AP brakes pulsing, warped?

[gareth h]

I picked up a set of AP brakes off e bay (branded HSV), they have been fitted and I'm getting a pulsing through the brake peddle and a slight shaking of the steering wheel, unfortunately because they looked in such good condition I didn't check the discs for trueness before they were fitted.
When you use them hard the pulsing disappears and they work very well, is it likely they are warped? if so anybody know how much front discs are?
I've read about the transfer of pad material to the disc giving the same effect, if this was the case would it be obvious (the discs looked clean before they were fitted).
Any comments welcome!
Cheers
Gareth

[S600VXR]

Have you run a DTI on them Gareth to check they are runninbg true.... might just be a tiny bit of debri causing them not to sit straight... I know when ever I do disks I clean the hubs faces spotlessly clean and the disks themselves. Doubt they will be warped as they are floating rotors which tend to stop that happening.... iirc

[gareth h]

No I was going to but they looked in such good condition I didn't bother, doh!
If they do have pad residue would a few heavy braking sessions clean the discs or make them worse?

[S600VXR]

Id be tempted to take them all off and give everything a really good clean mate then re-assemble very carefully making sure no "bits" drop from other areas between the mating surfaces. Then give the disks a good rub with some emery paper and then try them out.

[stigmundfreud]

gareth check for st in them first the juddering if its fairly violent would suggest a but if st stuck that needs to clear out - you did change the fluid etc after the change?

[Miffy964RS]

I would imagine they are 'warped'. I did the same thing to the first set of AP discs I had on my STI because I was stupid. You can replace the discs without replacing the centre alloy 'top hats'.

Bedding in high performance discs like these is a careful and time consuming process. If done correctly they should then be problem free.

Discs don't actually become warped as such, which is why skimming them will not fix them. I won't go into the boring metallurgical details here.

[V8HSV]

gareth h said:

I picked up a set of AP brakes off e bay (branded HSV), they have been fitted and I'm getting a pulsing through the brake peddle and a slight shaking of the steering wheel, unfortunately because they looked in such good condition I didn't check the discs for trueness before they were fitted.
When you use them hard the pulsing disappears and they work very well, is it likely they are warped? if so anybody know how much front discs are?
I've read about the transfer of pad material to the disc giving the same effect, if this was the case would it be obvious (the discs looked clean before they were fitted).
Any comments welcome!
Cheers
Gareth

Experienced exactly the same, mine were warped but on the inside of the disc with everything looking ok from the outside, can be a hefty wait from AP to replace. If yours are in good condition/thickness you might be able to sort by re-facing the discs, good luck anyway.

[gareth h]

Thanks, they seem to have improved a bit with use, due to some agreement with Holden I believe AP can't just supply discs but have to supply bells aswell (what a waste of money/energy/resources!)

[V8HSV]

gareth h said:

Thanks, they seem to have improved a bit with use, due to some agreement with Holden I believe AP can't just supply discs but have to supply bells aswell (what a waste of money/energy/resources!)

That's to ensure new bolts are used rather than use old ones I think