Pulsating Brakes
#27
Junior Member
Join Date: Jan 2010
Location: Boston
Posts: 15
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'15 C300 4Matic
I have this with my car and told the dealer and they said it was just from the pads and to do a "hard stop" to even out the pads. Tried it but didn't help. Not sure if it wasn't hard enough. I only feel it during highway speed slow downs, not on local roads.
I guess I'll give it another shot before I bring it in for the 25k service. If not, going to complain again.
I guess I'll give it another shot before I bring it in for the 25k service. If not, going to complain again.
#28
Super Member
If you read them you obviously didn't really get what you were reading. Here's what's happening in your car washing example: Your pad & rotor get hot from repeated braking from driving. You go and park your car in the driveway and now the hot rotor and pad are now stopped and fixed in one position on the rotor. At this point the pad is essentially melting onto the rotor while you're stopped. As it cools (with
the cooling process sped up by the water), it essentially melts onto the rotor leaving a deposit (in the shape of a brake pad) and also creates a sort of binding to your rotor.
The next time you drive the car and hit the brakes as the rotor is spinning, you feel a pulsation every time the brake pad rolls over that part of the rotor with the pad deposit on it. The pulsation is NOT because of the rotors warping, its because of the brake pad deposit.
There are 3 basic ways to solve the problem: 1) get all new rotors, since new rotors have a uniform thickness 2) have your rotors "turned" which is basically a machining process that sands the entire rotor down to a uniform thickness (this removes that little bit of pad deposit in that one area). 3) Somehow get the pad to evenly deposit around the entire surface of the rotor.. This is a process that is similar to "bedding" the brake pads.
Here's what a pad imprint looks like.
Lastly, the sizzling action and steam is because the rotors are hotter than 100C (the boiling point of water) when you spray them. As soon as the water hits the hot rotor it turns into steam, and at the same time the metal contracts. Its the same thing that happens when you cook on a pan and run the pan under water immediately after.
the cooling process sped up by the water), it essentially melts onto the rotor leaving a deposit (in the shape of a brake pad) and also creates a sort of binding to your rotor.
The next time you drive the car and hit the brakes as the rotor is spinning, you feel a pulsation every time the brake pad rolls over that part of the rotor with the pad deposit on it. The pulsation is NOT because of the rotors warping, its because of the brake pad deposit.
There are 3 basic ways to solve the problem: 1) get all new rotors, since new rotors have a uniform thickness 2) have your rotors "turned" which is basically a machining process that sands the entire rotor down to a uniform thickness (this removes that little bit of pad deposit in that one area). 3) Somehow get the pad to evenly deposit around the entire surface of the rotor.. This is a process that is similar to "bedding" the brake pads.
Here's what a pad imprint looks like.
Lastly, the sizzling action and steam is because the rotors are hotter than 100C (the boiling point of water) when you spray them. As soon as the water hits the hot rotor it turns into steam, and at the same time the metal contracts. Its the same thing that happens when you cook on a pan and run the pan under water immediately after.
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Hapa88 (04-22-2017)
#29
Senior Member
The pulsating is especially bad on the highway for me right now. I know what I'm doing this afternoon. That new road to nowhere (upcoming business park) will be seeing me for a little while. Circles on either end too, so no stopping Hope that works... will report back tomorrow / when I remember to
#30
Senior Member
The pulsating is especially bad on the highway for me right now. I know what I'm doing this afternoon. That new road to nowhere (upcoming business park) will be seeing me for a little while. Circles on either end too, so no stopping Hope that works... will report back tomorrow / when I remember to
What was key for me? I have a 1/2 mile stretch of road with circles on either end and no traffic ... it's a new road for an upcoming office / commercial area, that no one really uses yet. Do this process as long as you can continue driving for a while without actually stopping. So... a stretch of road with circles on either end :-p
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Hapa88 (06-28-2017)
#31
Member
I forgot to update this, but the process in the powerstop link ( https://www.powerstop.com/what-causes-brake-pulsation/ ) worked
What was key for me? I have a 1/2 mile stretch of road with circles on either end and no traffic ... it's a new road for an upcoming office / commercial area, that no one really uses yet. Do this process as long as you can continue driving for a while without actually stopping. So... a stretch of road with circles on either end :-p
What was key for me? I have a 1/2 mile stretch of road with circles on either end and no traffic ... it's a new road for an upcoming office / commercial area, that no one really uses yet. Do this process as long as you can continue driving for a while without actually stopping. So... a stretch of road with circles on either end :-p
#33
Senior Member
Actually, I'm thinking it was the fact that I almost always park the car with Brake Hold. I've started just coming to a stop and using the park button on the car.. It's no where as elegant or nice as using the brake hold (come to a stop, push the brake one more time, press engine off, walk away) but I'm fairly certain that's why I had the resin build up.