JPS

Started picking up a pretty bad shake at 85 mph + at the track. Coincidentally grease started melting and coming out the center of the axle on my 993. Thought it was a wheel bearing.

Mechanic said to put in high temp grease but that the wobble was a busted steel band in the Nitto.

Is there an easy way to confirm the theory and if so, how to find which wheel? Something that doesn't involve 90 mph on public roads?

931guru

Jack up wheels, one at a time, and slowly rotate tire, watching the gap between the tire and the ground (or another fixed point).

The tire with the broken belt will have a different gap at the point where it is broken.

It will also tend to be out of balance.

mark kibort

ive never heard of this... you would think that the tire would be out of round too, if this was even possible.
more than likely, just out of balance, as you might have shed one of the balancing weights on the inner rim area....
however, jacking the car up is a good idea. i would actually run the car in gear with the rear of the car on jack stands if this is a rear wheel .... or even mount the front on the rear for this test. spin it up fast and see if you hear or see a vibration

Bill Verburg

have the cv joints repacked w/ Neo Syn HP Calcium grease or Crytox, I used Neo and haven't had the issue since.


I've seen broken belts on trailer tires, It looks like a knot or twisted distortion in the tread, pretty obvious when you know what to look for.

996FLT6

If u have a 2nd set of rims/tires put them on and see if it wobbles at 85+ mph. If not it's the tire or the rim or both. I would try to rule out there is no flatspotting or tires that rotated around the rim which would affect the balance. Also visually check the rim for nething bent or out of round. Mike

Frank 993 C4S

Taken them off and have them rebalanced? You'll find out pretty quickly if it just some lost wheel weights.

ProCoach

If a belt has broken, it'll be clear when the respective wheel and tire is up off the ground and can be rotated on the axle or on a balancer. The distortion will generally be at the intersection of the sidewall and the tread. When you turn the wheel and look closely (or better yet, run your hands over the tread or rotate the tire with your hand stationary just above the tread), it'll be a pronounced lump or big, smooth blister.

It's more common than you might think.

JPS

Shop just called. Busted steel belt. Trying to figure out if it was the new tire or old one now.

mark kibort

That's good you got the answer.. hard to believe, but heck, anything is possible. wonder if that vibration was what was pounding the rear axle grease out the seal.

JPS

The grease seems to have melted. Street spec. Replacing it with track spec stuff. Vibration was prob 3 laps as I tried to diagnose what was going on.

mark kibort

glad it was a tire. wheel bearing grease is always a challenge . i tried the redline synthetic stuff once and at the track, became liquefied and ran out the seal cover. back to the litium based heavy duty high temp grease you get at local auto stores. seems to work ok

JPS

May be a tread splice issue. Trying to figure out admin traveling and not near the car.

Greg Phillips

This is what my tire (Hoosier) looked like with a broken belt.
This type of stagger does not work

Greg

mark kibort

thats an ugly tire right there!