I recently drove my car to a weekend DE, 3 hour drive on street wheels-speed ranges from 0-100mph. No problems noted.

Upon putting track wheels/tires on and within first session, noticeable vibration similar to out of balance. The vibration varied, sometimes would start right away even at slow speeds, always getting worse at higher speeds. In some cases I could drive 1+ laps before vibration started, so I assumed it was tire balance and the warm up. Telling myself I had lost a wheel weight, I finished most of the DE before calling it quits and traded back to my street wheels. The issue was to the very limit of what I could accept on-track, looking back, I probably should have stopped, but it never really got worse.

3 hour drive home, no excess vibration except for one 5 minute instance where I got heavy rain, about in the middle of the trip, and during that time the vibration got so bad I thought I thought that I was going to have to pull over. Then the vibration went away again for 1+ hours.

Drove street wheels around town on/off next few days, some vibration but nothing bad. Put track wheels back on, vibration was worse than street tires, but not at bad as it had been on the track.

Street wheels back on this last weekend, more vibration again, clearly starts right at 70mph, continues well through 100mph+, I can feel it in the steering. Vibration is the same under accel or not, no change with clutch depressed.

I did the window weld trans mount and added semi-solid motor mounts both a few weeks prior to the DE event and test drove after each installation with only the slight extra NVH expected with each change.

I will be digging in this week to find the issue, just wondering if there are any suggestions. I personally doubt the recent mods could be the culprit, perhaps a loose front steering or suspension component? Thanks for any suggestions.

 

Spin up your wheels and check to make sure you don't have a bent wheel. If not, then your wheels/tires are out of balance. It's very common for tires to rotate on the rim causing them to go out of balance. Mark the position of the tire relative to the valve stem and keep and eye on it. I used to glue my tires to the wheel with 3M adhesive which greatly reduced it. If you see them moving on the rim, then flip the wheels from side to side on the car every few sessions.

 

Yeah thanks for the suggestion, I hope it is as easy as a wheel out of balance.

My point with the long winded description is that this problem seems to be a bit intermitten and also started all at once on both sets of wheels/tires.

If the problem was only with the track wheels and completely went away when I re-installed the street wheels I would be sure it is a bent or balance issue only with the track set.

Could be coincidental that both sets have started to go out of balance at once....

 

If the vibration became bad enough on the street tires that you were tempted to pull over I'd be checking the suspension bushings over real closely! Does the shake come through the wheel? Seems like something maybe exacerbated by having put on stickier tires perhaps? Get it in the air and tug on everything and poke at it, I'm not convinced its balance if the issue continued after swapping wheels like that...

 

Thanks again, I will check everything and also freshly rebalance one set and recheck.

I will report my findings...

I can feel it through the wheel, but it somehow doesn't feel as direct as when it is a wheel out of balance.

Dave

 

I finally got my track set re-balanced and that seems to have taken care of the issue. I must have lost a wheel weight between track events somehow.

I did check the car thoroughly and one front rotor retaining screw set was a bit loose. This was a possible contributor but I would expect torquing the wheel on should have tightened the rotor up sufficiently.

Just posting in case anyone else runs into this. I've never had an out of balance condition like this, it varied from run to run, sometimes did not vibrate much until after a couple of laps, sometimes bad at 30 mph, sometimes not noticable until 70 mph. I use the foil tape over the weights, so not sure how I lost a weight without noticing.

I guess my street wheels have just enough wear at the same time to exhibit some out of balance vibration at the same timeframe.