Topic: interesting rear brake issue????

[J.Webster Designs]

hey guys i have the old girl out on the road now and i have noticed that when applying the rear brake about half way, the rear feels like it wants to jump out to the right. not a significant jolt or anything but enough to where i can feel it bump over to the right a little bit. It caught me by surprise the first time getting the bike out on the road. anyone have any ideas on what could be causing this? I talked with some of the guys i know and one said that he had the same problem on a buell blast and it ended up being the tires. however, I am running the Avon Road Riders and have not seen any problems like this from other users. kinda makes me afraid to go past half way on the rear brake so i want to get this sorted before i need that rear brake to work properly.

Let me hear your thoughts.

1976 CB750F

[Spanner 1]

Brake caliper is on the right ( jump ) side.......hmmmm....shot wheel bearings, mostly the one in the left ( sprocket ) hub......yes, it happened to my bike.
In my case the swing-arm bushings were shot also....put on mainstand, grab back wheel and try to rock wheel left to right is the test for that......

[Berek]

loose hub nut and one of the adjusters maybe?

[BeSeeingYou]

loose hub nut and one of the adjusters maybe?

Same thing happened to me when I forgot to tighten up the hub nut after adjusting the chain. Doh!

[J.Webster Designs]

is the hub nut the rear axle nut? how tight should it be? i did the rock back and forth deal... didnt feel any play.

[J.Webster Designs]

bump. anyone know how tight the main rear axle nut should be without putting a torque wrench on it?

[Gordon]

bump. anyone know how tight the main rear axle nut should be without putting a torque wrench on it?

It's difficult to quantify how tight a bolt should be without using torque numbers. 

I'd say really freaking tight.  That's how I do mine. 

[MCRider]

bump. anyone know how tight the main rear axle nut should be without putting a torque wrench on it?

On the 72K the axle nut is 75 Ft lbs +/-. So thats 150 lbs on a 6 inch wrench. So I stand on the wrench at about 6 inches. Close enough.

[MCRider]

is the hub nut the rear axle nut? how tight should it be? i did the rock back and forth deal... didnt feel any play.

Was it on the center stand? was the chain loosened up? Slide the wheel all the way forward and then tighten it. Remove the lower shock mounts, with a prop under the wheel at about that level. Everything must be out of the way. Now test for swingarm bushing slop.

You've got a problem somewhere, safety issue.

[mcpuffett]

worn swingarm bushes?

[BeSeeingYou]

If you have eliminated the swing arm and the axle nut as the problem I would hazard a guess and say it is the brake caliper.  It is a twin piston caliper and maybe one piston is stuck or slow thus causing it to pull to one side.  If you decide that you need to rebuild the caliper PM me as I came up with a way to get it apart that is better than the book.

[J.Webster Designs]

yes, it was on the center stand. I will have to loosen the axle completely so and try then. however, I dont see how the tightened chain would keep the movement of the swing arm from happening as there is about 1 inch of free play. but i will try it just in case. I dont have my torque wrench right now so i will have to try to hunt one down from a friend. I have a feeling that i do not have the main axle nut tightened properly. I will report back with my findings. Thanks guys.

[754]

Last guy that had a similar problem..
 was missing a washer on the axle, under the nut..
nut was tightening on the shoulder, but not clamping the swingarm..

[J.Webster Designs]

have the washer. just dont think i torqued it properly.

[MCRider]

yes, it was on the center stand. I will have to loosen the axle completely so and try then. however, I dont see how the tightened chain would keep the movement of the swing arm from happening as there is about 1 inch of free play. but i will try it just in case. I dont have my torque wrench right now so i will have to try to hunt one down from a friend. I have a feeling that i do not have the main axle nut tightened properly. I will report back with my findings. Thanks guys.

My point being you have a problem and should stop at nothing to find it. In order of probabilities: swingarm bushings. If its not obvious, then loosen the chain, remove the lower shock mounts (but support the wheel), even back off the torque from the swingarm pivot. The clamping action of the pivot bolt may be masking the wear of the bushings. Riding it and activating the brake puts way more leverage into the system than you can do with just your arm and a side to side push/pull.

If for sure alls well, tighten things back up and go to wheel bearings, brake caliper etc.

Torque on the axle nut while important, is way down my list, based on your symptom.

But it could be.

[J.Webster Designs]

thanks MC i will be getting out there this weekend to check it out.