I always mark the race tires right where the valve stem is so i don't have to look for the stem when i'm in a hurry.

We put a new set of tires on the 911 one week ago at Tunderhill and this weekend i noticed that the markings had moved several inches in relationship to the valve stem.
So i marked the stem location again with a small dot and sure enough, after the first run session, the tires had moved again by several inches.

This only seems to happen in the rear, i'm guessing under hard acceleration when the tires are cold (first session in the morning).

Is this something that needs to be addressed or should i not worry about it?
Andy

Im not a pro but I know that would not sit right with me .....maybe under inflated?Maybe dismount them and rough up the beeds on the wheels? maybe theres rubber built up on that beeds causeing slippage ??...I would say somethings not right ...JMO
Mike

I've seen it on drag cars. Most screw the tires to the rim. It will mess up your tire balance when it moves. On a race car I'd get it looked at. You don't want to throw a tire at high speeds because it's way out of balance.

That was my first thought too.....it would throw off the balance of the wheel/tire.

Andy,

It will change/throw off the balance--the bigger the movement, the greater the change . . . .

What did they use for a lubricant when they installed the new tires onto the rims? Some of the shops here had been using armor-all or other sil-based stuff that doesn't evaporate, and we'd see the tires rotate around the rim (usually on the front end--i guess due to FWD and braking forces).

Best,

Steve A-

Wow. You have too much horsepower.

Is this on your street car or just an autox car? If dedicated autox car, I wouldn't even bother balancing them, much less worry about the slipping.

What 911?
News???

Rich

I see two possible solutions to this problem, you need to unplug a couple of spark plug wires or use less lube.

Andy, you still running this car?

Click to view attachment

I'm guessing too much lube putting the tires on or the wrong type of lube.

You did just put the tires on. What was used? How much was used?

Toyo Spec 911 race car, GTS class with PRC, SP911 class with PCA.

No Street, no AX, just *big* track ... 3.0L with aftermarket FI. About ~270 HP at the rear wheels. 245 x 16 Toyo RA1 tires in the rear.
Andy

PS: I have no idea what lube or how much of it they used when they mounted the tires. I didn't stick around to watch them put them on, just picked 'em up later ...

Traitor.

Portland is one of my favorite tracks . ....I love that track

Andy,

I copied this from a Michelin Technical Bulletin:

LUBRICANT FOR MICHELIN TRUCK TIRES (Revised 15 MAY 2006):

"It is essential that only an approved tire mounting lubricant be used when mounting Michelin® Truck Tires. Vegetable oil soaps or animal oil soaps, in solution, are the preferred materials for use as bead lubricants. Never use antifreeze, gasoline, ether, silicones, or any petroleum based lubricants. Never dilute lubricants beyond that recommended by the manufacturer since this may have a harmful effect on the tire and wheel/rim.

The lubricant serves three purposes:
• Helps minimize the possibility of damage to the tire beads from the wheel or mounting tools.
• Helps ease the introduction of the tire onto the wheel/rim by lubricating all contacting surfaces.
• Assists in proper bead seating and helps to prevent eccentric mounting.

It is important that the tire lubricant be kept clean and free of dirt, sand, metal shavings or other hard particles.

Tubeless Tires: We recommend lubricating both beads on the tire and the entire wheel surface from flange to flange. The tire must be mounted and inflated before the lubricant dries. Avoid using excessive amounts of lubricants. (Puddling of the lubricant inside the tire is considered excessive.)"

I've had good luck using 3 or 4 oz of "Murphy's Oil Soap" in a quart (32oz) of warm water--and usually allow a day--or two--for everything to dry before putting any high braking/acceleration forces on the tires (as always, YMMV).

Hope this helps!

I like the color.