pulsing rear brake/wheel

[claudea]

Hi,

I have a 1992 FZR 600 - Genesis and it has developed a pulsing rear disc brake.

This is enough to cause the rear wheel to lock under braking.

I have had the disc skimmed and they said very little had been rmoved and it’s not warped.
The bike has only done about 30,000 km's and this problem appeared suddenly.

I have tried the following:

With the bike off the ground, spinning the wheel with the pads in place is enough to notice them contacting just one spot.

Have removed the disk,
. Checked the 6 mounting points for the disk and they’re all clean
. Lightly sanded this area on the back of the disk with 1000 wet and dry.
. Cleaned the threads with a tap and they’re good.

After cleaning all the bolts I have used Loctite (blue) on the bolts each time the disk was remounted and the wheel checked on the bike.

Steps taken so far with the bike on a stand and the pads removed:
. With a dial gauge on the disc there is a high spot/ run-out of .012mm
. Rotated disk and the spot is always on the same position on the wheel.
. Tried another disc on my wheel and the high-spot / run-out was 0.006, same position on the wheel.
. Tried another wheel
- with my disc and same result
- with another disk same result.

Axel is straight.
All wheel bearings have replaced, but no change.
I have also checked it without fully tightening the axel but there is no change.

Next step today is to retry and get an accurate measurement on the wheel itself and check the vsariance.

I have run out of ideas on what could be wrong and how to correct the problem.

One suggeestion is sanding down the disc mounting points ton the wheet o remove the high spot - but I'm not very keen on this.

Any thoughts or suggestions.

 

[Stumbles06]

Wow, very thorough checking you've already done. I'm at a loss, unless the wheel isn't aligned exactly, but seeing as you've changed wheels, I can't see it being that.

Good luck with the problem, hope you get it sorted.

Oh yeah, and :welcome: to the forum, another Aussie :thumbup:

If you get a chance, stick a couple of photo's of your bike in here, don't see many of the older FZR 600's around.

 

[cashcrzzy]

Does the rotor only go on 1 way ? Remove the rotor and look at the wheel where the warpage is,is the wheel cut differently there ? Are all of the holes on the rotor the same size ?Is 1 bigger or smaller ?
Cant help you any more sorry
Did you read the repair manual ?
Greg A.

 

[wrightme43]

Its going to be alot of work.

Several ideas.

Mark the high spot. Mount the disc at 90 degree clockwise to where it is now. If the high spot moves, have the wheel mounting surfaces, milled flat at a machine shop. If the high spot stays the same have the disk mounting surface and braking surface milled at a machine shop. Have you tried new brake pads as well? Is one of the bolts stretched a bit and not holding torque like the rest?

Hope it helps.

Steve

 

[grommit]

I would find out what Yamaha recommends as the amount of run out that is allowed. If it is within tolerance you should look at the mounting of the disc and caliper.

 

[wrightme43]

runout spec is normally .003-.004 on most vehicles.

 

[grommit]

runout spec is normally .003-.004 on most vehicles.

3 to 4 thou sounds reasonable but he's talking mm.