Disk Warping Issues

[hetman]

Hi guys. I'm after a bit of input on your experience with warped disks, I can't seem to get a straight story out of any mechanics (though most are usually keen for a dollar). Any suggestions or recommendations for a mechanic that might be equipped to deal with this would be awesome.

I have an R33 GTS-t with the standard 4 pot calipers. Haven't had an opportunity to track it, so while there are some nice roads out of the city for spirited driving, obviously there's only so hard you can push it. Until recently I've probably braked pretty hard even in normal traffic because of annoying squeel from the fronts.

Originally my disk warping problems started with a set of slotted RDA's together with some PBR performance pads. Warped after a couple months. From then on these would hold on for maybe 2 weeks if machined, and then the shudder would slowly creep back. During this time I had a problem in the steering rack fixed which had a bit of play when warm, a wheel bearing and stub axle bearing replaced, all on the right side. Since then no one has been able to fault the suspension since I presume what remains is a brake heating issue.

Eventually I had the disks replaced with original Nissan rotors and pads downgraded to Bendix Heavy Duty. Of course, it didn't fix the problem. After a while these rotors started to go as well, the killing blow being a nice drive through some mountains... the disks badly warped as a result (in retrospect those Bendix pads probably weren't so good for those rotors... there didn't seem to be any fade when hot).

Anyway, no amount of machining seems to get these disks good now. At best it reduces the shudder which then returns in full force over the next few days!! I've downgraded to a Maxi pad but that seems to make no difference (at least this guy managed to finally shut the squeel up with some shims & grease).

I understand cast iron disks if seriously stressed tend to result in patches hardening due to uneven carbon content so it's likely these disks are fubared now anyway. This is consistent with the uneven grabbing I get from the at low speeds (30km/h and below) which doesn't seem to be coming from the back given that's been recently worked on.

I presume if I upgrade to some DBA 5000 this might finally make my issues go away, but I'd like some advice before I pour more money into this.

Cheers

[MrStabby]

I have the same problem.. as yet unresolved. Not bad on the street but its a jackhammer on the track.

Make sure the mating surfaces between the rotor and the hub are completely clean - no rust or other gunk at all. Even a tiny spec here will cause shudder.

I cant see any point in you changing the rotors again - BTDT and it didnt help me.

[Abo Bob]

Are you bedding in the pads properly each time you machine the discs?

Have you checked that all the pistons in the calipers move freely in and out?

[Roy]

Remove the rotor and check the face colour of the rotor, is the inner different to the outer. Its possible that you have trailing pistons in your caliper meaning that there is always pad contact and in turn heat input. When you get up it and give it some stick the rotor distorts due to the uneven heat distribution.

But also, is it just simply a case of the use? I doubt it, but remember brakes like engines, gearobxes etc all like to be warmed up with a bit of heat put through them before you really get stuck into the braking.

When you say the rotors are warped is anybody actually checking the runout of the rotor? Is it both fronts, only rears, only one particular rotor....which rotor/s is warping?

[hetman]

I've bedded them my self on a few occasions (no stopping until cool again and all that), let the mechanic bed them other times, etc etc. Never seems to make a difference either way.

The calipers have been checked by a couple mechs who reckon pressure is even on all of them. The runout's been checked, although on the last two occasions the first time the runout was apparently within tolerance, and the second time it was not. Shudder seemed just as bad in both cases. And strangely the shuddering seems to randomly get better and worse (which if my damaged disk theory was true I would've attributed to the angular displacement between the two front wheels, i.e. how the carbon hardened blobs lign up... I know seriously stretching for any kind of explanation here).

Good question with which rotor is warping, I forgot to mention that last time I had it checked although I can only assume if it was only one they would've told me (or not).

It seems the last mechanic I had look at this decided he couldn't make any more money out of me and lost interest in actually troubleshooting this any further. That's why recommendations for someone with decent persistence and experience with this sort of thing would be great.

Cheers guys

[blind_elk]

Maybe a stupid question, but it's not the ABS working is it.

If you are warping disks at that rate, then you must be really nailing the brakes all the time.

Have you discussed it with the manufacturer (RDA)?

[Abo Bob]

You can't necessarily trust that people have done what they say they have so check the two things mentioned, by myself and Roy, yourself.

[hetman]

So I thought I'd do a bit of an update.

I've had this looked at by a vehicle inspection joint. They seem to have found the problem: runout on the axle flange (wheel flange? I thought there were no axles on the front). I've had the car for a few weeks now and had a chance to push it a bit and there has been no recurrance of the shudder.

You'd think 4 other mechanics would be able to figure this out :-/

Thanks again for the feedback!

Edited November 24, 2008 by hetman

[mystery_kid]

may i enquire as to what runout is ?

[hetman]

may i enquire as to what runout is ?

I believe it is the surface variation as an object rotates. So for example to check if you have warped disks you measure the runout, a lot of runout means warped disks and hence shuddering.