Need help front end Vibration - on Track car

[ecm911]

Symptoms:
High speed (over 60 mph) under braking - Front end hoops and wheel vibrates with occasional slight pull to left. The vibration/hop is more pronounced as speed is increased.
Nothing on lower speed braking
Drives straight and no issue with no braking as well.

Car is SC t – dedicated rack car, suspension was replaced 3-4 years ago. Also Have brake cool ducts.
What I have done –
Replaced both front brake calipers with rebuilt ones (when the problem started – right front caliper was stuck).
Replaced right front rotor and wheel bearings including inner hub.
Kept the same brake pads in (Hawk blue). Did a break in procedure.

Just did a two day track event and the problem persists – but it is much less server.
But nonetheless I have to get this resolved.

So I inspected and pulled and pushed everything on the front end with nothing coming to light, other than the front rotors.
A wheel bearing have a very slight movement but seems like an acceptable level. Inspected all brake pads – wear seems even – however the outside pad on the right front appears to have lost some material in the center of the pad –
The right front rotor is warped (pad material I assume), left rotor is fine.

I fear it is still in the right front caliper and would probably go with a brand new one this time. Just want to make sure this is the problem.


Here is my plan of attack –

Replace both front rotors (just to eliminate any issues here).
Check wheel bearings – replace if needed (Both side were recently replaced) make sure they are tight.
Replace with new brake pads – I have a set of ferrodo. – break them in.
Replace front tires with newly balanced ones – need them anyway.
Take a test run and see if I can replicate the problem.
If I can replicate the problem immediately it still could be the caliper but I have a least eliminated the rotors and pads as a problem.

I know that I may not be able to replicate the problem until at the track when it all heats up etc. But at least it is worth a try and if I can replicate it, I keep investigating…

Suggestions or comments well.
Thanks all..
Earl

[ZOA NOM]

You didn't mention ball joints. Did you check them?

Also, with recently changed wheel bearings, I would double-check to be sure they were tightened down correctly. At track loads, the "slight" movement you felt can be exaggerated.

[Kemo]

subscribing...im looking forward to the results

[Rusty Heap]

You said you are going to replace the tires.......good place to start, any flat spots on them from hard braking too fast to hard into a corner?

[Garen]

I had a similar front end vibration, right after installing the WEVO camber king strut tops. It ended up being slightly loose monoball upper strut nuts. Mine had the same high speed only issue, with everything else checking out just fine.

[ecm911]

Thanks all.

Zoanas - Ball joints are 3 years old and look great.
I agree on the wheel bearings - I generally have to tighen a few times after I replace them to get them tight. Will make sure they are tighen when i chnage the rotors.
Love the vibration in your avatar!!!

Dave - sure do have flat spots after the last event.

Garen - good point . I installed monoballs with the new suspension. I will check them to see if they are torqued. thanks. How did you diagnose that - were able to get some movement in the struts or did you notive a loose bolts, etc.

Thanks again

[ecm911]

Garen,

You have it! I check the front strut nuts ( top of shock) and the left was slightly loose. I could move the washer. So, cranked up the air pump and impact both sides tighter.

I can not take it for a check run just yet, have to wait a few weeks.

But I am sure this is at least a factor in the porblem, if not the entire issue.

I am still changing the front rotors, brakes and tires - then figners crossed.

Thanks Garen - you saved my more frustation. Appreciate it!!

earl

[Garen]

No problem!

I just checked based on the fact that the monoball upgrade was the most recent variable since my last track day, and I felt that when installing the unit at home, I was unable to get much torque on the nuts due to the shocks spinning. This, even with securing the shock body as tight as I could.

Regards,