I think I need a new rear axle 1978 GS750

[Guest]

When I brake with the rear brake just before total stop I can feel the rear brake disc has a wobble. So, I put it on the rear stand in first gear. The brake disc and the sprocket have the same wobble. One time per rotation. I figure it must be a bent rear axle to create a symmetric wobble. Can I buy a new rear axle anywhere or does someone here have one for sale that is straight?

[bwringer]

It's not the axle. The axle doesn't rotate.

Remove the wheel and look for the real cause.

Check the bearings in the wheel and the sprocket carrier, and make sure the hub and sprocket carrier aren't cracked or damaged where the bearings seat. Make sure all the spacers are in the proper places.

[sugi]

I just took everything apart. The brake disc is nice and flat, so is the sprocket. The axle seems nice and flat. I checked the bearing which I replaced 1 year ago. they all seem ok. The sprocket carrier seemed to be a tiny bit wobbly because the bearings were tight so I it would not seat properly 100%. Fixed that. checked all the spacers and bearing. Seems everything is ok. Put everything back together and still a slight wobble. I can ride with it and don't even notice but again when I brake I can tell just before the bike stops the brake disc drags intermittently. It seems to me that the center hub is also showing the same wobble. brake disc, center hub and sprocket have the same wobble. I could not see a crack in the sprocket carrier. Not sure what is up. Could the bearings or a bearing be the culprit?

[hjfisk]

When you replaced the bearings did make certain that they seated properly when installed?

[sugi]

Ok here it goes. I took everything apart 2x. Rechecked the bearings spacers hub sprocket carriers etc. all seats properly and looks perfect. Well I had a hunch. I adjusted the spokes so I would get no wobble in the brake disc. Now the brake disc and sprocket runs dead straight but there is a huge wobble in the rim. HAHAHA. When I relaced the old rim I must not have realize the rim was bent and when I trued the wheel the tension was too great on the hub and twisted it somehow a little. I can pick between a true rim or a true hub but not both. So I think I need a new rim.

[sugi]

I trued my rim after the hub was running straight. Instead of tightening I loosened some spokes first before I tightened the opposing spokes. This way I could keep the hub and rim true. Now I have both running very true. I simply had too much tension on some spokes. Live and learn. LOL

[bwringer]

Thanks for posting your findings!

I had no idea uneven spokes could pull a hub out of alignment that much.

[sugi]

I could not believe that was my problem. I would have never thought that could happen but I can't explain it any other way. Strange indeed unless you are me and use the spoke nuts for a workout
LOL
Believe it or not. I prefer my 1978 GS750 to my 1199 Ducati
Panigale for commuting any day of the week.