Rear drum brake - 125cc  By  gingel (Read 1,473 times)

Some brakes squeak. Some squeak a lot depending on the material the brakes shoes are made of. If your brake drum is not perfectly round that would make it drag part way around.

You may be able to clean up the drum surface with some fine paper if there is a rusty spot or something. Otherwise if it's truly out of round I think the only solution is to replace it.

As a test you could pull the brake shoes off, then put the wheel on temporarily and turn it by hand to verify that the problem is the brakes rubbing and not elsewhere in the drivetrain.

Is there some sort of rubber weatherproofing ring between the wheel and the swingarm that might be catching when you snug the wheel in place?

It's very common in chinese scoots to have the drum brake pot being bored out of center.
It takes a few hundreds of miles of braking for the pads to rub off the unevenness.
Sanding won't help, as the brake pads are basically performing that function on the drum.

there are 2 things you can do. If the brake pulse is really hard, loosen the nut a bit, and drive with a looser rear brake. You should be braking with the front brake at all times anyway, and mostly only use the rear brake for emergencies to aid out the front brake.

Second option would be to tighten the nut to where the pulsing is very gentle. While you'll be riding the brake pads will level the unevenness, and after a few hundred miles, readjust the nut one click further.

Just as long as the pulse (braking unevenness) is not too much, and would cause excessive heat, there is no problem.
Most tires have aluminum rims, and aluminum is a great distributor of heat, so your pads won't burn out from scraping against the braking pot a bit every rotation.

Brake drums regularly get out of round and cause this. You can have a machine shop turn them to true them up if they have warped too badly. If moderate you can leave the shoe dragging a bit but that could take some time to true it up.

On a single swingarm bike there is the possibility that after going through a pothole you have bent the output shaft that the rear wheel mounts on or damaged the dearings which would also make the brakes rub unevenly. Then you would need to replace the output shaft and bearings.

I'll see if it will be ok in the next few hundreds miles.

The bearings of the output shaft looks ok, because i tried to move it
to all side and it pretty solid.


Do you mean tightening the drum brake, after you can't turn the nut anymore? Is that recommended? Can you post a picture?

The problem will not be solved after riding 100 miles, but after 100 miles of braking; so yes, it will take long time.
Sometimes it helps braking a bit on the aggressive side with the rear brake only, until the brakes settle. Once the brakes settle, they'll be more effective to reduce unevennesses. If they're fairly new, they might need to settle first, before they can actually start scraping off the wheel.
I would tighten the nut to where you have difficulty rotating the wheel using one index finger on the tire. If you tighten it too lightly, they might take forever to even it out. If you tighten it too hard, where it becomes difficult to turn the tire, even by hand, you might burn the pads.

Just point at your tire, touch it with the index finger, and with the index finger stretched, try rotating the tire 360 degrees. You're good if you can rotate the tire, and only have a slight difficulty on that spot where the brakes are dragging.

I will post a pic about adjusting the arm. These drum brakes are made so u hav to adjust the arm to get the full use out of your brake pads. Its always good to make sure you still hav pad left before adjusting th arm just to b safe. I wasnt even close to rotating the inner tension paddle past the apex. Like i said these at least most o these china scoots are made so you have to adjust the arm. Let me know if u need a pic