Help with Rear Disc Brakes By justguy1 (Read 1,438 times)

[justguy1]

My rear disk brakes are keeping my rear wheel from turning freely. I took the brake caliper off and then opened up the piston.. put it back on and before I squeezed the brake I check to see if the wheel would move and it moved a little. Then after squeezing the brake a few times till it felt hard, I noticed again that the piston was not opening up that its tight on the rotor.. Any suggestions on how to adjust this so the wheel moves freely?? I started the scooter, revved it a little then it stops abruptly because of the wheel not moving freely. Anyone?? Anyone? Buhler??

[sprocket]

There are no adjustments on Chinese callipers...

Did you bleed the brake fluid? You could have an air pocket?

Which side is dragging? One pad moves the other does not.

You may need to shim the calliper to get the rotor in the center of the calliper.

Or shim the rotor to move it out from the wheel

The rotor could be too thick (I have seen that happen). They may be the wrong pads

[justguy1]

Its the side with the pistons.. They are opened but not going back in.. Maybe they don't go in.. I dont know.. The thickness on the rotor is 3mm which i think if standard. It looks like the brakes squeezes but doesn't release back.

How do I shim the brakes?? Maybe that will help.. Just another thing on this possessed scooter...

[sprocket]

The piston sounds like it is sticking. I would take the calliper apart and see if you can get it working better. Maybe the seals are sticking? Use a C-clamp and press the piston back in, then squeeze the handle and repeat , repeat , repeat...

The callipers on these things allow the brake pads to ride on the rotor. They just ride there and squeak and are generally a pain in the arse.

But your problem is different. Try and loosen it up and then if you still have the same trouble I would replace the calliper...

To shim the brakes you slip thin metal (washers) between the calliper and the mounting. I use little washers I cut them from coke cans... You may need two or three under each bolt. The tighten the bolts that hold the calliper to the mounting...

[Cruiser]

The caliper is a floating assembly. It slides back and forth on the mounting bolts. There is always a slight drag on the rotor because the pads are normally in light contact with the rotor. The pistons do not retract unless they are pushed back.

Excessive brake drag is usually caused by one of two things. Either the piston(s) is sticking in the caliper because of rust or dirt or the caliper is not sliding on the mounting bolts also caused by rust or dirt. If the piston(s) is sticking, it's time to replace or rebuilt the caliper. If the caliper is sticking, then the bolts should be removed and cleaned up.

Do not ever squeeze the brake handle unless the brake assembly, pads, and wheel is mounted. If not, then you will probably pop a piston out of the caliper with a brake fluid dump following.

[jhbietz]

Just a thought. I had a customer bring in a 150cc with a the same problem. Turned out they had taken the back wheel off to replace the tire and had forgotten to put the spacer back in. When they titened the axle nut it pulled the swing arm in too far and made the break drag.