Charley Hoyt

I participated in a HPDE on the Roval at California speedway yesterday. I was experiencing a vibration at speeds over 135. For most of the day I thought that it was being caused by the high (30 - 40MPH) cross winds coming down the front straight into NASCAR turn 1. But, late int he day the winds finally quit....and I was still having the vibration. I looked at the tires and brakes, and checked for bearing play between sessions and everything seemed fine. I have not had a chance to dig into the car yet...Any suggestions?

To help with the diagnosis...My car is a stock '08 Z-51 convertible with Z06 body panels, wheels, and tires. Also I have a new set of Nitto Nt-05's on the front, and new DBA 4000 rotors. They have been on the car for about a week with no issues.

Thanks for the help,
Charley

yakisoba

Check your wheel weights, or for a bent rim? An out of balance wheel might not tell you at low speed, but when you get up there, you might notice.

Jason

If it comes and goes with the brake pedal, it's a cracked rotor. If not, it's probably slag on the tires or a missing wheel weight. The faster you go, the more you'll notice odd little things shaking and wonder if they are important as you approach that 150-30mph brake zone.

Happy thoughts.

Olitho

Hi Charlie:

Can you feel it through the steering wheel like it is coming from the front wheels or is it the rear?

For me, in order of what I think it would most likely be:

1. Bent wheel, take them off and throw them on a balancer to see if they are bent. An alternative is to try and spin them on the car, but they usually bend more on the inside then the outside.
2. It could be wheel weights...
3. Re-check those hubs. It can be more than just a bearing. I have cracked hubs around the flange where it connects to the center of the hub.
4. Cracked rotors, but those normally only feedback under braking. Sometimes you can feel them while just driving, too. ACS is a rotor cracking track.
5. Check your end links and make sure they are all tight.
6. Cording a tire. A corded patch will provide some feedback, but mainly while turning.
7. Torque tube or cracked clutch problems...? Does it feel like it is coming from the drive train?
8. Harmonic balancer on the front of the engine?

Oli

gkmccready

Along with looking for missing wheel weights, check if there's a big track turd stuck somewhere on the rim throwing it out of balance. Check the cheap stuff first. :-)

AU N EGL

Yup track turds will do it.

Lost wheel weights
stone or grit in the brake pad

alignment

cars rake

jaa1992

At roebling I had a vibration my first session on the out lap. As we picked up speed it got worse, Took pit road and back to the paddock.

Nothing broke, nothing bent, a whole mess of track turds though. Cleaned them up - next session back to normal.

gkmccready

How would these two cause a 135+mph vibration? versus instability?

Charley Hoyt

The vibration is coming through the steering wheel...so, it must be the front. In this picture you can definitely see that i picked up more then my share of tire turds....But, This still doesn't seem like enough to cause this much of a problem. I put my daily driving wheels/tires back on but have not driven it yet. I checked the suspension and everything looked alright. The one thing that was a little odd was that with one front tire jacked up I could move the tire a little bit when I rocked it side to side...but, not up and down. I don't know it this is normal...but I assume that it isn't. On Tuesday I will bring the wheels to the shop and check them for balance. I didn't go off the track, so I doubt the are bent...but, I will have that checked also.

Thanks for all of the help.

Charley

Wayne O

If you don't already it's a good idea to tape your wheel weights down with silver metallic (foil) HVAC tape. Take a small hammer and tap the sharp edges of the weights down a bit then apply enough tape to help keep the weights in-place.

Olitho

I should have had on that list two other important things to check that could cause this problem:

1. Loose lug nuts, especially on the front
2. A cracked wheel spoke

Hmmm... How do I know all these things....? :o


.

AU N EGL

unequal toe on the front wheels.


I use HVAC aluminum duct tape over the stick on wheel wts

Jason

tie-rod

2000BSME

this.

bobmoore2

I disagree. That definitely IS enough tire turds to cause a high speed vibration.

gkmccready

Also looks like there's adhesive where wheel weight *used* to be.

mdk

this happened to me last year, worn wheel bearing is what was causing my high speed vibration.

mcar00

How about the front tires rotating on the wheels so that they are no longer in balance? Happens to me all the time.

MNCrystalRed2011

If you are grabbing the wheel at 3 and 9 and it is has movement, then it is likely tie rods.