ZR1 Cup tires
 

As anyone run the new cup tires on the track? Just purchased a set and was wondering what tire (cold) pressures were used. On the stock tires I am running 28 lbs. The tires seem to stick better when they get hot.

I ran mine at 30 lbs cold.

I start at 28-30 cold and readjust to 38 hot.

I bet few people have actually read this...Make note of recommended pressures and alignment specs...

http://www.tirerack.com/tires/tirete...nd_Feeding.pdf

I think the reason people are complaining about poor wear is improper tire pressure and alignment. You really need to have your car aligned to max negative camber to get even wear on these tires and keep the air pressures lower. Otherwise you are going to destroy the outside of the tires. With the softer compound on the outside of these tires, they just won't take the abuse like the PS2 harder compound will. Once you get the the car dialed in, I think you will be impressed with the sport cups. I have 4 track days on mine and can still see the little oval dimples in the outer edge tread.

You can easily get 1.5-2.0 degrees of camber on all four wheels with factory eccentrics.

I've got -1.2 F, - 1.3 R and ran the recommended tire pressures from the pamphlet. I had excessive wear on the outside shoulders of all 4 tires. I guess I'll have to crank in more negative camber...but, how much is too much to ruin your street tires?

Camber doesn't wear street tires much, it's toe that does the most damage.

& isnider

What alignment specs are you running?

I left mine alone as I believe a lot of camber leads to more tramlining on the highway, where I drive a lot.

I'm running -2.0 on all four corners. My suggestion is get the most out the eccentrics the car will allow...every C6 is different from the factory

Tramlining is actually reduced...the the less flat the wheel sits on the road, the less it follows tractor trailer trenches in the highway.

If you track your car, the additional camber on the highway will never outweigh the gains in on track wear.

Ian

I am running zero toe front and rear by the way and high speed stability increased significantly from factory setup...

Anyone who tracks the car needs to find an alignment shop that is willing to take the time to get the car exact, not just within factory specs which is a wide range.

Ian

....and you won't grind your tires up on the street with a precision alignment.

I took 10 seconds off my lap time at VIR after the track alignment and installing the Sport Cup tires.

The car wandered so much above 150 mph with the factory alignment and now it is rock solid at 170 mph down the back straight, it instills unlimited confidence now...

The Sport Cups stick like glue and don't get greasy after 5-6 laps like the PS2's did. The only time I will run my PS2's in the future is cold temps 40-50 degrees, the Sport Cups are a recipe for hitting a tire wall or barrier when it's cold outside.

Ian

Good stuff, I'm sold!

I agree with Ian's points. I loved MPSCs for the track on my Z06, and the MPSC ZPs were mounted this week on a set of centennial wheels for NASA at Autobahn Joliet IL next weekend. The MPSCs do take a while to warm up; I usually did not drive all-out until I saw an increase of 2 PSI on the DIC, then they were great.

The info Ian included from Michelin through the Tire Rack is good stuff; it does not specifically state that the info applies for ZP rather than regular MPSCs but it can't be too different. I plan on using Michelin's advice re: shooting for 25 cold/32 hot in the front, 28 cold/36 hot rear. Many have opinions on this but Michelin probably has some experience on this one...:D

More camber is helpful at the track on any tire; my first set of PS2s went too quickly because of outer shoulder wear. The same went for my MPSCs on the Z06; this was better after a more aggressive alignment was done. I had a performance alignment done on my ZR1 at a good race shop last July. We went with Pfatdt's alignment suggestion for performance street use/track use on street tires for the PS2s but the alignment did not hold after several laps. I ended up getting Pfadt's camber kit installed which allows for rock-solid alignment and higher amounts of camber can be applied if desired.

I am currently at -1.7 front, -1.1 rear, toe close to zero. This is Aaron Pfadt's rec for a street car with race tires, track use (also a trusted source of handling and alignment info). I have been on these settings for almost a year and there is no significant inside wear on my PS2s, but definitely better wear on the PS2s for the second half of last track season. We'll see what happens this year on the MPSC ZPs, as these are just starting points.

I may end up getting a pyrometer to compare temps across the tire to optimize performance and wear. At over $2K/set every bit of help with optimizing wear is a good thing. A boost in performance and stability can't hurt, either!

Noel

Well, how did it go last weekend? Going to get my car aligned in the next week. Still thinking about where I want to go on the camber...

It's this coming weekend but it's supposed to be in the upper 30s to low 50s so I'm debating whether to leave the PS2s on... 5/7 is the next event. I'll post with results.

Thanks, yeah please report back. I found Pfadt rec's that you were talking about:

Performance Street - Track Use with Race Tires

Front min max
Camber (deg) -1.6 -1.8
Caster (deg) 7.5 8.5
Total Toe -1/16" (0.17°) 0 (0°)

Rear
Camber (deg) -0.9 -1.1
Total Toe -1/8" (0.33°) -1/16" (0.17°)

Notes:
These settings will provide great track performance. The tires will wear the inside edges in street use, and the car may tend to grab the lanes of the road. Race tires will wear well at the track and provide high levels of grip. This alignment is compromised towards track use.

With those temps and Cup Tires you better do a couple warm up laps at 50%!

I would probably run the PS2's to be honest...not worth the risk IMHO.

I ran the Cup Tires at VIR in February and it just was too scary for me in the mornings slipping and sliding around. I got the car sideways a couple times and almost got hit by the car behind me.

Everyone wants to try and keep up with the ZR1's on the track and they don't seem to understand if you aren't hauling a$$ the first lap out and it was just plain dangerous in that regard.

Ian

I would get as much camber as I could. The fact is that the inside of the tire has harder compound and will hold up just fine. The outer outer of the tire softer compound (where there is virtually no tread) is the part you have to protect with the negative camber. I would go -2.0 without hesitation specifically with the Sport Cups.

Ian

Oh I have literally destroyed two sets of the front left and right lower air valance deflectors now that the car is sticking so hard in the corners.

I wish I could turn up the MRC a notch to a slightly firmer setting quite frankly. We need TOUR, SPORT and a third mode STIFF

Ian