Tuning Brakes

[rickytile]

i have a 64 cb77 that i have rebuilt completely. i have reassembled the brakes, but the pressure is awefully loose and braking is poor.. i tried to adjust the cable/arm one click up on the splines of the hub cover and it starts to rub at starting position. im not sure what to do at this point. please advise

[Spargett]

Hey Ricky,

The brake arms should have very tiny punch marks that can be aligned on the cam's splines. That'll line everything up inside. I'll try to break down the process in a few simple steps. Prop a lift under the bike to get the front wheel a few inches off the ground.

1. Turn your fine adjuster on the handlebar perch "in" all the way (righty tighty).

2. Now the two brake arms should be just about parallel to each other. The idea is that each of the two pads expand at the exact same time when you pull the level. If you can eyeball them so that they're parallel, that should put you in a good spot.

3. Tighten the cable up on the crude adjustment on the wheel until you here the brakes just barely start to drag, then back them off just a little.

4. Go back to the level's fine adjustment and take up any slack till you've got about 1/8" of freeplay.

If the brakes still aren't feeling very well, go back to step three and get the brakes to drag a little. Keep spinning the front wheel while adjusting the connecting rod between to the two arms. As it rotates you should hear a *shhhkkk* sound as the brake pad rubs at the highest point. As you experiment with expanding or contracting the opposite pad you'll begin to hear a slightly delayed *shhhhkkk.... shhhhkkk* as the wheel passes one, then the other. As you continue to make your adjustments the two sounds should become closer and closer until they're right on top of each other. That's how you know they're pretty much even. This part takes some finesse and patience. As you make adjustments in one place, it's gonna slightly change them somewhere else. So move slowly and methodically.

Let me know how that goes for you. You say you've completely rebuilt the bike, does that include opening the wheels up and checking the state of the internals?

And if anyone else would like to contribute, there's certainly more than one way to skin a cat.

-Scott-

[rickytile]

thanks. i will try this out. after a little use, i did pull the unit out and noticed the new shoes i have put in were only making solid contact on the outside and that the liner in the hub was i little more eroded or worn in the middle. not sure if breaking in the shoes will suffice, or if i need new liners put in. i sure hope not!

[teazer]

It might be good to have the drums machined so that they are completely round. Any machine shop with a gap bed lathe should be able to do them, or send the wheels to Vintage Brake.

Then get the shoes machined on the brake plate to match the exact diameter of the drum.

[rickytile]

I was scared about that. Would that lathe procedure require removing the rim and tire?

[teazer]

No. You could strip the whole wheel and machine the bare hub but it might pull out of round when you lace it back up.

But let's not panic - yet.

When you apply yhe brakes gently are they catching say every half a wheel revolution (drum oval) or are the shoes just not making contact?

Take the wheel off and rub chalk ( white board markers are not the same...) and reassemble the wheel. Spin it and apply teh brakes. Pull the brake plate out again and see which areas the chalk is not rubbed off.

That will give you a good idea of what needs to be done.