Tire vibration / thumpping issue at track

[rob76turbo]

All,

Went and did a casual track day at MSR in Cresson, TX and very quickly noticed something developing on my Boxster S.

Running R888's and I felt a vibration and heard a thumping coming from the
right front tire. This only happened during right corners, when the right tire
in normally unloaded. During left had corners, there was no noise. I looked at
the tire itself and saw that the outside edge was down to slick and the inside
edge still has some of the grooves left. This got progressively worse as I ran
sessions, and to note, there was some tread at that outside edge at the
beginning of the day. I am wondering if the uneven tire wear was contributing
to the vibration / noise. Another PCA / Boxster guy happened to be there
and as I described the issue to him, he thought wheel bearing, but I am not
sure... Any thoughts?

[Bladecutter]

My '98 Boxster made the same noise in the right rear tire, and the cause for it was due to that strut having leaked out its oil, and eventually wore out.

Once I replaced the rear struts, the car no longer made that vibration thunking sound on hard right turns. Just like your car, it was silent on left turns.

I would take a look at the strut, and see if their is oil all over the body of the strut.
If there is, its time for new ones.

BC.

[Topless]

Lots of possibilities. Failing bearing, uneven tire wear, alignment problems, tire pickup, failed drop link or A-arm bushings, failed strut. You can check your bearing simply grabbing the tire and giving a yank left or right. You should not hear a clunk or feel any play in the wheel. Other suspension components are best checked on a lift where you can get a good look.

Brad Roberts is our local suspension Guru. He probably forgot more about Porsche suspension then I will ever know. Perhaps he will chime in.

[renzop]

Bad wheel bearing can be identified by pushing in hard on the tire at the top of the tire towards the center of the car. Use all your weight to do this. If the bearing is going bad you will feel a definite little click-click as you displace the outer bearing race.

[986FortyEight]

Different option: front engine mount.
I had the exact same problem at a PCA event at MSR and couldn't figure it out. everyone tried the car and identified the vibration to front right wheel. Not knowing was driving me insane! eventually got it on the lift at fifth Gear and saw immediately the front mount was toast. Replaced t and the vibration was gone. mystery solved.

Good luck, and let us know when you find the cause!

Mike

[rob76turbo]

I use Fifthgear too. Great folks. Can't wait to see their new facility.

I will take a look at the front motor mount when I have the car up on a lift.