[smithf80]

I'm sure this is all in my head but nevertheless I want to ask.

Today on my way home from work someone stopped dead on the highway, I believe something flew off the car in front of him. Either way I went from 65-0 pretty damn quick, and yes, I did come to a complete stop. My car stopped just in time and all was fine, I did hear some tire squeal but other then that it wasn't much of a show. Brakes felt a little funny for the next few seconds and then went back to normal.

Now I'm in overly-anal-is-anything-messed-up mode. I don't think anything is wrong and I don't think the rotors are warped, its kind of hard to tell if theres any shaking in the wheel when braking because the wheel vibrates slightly anyway but it doesn't seem to exhibit any shaking (like my last car did when its rotors are warped). I think bmw performance school does hard braking exercises and I doubt they change rotors after every class lol.


TL;DR Basically, generally speaking, will a hard slam 65-0 brake cause any warping on the rotors?

[Pauleebe]

Rotors get hot when used heavily, due to either constant use and/or hard usage. Repeated usage when hot causes warping. Hot brakes also are less effective at slowing your car until they "cool off".

One emergency stop won't damage your rotors, but likely caused them to temporarily heat up in that instance. You may have burnt through your brake pads a little bit more quickly, but nothing the vehicle isn't designed for.

[smithf80]

Originally Posted by dwalls90

Rotors get hot when used heavily, due to either constant use and/or hard usage. Repeated usage when hot causes warping. Hot brakes also are less effective at slowing your car until they "cool off".

One emergency stop won't damage your rotors, but likely caused them to temporarily heat up in that instance. You may have burnt through your brake pads a little bit more quickly, but nothing the vehicle isn't designed for.

That's what I thought, my braking on the trip otherwise was not heavy so I'm sure they weren't overly hot before this.

I know constant stops like this can mess stuff up

[rking117]

it is possible but not likely. Like the previous poster said, they would have to be heated then cooled and reheated again fast. One way to do it is to brake hard on a dry day and then drive straight through a puddle of water. Instant warpage

[NO_RETURN]

If you were braking from 150 - 0 as hard as possible repeatedly until your rotors glowed like the sun...then you may have something to worry about.

[GAS428]

Originally Posted by smithe90

I'm sure this is all in my head but nevertheless I want to ask.

Today on my way home from work someone stopped dead on the highway, I believe something flew off the car in front of him. Either way I went from 65-0 pretty damn quick, and yes, I did come to a complete stop. My car stopped just in time and all was fine, I did hear some tire squeal but other then that it wasn't much of a show. Brakes felt a little funny for the next few seconds and then went back to normal.

Now I'm in overly-anal-is-anything-messed-up mode. I don't think anything is wrong and I don't think the rotors are warped, its kind of hard to tell if theres any shaking in the wheel when braking because the wheel vibrates slightly anyway but it doesn't seem to exhibit any shaking (like my last car did when its rotors are warped). I think bmw performance school does hard braking exercises and I doubt they change rotors after every class lol.


TL;DR Basically, generally speaking, will a hard slam 65-0 brake cause any warping on the rotors?

Here is the Science of Brake warping.

Metal when machined produces internal stresses. To stress relieve the steel, manufacturers will heat the metal to relieve the stresses allowing the metal to warp. The machinist then re-machine the metal to straighten it out with out the stresses. This allows the metal to get hot with out warping.

Cheap rotors will warp under hard braking because they do not stress relieve.

I am willing to bet dimes to dollars that BMW does stress relieve their rotors.

so why did your brakes feel funny after hard braking?

Two possibilities,

First the hard braking deposited some material on the rotor. some moderate braking will clean it off. This happened to my wife's Volvo.

Second is after you stopped did you stay stopped for while? if you did than you might have allowed the rest of the rotor to cool and the section between the disks stayed hot, this could cause a little warping. Again the moderate braking should resolve this effect.

Recommendation: After hard stopping, allow 1.5 car lengths in front of you. Than after you stop reduce brake pressure to allow the car to slowly creep forward. This allowed the rotor to cool more evenly as well as removing heat from the pads. And you will eliminate the thumpy feeling in your brake peddle.

[smithf80]

Originally Posted by GAS428

Here is the Science of Brake warping.

Metal when machined produces internal stresses. To stress relieve the steel, manufacturers will heat the metal to relieve the stresses allowing the metal to warp. The machinist then re-machine the metal to straighten it out with out the stresses. This allows the metal to get hot with out warping.

Cheap rotors will warp under hard braking because they do not stress relieve.

I am willing to bet dimes to dollars that BMW does stress relieve their rotors.

so why did your brakes feel funny after hard braking?

Two possibilities,

First the hard braking deposited some material on the rotor. some moderate braking will clean it off. This happened to my wife's Volvo.

Second is after you stopped did you stay stopped for while? if you did than you might have allowed the rest of the rotor to cool and the section between the disks stayed hot, this could cause a little warping. Again the moderate braking should resolve this effect.

Recommendation: After hard stopping, allow 1.5 car lengths in front of you. Than after you stop reduce brake pressure to allow the car to slowly creep forward. This allowed the rotor to cool more evenly as well as removing heat from the pads. And you will eliminate the thumpy feeling in your brake peddle.

Thank you for the extremely well written explanation.

You explained what I really wanted to know which is why the brakes were funny for a few seconds right after this. Both of the scenarios make sense, most likely the second, I tried to do some even 60-30 braking to clean off the rotors after and I think that did the trick. Either way car felt completely normal on the way to work and I have to say BMW's excellent brakes definitely saved me yesterday.

[crono06]

And this is also why after going for some laps, they advise that you do not put on your parking/e brake.

[dreamspeed]

if anything, check your tires to see if there are flat spots