Shimmy with light braking?

[gimpgutter]

My 2013 S6 recently started this issue where you get a very noticeable shimmy in the pedal and steering wheel at VERY low speeds when applying light pressure on the brake. It happens when just lightly applying the brake at less than 1 mph (slow creep at a stop light for example) and also when letting off the brake.

I have zero issues when braking at any other time. No other noticeable driving problems.

What could be causing this? Front pads and rotors are Disc Italia with probably 10k miles. Rears are stock and just checked out by my mechanic a few weeks ago.

Is it possibly a transmission or ABS issue? Carista showed no codes.

[3g_bishi]

%100 of the time when there is any kind of vibration when pushing the brake it’s usually almost always a rotor even if there new they can be defects or warped already, I would have the rotors checked again. Also check your tires for bubbles, wheels for bends, and make sure it’s not the engine that’s shaking and you feel it slowing down such as a misfire or bad motor mount. Good luck! How many miles do you have?


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[gimpgutter]

Thanks for the leads. Here are my thoughts:

1) I'm hesitant to blame the rotors, since I have zero vibration during other braking. I've had warped rotors before and they manifested themselves all the time. Still, I'll check it out.
2) I will check the tires and wheels out this weekend. They've recently been inspected and re-weighted, but it's not like I haven't hit potholes since then.
3) I was suspecting motor mounts, but this is something my mechanic just inspected a couple weeks ago. He found no leaking. I do get the following code on Carista, though: VAG fault code 01295. I don't have it in front of me, but I think this is the one related to communication with the motor mount harness. I've had the same code for months and the issue just came up.
4) Don't think it's misfire. There was no code and the car appears to be pulling as hard as ever.
5) I'm at 89K miles now....and stock turbos somehow.

%100 of the time when there is any kind of vibration when pushing the brake it’s usually almost always a rotor even if there new they can be defects or warped already, I would have the rotors checked again. Also check your tires for bubbles, wheels for bends, and make sure it’s not the engine that’s shaking and you feel it slowing down such as a misfire or bad motor mount. Good luck! How many miles do you have?


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[gta7]

%100 of the time when there is any kind of vibration when pushing the brake it’s usually almost always a rotor even if there new they can be defects or warped already, I would have the rotors checked again. Also check your tires for bubbles, wheels for bends, and make sure it’s not the engine that’s shaking and you feel it slowing down such as a misfire or bad motor mount. Good luck! How many miles do you have?


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I agree with all of this. On my old Charger, a heavy sedan. I had warped rotors a couple of times. Once less than 11.000 miles on them.

Heavy cars stopping fast it happens.

[wwhan]

You could try bedding in the brakes again, with a hard bed-in.

Background: Brake Tech: Brake Pad & Rotor Bed-In

"Failure to follow these procedures may result in brake judder, excessive noise, or other difficulties in bedding-in the new brake pads. The pads need a fresh surface to lay down an even transfer film. Residue from the previous pad compound on the surface or an irregular surface on a used rotor will cause the pads to grip-slip-grip-slip as they pass over the rotor surface under pressure. The resulting vibration will cause noise and telegraph vibrations through the suspension and steering wheel. This vibration is known as brake judder or brake shimmy. This is typically caused by an uneven transfer film on the rotor surface or an uneven surface on the rotor not allowing that transfer film to develop evenly. This is often misdiagnosed as a warped rotor."

Hard bedding of brakes: https://www.powerstop.com/brake-pad-break-in-procedure/ "Break in your PowerStop Brakes as follows:

5 moderate to aggressive stops from 40 mph down to 10 mph in rapid succession without letting the brakes cool and do not come to a complete stop. If you’re forced to stop, either shift into neutral or give room in front so you can allow the vehicle to roll slightly while waiting for the light. The rotors will be very hot and holding down the brake pedal will allow the pad to create an imprint on the rotor. This is where the judder can originate from.

Then do 5 mod*erate stops from 35 mph to 5 mph in rapid succession without letting the brakes cool. You should expect to smell some resin as the brakes get hot.

After this is complete, drive around for as long as possible without excessively heating the brakes and without coming to a complete stop (Try for about 5 minutes at moderate speed). This is the cooling stage. It allows the heated resin in the brake pads to cool and cure.

After the brakes have cooled to standard operating temperature, you may use the brakes normally."

[gimpgutter]

Well, I was going to dinner and got a transmission malfunction light and the following 3 codes on Carista: 17596, 17598, 17600. Guess it's the DSG. Hope this isn't too expensive to fix...