Aron214

Hello everyone,
I drive a 2017 c63 sedan. I have the standard breaks on my amg. Over the past six months I’ve had to replace my rotors three times due to vibration under braking at highway speeds roughly between 50-60 mph. Under city speeds no vibration occurs.

Over the past months I’ve noticed the car will misaligned to the right and soon after the vibration occurred and could be felt on the floor, brake peddle, and steering wheel.

when it first occurred I was driving my car without worry. I was downshifting whenever I could, to get the popping sounds (can’t blame me) my braking was late (in the city). Then the issue started happening again so I changed my driving style. I would baby the brakes and no more downshifts.

The dealer first said it fell into a criteria where my car qualified for warranty rotor replacement. Second time around blame was on my” driving style” and they replaced the right front rotor and both rear rotors. Third time the blamed it on faulty brakes but they couldn’t really figure it out (my car was in the shop for two weeks before concluding rotors all around. Now the fourth time they are blaming it on the right tire not having even tread with the left (2 months ago and got a flat and only replaced the front left and not both)

So I am now at a crossroads I believe there is something wrong with the car. The issue is very consistent after 2k miles rotors go bad. I’ve never tracked the car. I do travel 300 miles on the weekends. I don’t know if I have a bent arm or a brake duct cooling issue. My local Mercedes are kind of guessing at this point and I don’t know what else to do. They want me to keep buying rotors every 2k miles when the should last 20k + the car currently has 19k miles on it.

Help...

ezatnova

Likely one of two things. On these cars, overtightening a lug can warp the rotor (I assume you warped a rotor...never have heard of a warped caliper in my life). Other than that( and this is where my money is), is you have a bad wheel bearing. That play will quickly cause a rotor to warp from it shifting around under braking. Demand that the dealer pull the front wheels and hubs and inspect the bearings for play.

Aron214

I was so angry I didn’t even realize I had the whole part wrong! yes rotors is correct thank you for the advice I will relay that to the dealer and see if they find anything significant.

LessIsMore

Rotors themselves don't usually warp per se, it is usually actually pad deposits on the rotor surface that cause the vibration that people called "warping". How do you build-up pad deposits on the rotor surface quickly and often? By frequent heavy braking and coming to a stop with your foot resting on the break which is pressing the hot pad into the hot rotor surface. So I could see where they might blame driving style.

With that said you would have to be doing some ridiculously brake-heavy driving all the time to build up pad material ("warping") so often.

For a rotor to actually be warped, yes it would usually to be with really poor over tightening of the lugs. Also see where it could be the bad wheel bearing too. But that would be very surprising on a car with so few miles.

msd3075

One thing too that can cause brake rotors to warp is from washing your car while the rotors are still warm. You should wait 30 minutes to an hour after driving your car to wash it, even if the car was only driven a short distance. You eant to make sure the rotors have cooled off enough that the cold/cool water from the hose won't cause the warm metal to rapidly contract and ultimately warp the rotor.

LessIsMore

No I don't think so. If that was true, every single person would constantly have warped rotors from simply driving in the rain.

msd3075

Yes, it does happen. Having a solid, continuous stream of cold water hitting only a portion of the rotor is very different than a mist of rain water maybe getting inside the wheels.

LessIsMore

Link to it actually happening?

Driving in the rain soaks the rotors and pads completely, not a mist.

Scenario: If you were on the highway and braked down to a stop quickly, while it was pouring, the discs would be quite hot and completely covered with water. If the temps were below say 60 in the rain, the water would be colder than what usually comes out of your hose. Rotors survive this and worse just fine. The disc would have to be literally glowing to get concerned about ambient-temp water hitting them.

alexasa

iTrader: (1)

warped rotors is apparently a complete fallacy and does not happen from what i've heard.

Mojo31

https://www.brakeandfrontend.com/warped-rotors-myth/

msd3075

I can find links that say that'll warp. I can find links that say it won't. Neither proves anything. What does is a basic understanding of heat transfer and material science. BSME here. Had to take both classes, plus many applicable ones, way back when.

The two scenarios being discussed (rainwater hitting the rotor while driving, and hose water hitting the rotor when stopped) are two completely different heat transfer scenarios. One if a fine(r) mist of water being bounced around inside of a wheel while it's spinning at several hundred RPM and evenly distributing the water across the entire braking system. The other is a direct flow of water across only a portion of the rotor at a time.

With the highway scenario, the rotor is not coming into contact with a direct flow of water. Only droplets that somehow work their way either through the spinning spoke or somehow under the car and through the inside of the wheel. Compared to the rest of the car, the rotor sees very little water. Yes, it's enough to cover the rotor, but it is nowhere near enough to rapidly quench the rotor. But if you were to actually "cover the brakes in water" as you described, as in drive into high water or a deep puddle that submerges the rotor, then yes, you could very easily deform the rotors.

With the car wash scenario, you have a continuous stream of cold water being sprayed onto the rotor (both conductive and convective heat transfer). Not a mist. Not a few droplets every so often. A solid, continuous stream. Not only that, the stream isn't going to hit the entire rotor evenly like it would in the highway scenario. It'll hit only a portion of the rotor at a time, causing portions of the metal to quickly contract while other portions don't. This can and will cause permanent deformation of the material between those two parts of the rotor (hot portion, and cooling portion) that is enough of a tolerance difference to experience brake vibration.

Been there. Had it happen to me as a stupid kid. Learned my lesson. Won't do it again.

PD46AG

Can't say with total certainty, but I had an Audi S4 that got warped rotors twice (vibrated badly under braking) when I routinely washed my car when it was hot. I stopped doing that and never had that issue again with the S4 or other cars. I now only wash my car when it hasn't been driven for an hour or so. Not worth taking the risk to find out if the "warped rotor" myth is valid or not. YMMV

ygmn

some good reading:

https://ebcbrakes.com/articles/brake...ions-answered/
https://ebcbrakes.com/articles/brake...you-off-track/
https://www.powerstop.com/pulsing-vi...ake-pedal-dtv/
https://www.powerstop.com/what-cause...pulse-vibrate/
That one has one way to ruin rotors is to "form a high spot on the rotor is if you clamp down on the brake after a hot stop"

robster

Did you ever resolve this or find the cause? I am on 4 set of rotors in 10k KMs!

munis

I have this exact same issue as well but it happened after a trackday. Around 60mph if I lightly press the brakes, I get a noise similar to a failed wheel bearing on a car. And I already did the brakes bedding in process, but that did not work at all.

robster

Im considering just changing the wheel bearings as all the bushings and control arms look good - no major noise or any signals that they are bad but I cant live with constantly changing the brakes - be a shame to say goodbye to the car I love if I cant fix her :-(

crazy00c230k

Interesting, the w207 e550s used to have a similar issue with right front rotors. They use the same rotor as the non-s 205 C63 (and non-performance w204 C63) but with a different caliper. This is the first I've read about it happening on a C63. The non-s rotors are the same left to right, the right rotor is the one spinning "backward" in terms of the cooling vanes, I always assumed it was overheating and causing excessive pad deposits. I bought a set of racing brake 2 piece rotors for my 207 and never had a problem again, correct cooling vane orientation on both sides and also saved a bunch of unsprung weight. They are pricey, but way cheaper than replacing rotors damn near twice a year. Thankfully I haven't had any issues with my 205, been a little over a year, but haven't driven as much due to covid...so fingers crossed.

robster

Oh this would be awesome - which racing set did you put on your car, i think i will try this... Thanks for the post.

crazy00c230k

Looks like this is the one for non-s applications

https://racingbrake.com/2141

I'd double check with them just to be sure though.