound meter. I couldn't hear a "loud" car all day but they kept sending 'em in with readings over 92. I enjoy a good conspiracy theory as much as anyone, but there's something funny going on at Laguna because they were just plain wild on the flags yesterday.