warped brake rotors

[Screamer]

During my third hpde my car started develop a pretty good shudder under braking. Now on the street when the brakes warm up it has a noticable shake.
Anybody else experience this?
I'm aware the rotors should not be turned.

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[cosmo]

Could also be the pads, shuddering can happen as a result of glazed brake pads.

 

[JonS]

During my third hpde my car started develop a pretty good shudder under braking. Now on the street when the brakes warm up it has a noticable shake.
Anybody else experience this?
I'm aware the rotors should not be turned.

This is too late to help if what you have are warped rotors, but for the future, I used to tell students when i was instructing to stay off the brakes (or use them very lightly) the last lap, to let things cool down.

I don't know the configuration of the emergency brake on this car (still waiting for mine) but I used to avoid putting on the emergency brake after driving as well - I generally don't use that at all anyway.

 

[Zombo]

This was a hot topic of discussion about 15 years ago; I'm sure you can find a lot info out there. Stoptech did a lengthy white paper about it. Basically, it's been argued that there is no such thing as warped rotors. The pulsing you feel is due to brake pad deposits infiltrating the crystal structure of the rotor causing random hard spots which generates the pulsing. Sorry I don't have a recommendation, other than using track pads in the future and properly bedding them in. But I gave up this stuff 10 years ago.

 

[Zombo]

I believe the parking brake is a drum brake acting on the inside of the rear aluminum rotor hat.

 

[xt6wagon]

This was a hot topic of discussion about 15 years ago; I'm sure you can find a lot info out there. Stoptech did a lengthy white paper about it. Basically, it's been argued that there is no such thing as warped rotors. The pulsing you feel is due to brake pad deposits infiltrating the crystal structure of the rotor causing random hard spots which generates the pulsing. Sorry I don't have a recommendation, other than using track pads in the future and properly bedding them in. But I gave up this stuff 10 years ago.

guy at stoptech is a flaming idiot. You most certainly can warp rotors on a car. That said, properly designed brakes as he exclusively deals with in race cars don't. That isn't what he claims though. He ignores the fact that many cheap (and older) cars have front rotors designed around cost and packaging with out thought to what shape they change to when they go from 60F to 600F.

In this case I'm going with either an issue with pad deposits or damage to the system. I'm saying this as the GT350 does have properly designed rotors. If it had rotors from a cheap family car I might question the actual shape.

 

[NipSC4328]

Lol, don't know if I'd go as far as "flaming idiot", but I've checked rotors with a dial indicator and they can definitely warp.

 

[FTD]

I believe the parking brake is a drum brake acting on the inside of the rear aluminum rotor hat.

It is.

 

[jasonstang]

Did you park the car when the brakes are hot?
Normally just extra material being transferred onto the rotor causing high and low spots.

 

[snaproll]

Your rotors aren't warped. Go put some serious heat into them and they may recover if you haven't driven it too much. If not, you may find them worn unevenly and are junk but it won't be because they are warped. Using some crappy ceramic pad at the track gave my old car the shudders but a pad swap and a couple hard laps fixed it.

There's nothing wrong with turning them if you want. We race on rotors with the groove worn out so what's the difference? A quick clean of the surface by "turning" may also fix it, but may not.

I watch some clown try to use a dial indicator on a slotted/drilled rotor the other day at the track. Good luck with that. It doesn't work.

Agreed with above - If you use your brakes in the pits with the car not moving and hot brakes or use the e brake, you can cause a pad material transfer problem and feel it in the pedal. I even push he car around sometimes if I brought it in smoking hot. If I don't, rotors seem to have a higher likelyhood of going "tink" and cracking edge to edge.

What pads did you have? Which end of the car? Could you have held hot brakes while parked? How much meat is left - can you economically have some material taken off to try it?

 

[NipSC4328]

Your rotors aren't warped. Go put some serious heat into them and they may recover if you haven't driven it too much. If not, you may find them worn unevenly and are junk but it won't be because they are warped. Using some crappy ceramic pad at the track gave my old car the shudders but a pad swap and a couple hard laps fixed it.

There's nothing wrong with turning them if you want. We race on rotors with the groove worn out so what's the difference? A quick clean of the surface by "turning" may also fix it, but may not.

I watch some clown try to use a dial indicator on a slotted/drilled rotor the other day at the track. Good luck with that. It doesn't work.

Agreed with above - If you use your brakes in the pits with the car not moving and hot brakes or use the e brake, you can cause a pad material transfer problem and feel it in the pedal. I even push he car around sometimes if I brought it in smoking hot. If I don't, rotors seem to have a higher likelyhood of going "tink" and cracking edge to edge.

What pads did you have? Which end of the car? Could you have held hot brakes while parked? How much meat is left - can you economically have some material taken off to try it?

I agree, his rotors probable aren't warped, I was only commenting that it can happen, it's not totally unheard of. FWIW, the rotors I've checked were not drilled or slotted but were truck rotors, Ford Excursion for one and I had them chucked in a lathe, not on the vehicle. I've managed a CNC machine shop and foundry for 40 years as well as spending quite a few years restoring antique cars, Hudson, Essex, and Terraplane ... yeah, I'm somewhat of an old fart, but I think I can handle using a dial indicator. :cheers:

 

[JonS]

Just to add to this a bit. Someone mentioned good brake pads. I may be a bit out of date but track pads can really help here in terms of avoiding brake problems (on and off the track). The trade off generally is more noise which does not matter on the track, but can be annoying on the street and many do not perform well until up to temp.

 

[snaproll]

I agree, his rotors probable aren't warped, I was only commenting that it can happen, it's not totally unheard of. FWIW, the rotors I've checked were not drilled or slotted but were truck rotors, Ford Excursion for one and I had them chucked in a lathe, not on the vehicle. I've managed a CNC machine shop and foundry for 40 years as well as spending quite a few years restoring antique cars, Hudson, Essex, and Terraplane ... yeah, I'm somewhat of an old fart, but I think I can handle using a dial indicator. :cheers:

Fair enough and certainly not commenting on your experience or expertise. Just saying that the usual culprits to "warping" are of result of issues like pad interface problems (uneven deposits or whatever you want to call it), bad bearings, uneven mounting, etc which cause "warping." Since I quit using the cheapest pads I could buy for track days I haven't had a shudder that didn't clear up with some heat in 10 years of driving on the track.

 

[mattlqx]

Have you checked your lug nuts?

 

[NipSC4328]

Fair enough and certainly not commenting on your experience or expertise. Just saying that the usual culprits to "warping" are of result of issues like pad interface problems (uneven deposits or whatever you want to call it), bad bearings, uneven mounting, etc which cause "warping." Since I quit using the cheapest pads I could buy for track days I haven't had a shudder that didn't clear up with some heat in 10 years of driving on the track.

Agreed 100%

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