replacing Rotors
10-06-2011, 09:19 PM
#1
Drifting
Thread Starter
replacing Rotors
I do a lot of HPDE driving with my 2000 Vette and am starting to get some very small cracks on the face of the rotor. They kind of look like small "spider web" type cracks. Not clear through the rotor, just onthe surface. Is it time to replace them?
10-06-2011, 11:18 PM
#3
Safety Car
Member Since: Nov 2000
Location: Shenandoah Valley Virginia
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My conservative rule of thumb on rotor replacement due to heat checking : I drag a finger nail across the worst spot. If crack is deap enough that nail catches it's time to replace. If the crack goes all the way to the outer edge of the rotor it's time to replace. A lot of folks run them longer, but I hate replacing a fully cracked rotor at the track.
10-07-2011, 09:57 AM
#5
Safety Car
The problem with waiting until they crack at the track, is they won't crack during a session. While they are cooling down, they crack, usually under the pads, and you won't notice until tun 1 of your next session, and then you are out that session. I go with the fingernail test.
10-07-2011, 12:16 PM
#6
Race Director
The problem with waiting until they crack at the track, is they won't crack during a session. While they are cooling down, they crack, usually under the pads, and you won't notice until tun 1 of your next session, and then you are out that session. I go with the fingernail test.
10-08-2011, 09:55 AM
#7
Drifting
The heat checks are not a big problem. They are your signal that replacement is just ahead for you. Keep a close eye on them, really get a good feel for how much they are checked. My problem is I know when to replace them, I just try and get "one more day", and that leads to cracked rotors at the track. Something I have sworn to do a better job of changing them next year.
Important note: heat checking means you had a good time the last time you went out!!
Important note: heat checking means you had a good time the last time you went out!!
10-08-2011, 10:32 AM
#8
Safety Car
My advice is to leave them until they fully crack.
As stated above, they almost always crack when they are cooling down.
I always let them cool and check them before the next session (leaving enough time to change them if possible-easily less than 10 minutes with practice.)
The thing about pro-actively changing them is that brand new ones sometimes crack right away, so you never know-the only thing you know is that all stock rotors WILL crack.
Tim
As stated above, they almost always crack when they are cooling down.
I always let them cool and check them before the next session (leaving enough time to change them if possible-easily less than 10 minutes with practice.)
The thing about pro-actively changing them is that brand new ones sometimes crack right away, so you never know-the only thing you know is that all stock rotors WILL crack.
Tim
10-08-2011, 10:37 AM
#9
Instructor
Member Since: Sep 2009
Location: Melbourne Florida
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Agree
I agree with leaving them on until they fully crack. But have a jack and a rescue rotor with you. Because it will happen during one of your track days and it is no fun having to abandon the event. And dangerous to get the car back home unless you tow it.
PeO.
PeO.
10-08-2011, 01:30 PM
#12
you can start doing a couple of things to "postpone" a real crack as long as possible.
1. make sure you get a cooldown lap where you use your brakes as little as possible. if you have to come in hot, drive circles around the paddock for a minute or two.
2. after you park the car, wait a couple of minutes, then push it a foot or two forward so the pads do not sit over the same spot on the rotor as they cool down. People run up to me all the time asking if I need help when I do that (thinking the car died). I just don't want to start the car to move it a foot forward!
the warning signs of being very close to the end will be heat checks growing taller (i.e. you can trace each line up and down for an inch or more) and being able to see them breaking up the outer edge (so you see a small "nick" if you are looking straight down on the rotor.
also, get in the habit of doing a moderate-to-hard brake application in a safe environment before the first real braking zone in your session - you do not want to be looking at 130mph on the HUD going into 60mph corner on cold tires when you hear "thunk thunk" of a cracked rotor for the first time. Also useful if you manage to put the pad wrong side in somehow or forgot to bleed boiled fluid, or close the bleeder etc etc...
1. make sure you get a cooldown lap where you use your brakes as little as possible. if you have to come in hot, drive circles around the paddock for a minute or two.
2. after you park the car, wait a couple of minutes, then push it a foot or two forward so the pads do not sit over the same spot on the rotor as they cool down. People run up to me all the time asking if I need help when I do that (thinking the car died). I just don't want to start the car to move it a foot forward!
the warning signs of being very close to the end will be heat checks growing taller (i.e. you can trace each line up and down for an inch or more) and being able to see them breaking up the outer edge (so you see a small "nick" if you are looking straight down on the rotor.
also, get in the habit of doing a moderate-to-hard brake application in a safe environment before the first real braking zone in your session - you do not want to be looking at 130mph on the HUD going into 60mph corner on cold tires when you hear "thunk thunk" of a cracked rotor for the first time. Also useful if you manage to put the pad wrong side in somehow or forgot to bleed boiled fluid, or close the bleeder etc etc...