@VIR Trying to Diagnose a Clunk

[eacmen]

At the track this weekend. Noticing a clunk from the right rear wheel. Only hear it when coming into paddock from a hot track.

Jacked up car, control arms seem tight. Sway bar seems tight. No play in the wheel.

If you jack up that corner of the car an inch you can hear it on the way up and down.

Any ideas?

[Casa de Mesa]

No oil from the strut leaking anywhere? Almost sounds like a bad strut if no suspension is obviously loose. What about the lock rings on whatever coilovers setup you are running? Caster/camber plates?

If you can hear it while jacking, get someone to help isolate it. Have a stethoscope? That can help tremendously if so.

[AXDB]

Check the through bolt in the lower control arm. The bracket that holds the lca into the body pocket.

[eacmen]

All good suggestions. Checked major suspension components and all seem okay.

Recorded a video with the noise. Only happens when the car is hot after pitting in.

https://youtu.be/NMouztElHyY

Sway bar end link? They are the GC ones.

[Casa de Mesa]

Sounds like a spring perch to me.

[Casa de Mesa]

Are your coilover lock rings tight?

Edit: also just reread 1st your post. It's the rear, not front. Still sounds like like a spring perch to me

[Estoril]

Pull the wheel and then cause the noise with the jack. Possible spring binding on the spring perch.

[eacmen]

Sounds like a spring perch to me.

The coil springs are usually loose. using GC weight jacks with linear springs that aren’t very tall. I didn’t think raising the car so little would disengage the spring.

[Casa de Mesa]

The coil springs are usually loose. using GC weight jacks with linear springs that aren’t very tall. I didn’t think raising the car so little would disengage the spring.

Agree with Estoril

You might be able to get a visual on the spring moving with a flashlight and the wheel still on. I have a racecar on coilovers (not an M3) and it does this when you jack it. My bet is the bottom of the spring is dancing around when you load and unload. If it's doing it while weighted and pulling into pits, could be something wrong with the spring perch. Or loose.

Sorry if I'm steering you the wrong way, but sounds like a spring to me in that vid

[eacmen]

Made the decision to keep going out in each session as I didn’t see any immediate safety issue. Last session went out and on the 4th lap was going down the back straight and the rear end came loose for no reason. Slowed down pitted in and drove the car right into trailer and drove home.

Will put it in the air soon to investigate.

[AXDB]

All good suggestions. Checked major suspension components and all seem okay.

Recorded a video with the noise. Only happens when the car is hot after pitting in.

https://youtu.be/NMouztElHyY

Sway bar end link? They are the GC ones.

The only way to check the RTAB is to pull the bracket out did you?

[eacmen]

The only way to check the RTAB is to pull the bracket out did you?

I did not.

[AXDB]

I did not.

Only reason I ask is because I had the exact same failure that was doing the exact same thing at Road America. The only way that I was able to diagnose it was to get the car in the air and then you can move the actual lower control arm in the RTAB pocket which led me to see that the bolt that compresses the bracket on to the actual bushing itself was loose

[eacmen]

Only reason I ask is because I had the exact same failure that was doing the exact same thing at Road America. The only way that I was able to diagnose it was to get the car in the air and then you can move the actual lower control arm in the RTAB pocket which led me to see that the bolt that compresses the bracket on to the actual bushing itself was loose

Definitely appreciate the insight. I have not done RTABs before but know enough that I don’t want to do them myself! 😂

I had limited tools/time at the track. So I basically just put the rear end in the air and pulled on any major structural member and didnt feel anything loose.

Previous owner put the Fall Line RTABs in which I think are a solid bearing and not bushing.

But now that the season is over going to have plenty of time to figure this out.

[bigjae46]

Sounds like a loose bolt.

Not trying to be a dick but never a good idea to go on track with a suspension noise. Especially higher speed tracks like VIR.