joejoda

A friend of mine suggested I post a problem I am having with my 997 09 Turbo. I bought a set of stock rims from my dealer and I had them install a set of R6 Hoosiers on them. I ran them on the track two weeks ago, and everything was great until I hit approx 100 mphs. I started getting a vibration in the car. It got pretty strong the faster I got. Friend of mine thought it was wind buffeting, but we have changed wheels and ruled this out. The Dealer thinks it has something to do with the circumference of the tires which may be effecting the 4 wheel drive transmission. Anybody have a similar experience or have any ideas, I would appreciate suggestions. Thank

TT Gasman

Quite possible. What are the sizes of the Hoosiers in question? I know the sizes need to be kept relatively close to stock diameters to avoid issues.

joejoda

The fronts are p235/35 zr 19s
the rears are p295/30 zr 19s
The deal ordered and installed the tires. Any ideas?

sparkhill

The following list (in descending order of likelihood) covers the most common vibration issues:

1. tire imbalance
2. tire issue (flat spot, out of round)
3. wheel issue (bent, out of round)
4. improper wheel mounting
5. suspension issue

#1's-#3's are the most common. Try to locate a shop with one of these: http://www.gsp9700.com/

I run 235/295's in the winter without issue.

AAHTT

I used to run the same R6 sizes on my stock wheels and I have taken them over 160 with no issues or vibrations.

TT Surgeon

You may have lost some wheel weights at the track too (common), throwing it out of balance.

Hoosier_Daddy

Those sizes are fine ... 25.6 inch front and 26.1 inch rear diameter is well within tolerance will not to upset the all wheel drive ratio.

I echo TT - look at having lost a weight and then on to a bent wheel….

joejoda

Thanks for the feedback. The dealer is going to pick up the wheels and tires and have them re checked out for balance and any other issue. It is just unlikely that a car starts to vibrate at 105 mph. If it was out of balance you would feel the issue at a lower speed. If you had a bent wheel the road force balance would be out of balance. Before going to the track, tires and wheels completely checked out within normal levels.

RJFabCab

A couple of things to think about in addition to the other comments:

Gummy hoohoos can flat spot especially on a heavy car when sitting in the paddock after being run hard. This can lead to odd vibrations, but they usually subside after getting up to temp.

Road force balancing is all fine and good until the relationship of the tire on the wheel changes. It's no secret that hoohoos spin on rims... hence the shortage of Aquanet hairspray at Walgreen's nationwide. Mark your tires at the valve stems after they're mounted and see how much they spin after a weekend at the track.

Plus, it wouldn't be the first time that a bad batch of hoohoos was produced (out of round)...

TT Gasman

I had a wheel that vibrated like a mf after a tire change. Everybody thought the wheel was bent. The dealer tech remounted the tire and voilà back to normal. I'm still not sure what happened.

prg

Joejoda, did you use foil tape to secure your wheel weights?

Sticky tires + track use => really hot brakes => melted adhesive on wheel weights => flung off wheel weights => paint shaker like ride experience at speed.

ltc

Post of the week

joejoda

I did not use tape to secure weights. I did not see any missing weights when I removed the hoosiers and reinstalled my regular wheels. If you lose weights, you tend to see where the tape was holding the weights. If I did want to use tape, what kind do you use? Some tape does not hold up very well.

machina

I marked my kumhos to line up the tire and rim and i did rotate the tire on the rim.

Based on the direction of the rotation the tire rotated under acceleration and that is on my 997S so i bet your turbo with big torque is definitely spinning the tires on the rims.

This is actually a common problem. Try having a race shop mount the tires with hairspray as suggested in the previous thread. Make sure they clean the bead surface with some kind of solvent first.

joejoda

Follow up. The cause of my problems was tire rotation on the rim. My hoosiers spun on the rims anywhere from 6 to 10 inches causing the tires to be out of balance. I had them rebalanced and I marked the tires and the rims. The next time I ran on the track, I had the same thing happen again. How do you keep the Hoosiers from spinning on the rims?