krazzz

I have a problem that so far has me stumped. I have had a minor vibration in the steering wheel when braking since I got the car. It is very minor so I chalked it up as slightly warped rotors and didn't worry about it. In the last 500 miles the the vibration suddenly changed and became more pronounced on the right side. It now has a chatter/clunking noise that goes along with the pulse. This noise becomes prominent when doing medium brake effort below 40 MPH down to about 15 MPH. Any faster or slower and the noise goes away and the vibration is minimal. With very firm or very light braking it doesn't do it either. There is no question that it is fully on the right side. I know that there are three possible options: 1. Rotors 2. Control arms/ball joints 3. Tie Rods. Like I said, originally I thought it was the rotors but because of how fast and distinctly the vibration and noise changed I am starting to rule that out. There was no change in driving habits or any excessively hard or prolonged braking. Upon visual inspection the control arms don't seem to have an excessive amount of play. There is also no clunking when going over bumps or turning. The outer tie rod seems to have normal play in it as well. I really can't see the inner tie rod because it is covered by the boot so that is still on the list. The upper control arms are starting to squeak and I can see some cracks forming on the bushing so I was thinking about swapping those out. While I am at it I may have the rotors turned. That would at least eliminate half of the possibilities. What are your thoughts?

Fez2013

I would lean towards brake pads and rotors since it only does it during braking. Both could be unevenly worn or just warped.

MP4.2+6.0

I would go w/ brakes as most likely, but could be others too. And if brakes are not stock throughout, and especially if pads were changed mid rotor life to a fair number of ceramic flavors, the rotor may have end up with some deposits on it that can lead to shuttering and vibration. Not easily cleaned or removed by rebidding at times, and can take a pad change out and/or lift rotor machining to fix. If by any chance the rotors are non stock and especially if drilled, there are further weird potential issues there I could describe more that are not the normal naysaying stuff about btert drilled rotors. OP didn't include any info on the OE or non OE nature of the existing pads and rotors that might help some.

Add to the list of possibles too a bad wheel bearing that is getting somewhat loose rather than the more typical noisemaker ones, and then causing you the vibration feedback when braking.

Oh yeah, and the old kick yourself if it ever happens...have you checked the super obvious and oft forgotten, are the lug nuts fully tightened and torqued to spec? Ever check them since you got the car? Long shots are also things like a weird tire internal defect that acts up only in certain circumstances. A tire rotation can isolate that kind of stuff, or bent wheels and such that could play into vibration scenarios at times, though less likely to be isolated to just braking scenarios.

krazzz

Update
Thanks for all the input. The tires and rims (snow tires) only have a couple thousand miles on them and the minor shimmy was there before I put them on. Lugnuts have been re-checked. Wheel bearing is good.

I took another look at it this morning and from a different angle I was able to see it bit of a fresh rub mark from the upper control arm (rear position) on the chassis mounting point. Looks like I may have found the culprit along with possible rotor warpage. I was planning on replacing the bushings this summer anyway so it looks like that just got moved up to this weekend.

Here is my plan of attack:

New bushings - probably PowerFlex - I am aware of the stiffer ride and squeaks and can live with both.

Turn Rotors - they appear to be OEM

New Pads - RedStuff??? These seem to be popular on this forum. I have had good luck with them on SUVs in the past.

Thoughts? Thanks again for the advice.

MP4.2+6.0

All makes sense.

RedStuff are what are on my W12 now and commonly have been before. Going onto front of Mini S with JCW/Brembo brakes when they wear--OE JCW is a dust cloud--and likely will get to the RS5 Brembos already modded onto the Q5 when the OE's I first fitted wear out.

Many years experience w Red Stuff. They have very similar feel to OE but always win on the dust side. But now that Audi has held the line on brake parts pricing while EBC has pretty obviously policed its dealers to (be forced to) hold the line on price, the pricing delta is pretty much gone or at times can be in favor of OE. Since they have the bedding compound on the pad face, they seem less likely than other ceramics to have deposit issues on rotors than others can (hence my earlier reply/question in that vein).

TSHong

I agree with everyone. The brakes are the main culprit but loose suspension ( bushings ) will accentuate the issue. Sounds like you are on the right trail.