Vibration While Braking After New Pads & Rotors

[gimpgutter]

I just completed the replacement of the front rotors and pads on my 2013 S6 with Disc Italia pads and rotors. Overall, the process wasn't horrible once you learn the little tricks to get the new pads in.

The good news: the brakes are finally quiet. Zero squeal when stopping.
The bad news: I now have a vibration / pulsing when stopping, noticeable in the brake pedal feel. It occurs with moderate to hard braking and is quite substantial. Braking seems strong, however.

I did everything by the book and followed this guide: https://www.audiworld.com/forums/s6-...6-7-a-2889241/

Some thoughts:

1. I cleaned every mating surface thorough with a wire brush and brake cleaner.
2. I lubricated the pins that hold the pads in place.
3. I applied anti-squeal compound between the back of the new pads and the new circular shims. I'm wondering if its possibly this, but the vibration only seems prominent on the front left wheel. I applied the compound to both sides. I simply didn't want to risk squeal after a couple thousand miles again.
4. I performed a proper bedding process. 30-0 mph stops, then 60-0 mph stops, then some light driving.
5. Wheels were not changed in any way. I put the same wheels back on the same hub. Didn't appear to lose any weights.
6. I put on new caliper hardware and torqued to proper spec.
7. I checked the rotors for any deposits, but they seemed fine. Also didn't notice any warping.

Any input, guys? I'm eager to get this issue resolved and get my car back on the road by tomorrow.

[bonafyd]

The rotors are probably not true/ perfectly round.. i’d go over the job again maybe something is loose who knows.
If nothing is loose then it’s more than likely it’s the left rotor or both of them. maybe a local shop can check to see if they’re true or not.
Hopefully you’ll get it sorted.

[goliath1]

You can get a cheap runout gauge to see if the rotors are out of round. Or try and rebed. You did everything correctly. This happened to me and a rebed fixed it..0-60 and back to 5 or 10 mph 5 times with 5 mile cool down. Biggest problem was finding a spot to do the rebed.
Good luck.

[db12]

During the bed in process did you notice the vibration?

[jinetics]

How is your steering wheel under braking? Any shaking? Did you clean the brake rotors with the brake cleaner? (the friction surface) Through a visual check, do you see any dark spots on the rotor face?

Sounds to be it's more like a suspension issue if everything checks out. Under load, your control arms flex, but once it flexes too much, it "bounces" back in a sense. I am currently going through the same thing (no pad or rotor change) but with new stainless lines.

[bpd]

Think rear brakes need to be done?

[gimpgutter]

The vibration started the first time I braked in the bedding process.

I did clean everything quite thoroughly with brake cleaner. Didn't notice any unusual wear pattern or deposits on the rotors.

I think the backs were fine.

[gimpgutter]

Forgot to add, the vibration is only in the pedal. None in the steering wheel during braking or normal driving.

[jinetics]

Forgot to add, the vibration is only in the pedal. None in the steering wheel during braking or normal driving.

Your rears are definitely the culprit if it's just your pedals. I would change your rear rotors and pads out as this is a clear indicator of warped rear rotors.

[gimpgutter]

Update:

I had my mechanic check it out today. He is confident it's a manufacturing defect in the rotor, a so-called "hard spot". He thinks during the tempering process, something didn't get heated properly, resulting in different material properties in parts of the rotor. Nothing is detectable visibly or with with a run-out gauge, but he was adamant it must be the rotors.

He didn't think that this would cause any premature wear on the pads and said it shouldn't get any worse over time. I still want to replace it, since it's not particularly hard to do and the pulsing is even more annoying than the squealing.

I guess I'll be reaching out to Disc Italia / Brakeworld for a new rotor.

[goliath1]

If you still have old rotors try swapping one at a time to isolate..