C7 S6 Braking Vibrations

[ubba]

Good morning,

Haven't been on here in a while since upgrading from my Laser B5 S4 but hoping I can get some help with regards to my S6 Brake System. I drive between Boston and NYC and use higher than normal amount of braking through daily city traffic.

Long story short, I had replaced all the brakes and routers at about 80k miles at the VW/Audi dealership near me and within a week I noticed a vibration under normal braking decelerating from 45-35 mph. I took the service tech for a ride to show them the issue but they are claiming to have never seen this kind of thing before. Car DOES NOT throw any codes or ABS lights on the dash. We both agreed it feels like the abs is kicking on in an unusual manner. There's no vibration in the pedals or steering during.

Decelerating from higher speeds there are no issues, no vibrations, slows down fine, I can feel the brake bite as it should at high speeds ...until 45-35 mph. There's no shake decelerating from 25 to 0 mph also and stops sharply as it should. The vibration happens under light braking and heavy braking only during the decelerating ONLY from 45-35 mph. Peak vibration happens at 40 mph and goes away once the car is slower than 30 mph. Problem has worsened since and the braking feels more severe now.

If anyone here has seen, heard or know of any ideas or solutions as to what could be triggering the ABS, please advise. I would greatly appreciate it. Thanks

[09S5]

If you just had this done at the VW/Audi dealership and purchased the parts from the dealership.
Then you should have a warranty on the rotors and pads.
Maybe they sold you a warped rotor and didn't know it.

Have you checked your wheel weights?

I'm just guessing here.

But I would lean on the dealership since this happened after you visit them.

Just my 2 cents.

1 of the professional may chime in and ofter more solutions.
Good luck.


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[Optimus247]

Check and re torque wheel bolts ... with hand torque wrench with correct torque pattern ...

[Audibot]

Caliper and suspension torques would be the first thing I would check--one of my Allroads had a vibration under braking and it turned out to be some suspension bolts were not torqued. (They should not have messed with the suspension when doing the brake job).

Did they replace the anti-rattle clips too?
Are you using the LV brake fluid? (granted this should not make a different, as I've used both LV and non-LV with no discernible difference)

[phats7]

Same issue I had when they changed the rears. I only do city driving, so I decided to take it on the hwy a few times and bed the brakes in and problem was solved. I thought they had given me warped rotors at first.

[ubba]

I'm over 5000 miles in and that vibrations at only 35 mph is still present...

[09S5]

Four cheap money, get your wheels rotate and balance, and see if you have a bent wheel or wheel weights issues.


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[Botbasher]

I'm over 5000 miles in and that vibrations at only 35 mph is still present...

Stock rims or Aftermarket? Aftermarket with a hub-centric ring missing caused me no end of drama!!

Felt really stupid after finding it, but at least I wasn't alone in my oversite!

Cheers,

KS

[Audibellybutton]

if its only vibrating when you press the brakes its the rotors

[Audibot]

if its only vibrating when you press the brakes its the rotors

Or the caliper bolts are not sufficiently tightened

[Botbasher]

if its only vibrating when you press the brakes its the rotors

OR...... It's the trailing arm ball joint!

I have been chasing down a high speed braking wobble for months. Rotors... Pads... Finally got all the 120k bushings replaced (found an upper one loose), checked the joints , all "OK"... even did the center driveshaft carrier bearing. It's changed speed, but it's still there. Was even thinking of replacing struts!!

It feels like a shopping cart that is just on the verge of a death wobble when braking unless turning (hence bushings). Braking from triple digits to 80s it gets skippy and wanders. Under 80 or light braking, it seems OK.

Did a little ultra high speed spanking of a Charger the other night and it got really bad afterwards. Got under and noticed the pass trailing arm ball joint weeping grease. Seems like it is tight enough by hand and prybar, but when you give it dynamic loads... it's no bueno. It even started to clunk a bit the other day, which I thought was an aged sway bar based on previous inspections!

So new arms on the way... we'll see if that fixes it. Expect the unexpected... I thought I tested it well enough, but obviously I didn't!

Fingers crossed!

KS

[Audibot]

OR...... It's the trailing arm ball joint!

Actually funny you mention it. I was chasing down some high speed wobbles and brake judders on my Allroad. It was downright terrifying at 80 mph. When I finally got her on the lift to replace some suspension components, I found the front struts were not even torqued to the control arm. Definitely helped solve some of my issues.

Moral: check for loose or insufficiently torqued fasteners.