Wobbly new discs

**Carldav** · 10th August 2008, 14:01

I fitted some petal rotors to the front of my GSXR this weekend, along with some new H-H EBC pads. The instructions that came with the discs say give them 200ks to bed in (and don't hammer them before then). The thing is, when I do brake (moderately), the front shakes like it never did before on my old discs. I'm worried that this means the discs are out-of-true and will need machining (this would really piss me off, given how much they cost, and how hard they were to fit - I don't have a front axle stand). What are the odds that this shaking is just a normal part of the disc bedding in procedure, and that it will sort itself out in those next 200ks?

**Tony.OK** · 10th August 2008, 16:13

When you say shaking are you meaning side to side or more of a judder?
Sometimes new pads can cause a judder (backwards n forwards)until they bed in properly.
If they were warped you can feel it in the lever if its bad and you'll notice extra travel in the lever when you go to use it again as the warping can push the pads back in a bit.
Have just done new pads in mine and they juddered a bit for the first few light applications, warm em up and then start giving it some berries, they should come right.
Good luck

**Carldav** · 10th August 2008, 16:35

Yes 'judder' is a much better description. It's almost like a pulsing from the front end. I was going to run the brakes in slowly, but I've been reading on-line that multiple back-to-back braking from high speed (not to a dead stop) might be a better way to get the job done.

**Tony.OK** · 10th August 2008, 17:33

Originally Posted by Carldav

Yes 'judder' is a much better description. It's almost like a pulsing from the front end. I was going to run the brakes in slowly, but I've been reading on-line that multiple back-to-back braking from high speed (not to a dead stop) might be a better way to get the job done.

Just get them warm 1st to reduce risk of warping

**Devil** · 22nd August 2008, 09:13

Can you confirm that you can feel a warp when gently slowing to a stop from 30km/h or so? (usually the most obvious place).
If you dont feel it there, but get a shuddering when braking at higher speeds then one other thing to consider is you may have done the front axle up too tight.
If you pinch the forks together the suspension can have a hissy fit and start cavitating under braking, felt as a shudder.
Get the front end off the ground and check the lineup of the calipers vs the rotors, that can often be the easiest indicator that the forks are being pulled together too much. Make sure the wheel spins freely.

**koba** · 22nd August 2008, 10:26

If you have no luck with the stuff above and are still worried after that you can put radial vivid marks on the disks at regular intervals, a couple of centermetres apart at the disk edge, to see if they rub off evenly.
This shows where the disks and pads are making contact and where they are not.
If they are decently warped it should become fairly obvious, maybe take a photo to show whoever you bought them from.