mikymu

To see if they move relative to the wheel. Apparently tires move easily on forge wheels due to it's smooth inner wheel surface. My wheel shake badly on the track after couple track events and my wheel balance is all off. I could not figure out why until I mark the tire position relative to the valve stem on my CCW wheel and the darn thing move by about 1-2 inches after two track sessions. Some race cars drill hole in their wheel and screw down the bead of the tire to prevent it from sliding ... I am not going to do that

Easy fix is to rotate your wheels from side to side let's say 1/2 way through your track event to even things out (if you don't have directional tires). I am going to give that a try to see if I can keep the wheel balance relatively intact.

mooty

some tires are more "out of balance" than others.
all my tires rotate on my rims from bbs to ccw.
but i have been VERY LUCKY, no vibration despite rubber rotating.

Targa Tim

I don't see how this rotational movement is upsetting a wheel's balance, it is not like the weight has changed. Please elaborate.

996FLT6

^no vibrations at track but heading back home.... Mike

Leigh2

This happens all the time to us and it's quite common to have to balance the wheels...especially the fronts after or during an event. We bought a portable bubble balancer to carry in the trailer with us. It works very well!
http://www.harborfreight.com/portabl...cer-39741.html

Nugget

This happens to me all the time with my Hoosiers mounted on O.Z. Alleggerita wheels if I'm not careful. The tires will spin several inches if I brake too heavily during my warm-up laps and it leads to wheel vibration. If I wait a few laps for the tires to warm up and build pressure it doesn't happen.

It took me several events before I figured out what was happening.

Carrera GT

The wheel itself is (nearly) perfectly balanced (the manufacturer theoretically adjusts for the valve.) The tire is rarely round or uniform in weight, so it's always out of balance. Once the tire is mounted on the wheel, weights are glued to the wheel to compensate for the imbalances of the tire. If the tire then slips around the wheel, its position relative to the balance weights will change and so the balance of the wheel and tire is lost.

Some race tires are very stiff in the bead and require liberal application of "tire soap" -- the lubricant used during the tire mounting process to allow the tire to slip over the rim of the wheel without damage to either tire or wheel. This soap then requires heat and time to dry out and allow the tire to grip the wheel. Once the tire is set on the bead and dry, it will not rotate. Some wildly powerful cars (eg. modified Turbos) can still rotate the tire around the wheel, but it's rare and requires unbridled abuse of the powertrain. Some tires are so sticky that, on the track, usually under brakes, there's enough traction between a DOT slick and the track surface that it can rotate incrementally tiny degrees which, over the course of a hard running day at the track, can see the tire inch around the wheel until the imbalance becomes discernible.

mikymu

Portable wheel balancer ... what a great idea!



Yes, took me couple months to figure out ...

Very well said Adam!

Serge944

Yup. I have the same issue. I just live with it.

malmasri

So how does this tool (the Buble balancer) that sems so simple work? do you still need to add weights? how much and where etc?

CRex

+1. Just a function of all the braking you do. I stick a lil orange dot on all four rubbers to mark the stem positions before an event. After a day's tracking I usually get ~30 degrees of rotation in the direction of braking (often more rotation in the front v back). Not enough to upset the car on track, but DEFINITELY noticeable on the way home once I take the car over 150mph...

Search around the Drivers Ed forum and there are people who talk about mounting tires with water / hairspray instead of your garden-variety lubricant to solve this problem. Some claim success, but hasn't worked for me so far.

911SLOW

I know it sounds gay but I won't visit the tyreshop unless I have a full bottle of L'Oreal Elnett hairspray it's a little more expensive than your average drugstore hairspray but i like it a lot.
Highly reccomended and stops turning of tyre with style. : )

John

mobonic

happens to me with slicks more than anything... so much that the steering wheels shutters violently... after 1-2 sessions i have to take front wheels off and have them rebalanced.

ir_fuel

I read once that the GT-R rims have a special profile on the inside to avoid the tyre slipping on the rim.

Leigh2

"So how does this tool (the Bubble balancer) that seems so simple work? do you still need to add weights? how much and where etc?"

The bubble balancer has to be on a flat surface and out of the wind (inside a trailer works well). You place the head on the stand then stabilize and use the 3 adjustment screws to center the bubble in the circle. Then you put the wheel on the head where it centers on the cone shape and again you stabilize the wheel so it doesn't move. The bubble goes off-center if the wheel is out of balance. You then place (stick on) weights on the outer wheel rim (one at a time) until the bubble is in the center of the circle. Mark the spot and dismount the wheel and stick on the weights somewhere they won't hit the caliper. Good idea usually to remove all the old weights first... Takes about 5 minutes to do each wheel and the stick on wheel weights are readily available. We keep a few can of brake-clean around to clean off the wheels so the weights stick better.. The top comes off and the base unscrews from the post so easy to store... Ours has been rattling around in the trailer for years and still works flawlessly....very cheap, simple and effective piece of equipment. The only "challenge" with its use is to keep the wheel still as they tend to wiggle endlessly; but you'll be an expert after your first set.