Brake Disc Wobble

[Metallicat]

After replacing my jackshaft / driveshaft bearings I noticed that the brake disc does not run true. There is a noticeable wobble as if either the shaft or the disc itself is out of round. The chaincase halves went on without any problems. I can't really believe the shaft is bent. When I say "wobble" I mean vertical movement as the shaft rotates, so as the disc turns it protrudes above the top of the brake pads on the high side, and it is about even with the top of the pads on the low side. I have no idea how much run-out it had before changing the bearings as I never paid attention to it before.

 

[Metallicat]

It is the disc that is out of round. I will probably not worry about it. It could have been that way since day one. Total runout is 1mm, maybe a bit more. I took it off and ran the sled, the jackshaf seems to turn true. So I put the disc back on without the key and spun it on the shaft and saw that it is not centered perfectly on the hub, so it has a bit of a wobble to it.

 

[J1635]

i thought the same thing when i took mine apart. after doing some reading on here its ok apparently. they call it a floating brake system, or floating brake disc? search on here

 

[APEX 06]

J1635 is right

 

[Metallicat]

It floats laterally on the shaft so there will be some side to side movement. Mine also acts like the hub isnt perfectly centered on the rotor which has nothing to do with float. As it rotates it appears to move up and down, not just side to side between the pads.

 

[J1635]

your saying the brake disc isnt spinning a true circle like its pulsating? is the disc hub oval shaped? my keyway was worn out which was causing even more play, cut a new piece of 1/4" keystock, do you have all the shims and washer installaed in the correct spots? are all of the balancing weights still on the disc?

from what your describing it sounds like the disc is oval'd out causing it to run like that, in which case i would just get a new disc because that will eventually stress your driveshaft and who knows what else, disc is cheap.

I was also thinking about use this stuff Loctite makes that is like superglue for the keystock, but when i think about how many rpm's these shafts and disc spin, it needs that play in it otherwise things would bust up, replace disc and call it a day i think

 

[Metallicat]

Yes, the disc does not spin in a true circle. The center hub isn't ovaled out at all. All shims and spacers are in the correct positions. The shaft is straight. The rotor itself is out of round. Measuring from the center hub, there is at least a 1mm difference from the hub to outer disc rim as the rotor turns. Might have to get one from barn of parts. The rotor otherwise is in good condition.

 

[J1635]

ohh ok now i know what you mean.

i dont know how much a disc is, but you could probably have a machine shop true that up for you, providing they dont take off so much material that braking is affected?