The rear brake on the 1983 R80ST is a drum brake.

Parts

All the parts are supplied by Euro MotoElectrics for free in support of my goal to auction this bike and send all proceeds to support the Motorcycle Relief Project.

I replace the brake shoes with new ones. Most of the rear brake parts came with the bike with the exception of some hardware. I replaced the return springs and retaining clip on the brake rod. I also install a later item that is a rubber piece that installs on the rear brake shoe return spring that is designed to eliminate brake squealing.

Part #	Description	Qty
34 21 2 310 523	SET: REPAIR KIT BRAKE SHOE ASBESTOS-FREE – 25MM 2 BACKEN	1
34 21 1 457 091	TENSION SPRING	2
34 21 1 457 572	ABSORBER, On Bottom Spring, Anti-squeal	1
07 12 9 934 961	PIN – 6X12, Brake Rod	1
35 21 1 230 360	GASKET RING, Brake Pivot	1
07 11 9 906 328	O-RING – 10X2 (to 09/83)	4

Here are all the parts for the rear brake.

Video

This is a video summary of how I install the rear drum brake on the 1983 R80ST.

VIDEO: 1983 BMW R80ST Install Rear Brake

Install Brake Shoes

Here are the parts I use to install the brake shoes.

I start by installing the four O-rings and the metal washer on the rear brake shaft.

Then I insert the rear brake shaft in the hole in the rear drive housing from the brake shoe side of the housing. Then I put some brake grease on the cam of the shaft and on the round pivot rod.

The brake shoes are marked with a “D” on the top shoe and a “S” on the bottom shoe.

The brake shoe return springs are the same length. I install one next to the end of the shoes that go over the round pivot rod in the rear drive housing.

I leverage the shoes over the round pivot rod in the rear drive housing. I install the snap ring to secure that end of the brake shoes on the round pivot rod. Then I install the second spring on the other end of the brake shoes and push the shoes apart so I can get the ends on either side of the cam face on the rear brake shaft. Then I check the snap ring to be sure it’s fully seated in the groove on the round pivot rod.

I temporarily install the rear brake lever arm. Then I push it to open up the brake shoes so I can slip the red rubber squeal damper over the rear brake shoe return spring. The flat face of the rubber damper fits against the shoes.

Install Rear Brake Foot Pedal & Connecting Rod

I install the rear brake foot pedal into the gap between the rear frame tube and the rear brake light switch. I let it hang there so I can install the rear brake rod onto the end of the rear brake foot pedal.

I push the rear brake foot pedal up so I can access the hole at the top that the special pin that fits into to secure the rear brake rod to the rear brake foot pedal. I balance the rear brake rod on the rear shock so it’s easier to install the special pin and rotate it so the sleeve on the end of the pin fits onto the collar of the rear brake rod.

Then I install the rear brake pedal pivot bolt into the hole in the frame. I put a bit of wheel bearing grease on the shank of the bolt then a flat washer under the bolt head and the other flat washer against the frame and install the locking nut.

Next I install the adjustable bolt that activates the rear brake light switch. The hole in the tab of the rear brake pedal is sized to fit an M8 bolt. I use two nuts so I can lock the bolt in place after I adjust the length of the bolt so the brake light goes on after only a small rotation of the rear brake pedal.

I install the rear brake lever arm onto the splined end of the rear brake shaft. Before I do, I install the felt washer against the rear drive case. I use a screwdriver in the slot to open up the brake lever arm so it’s easy to slide on. Then I use a plastic mallet to tap the lever all the way onto the shaft.

I install the barrel into the holes in the rear brake lever arm and screw on the wing nut. Then I install the pinch bolt with the brake pad wear pointer into the hole in the top of the lever arm The BMW logo on the lever arm should face to the rear.

Install Rear Wheel

Before I install the rear wheel, I spray some brake cleaner on a clean blue shop towel and wipe down the brake pads and the brake hub inside the rear drive so there isn’t any grease or debris that would foul the brake pads.

I hang the rear wheel on the three studs of the rear drive. I install the cones on the studs and then the nuts and tighten them finger tight. I’ll torque the nuts to 75-80 Ft-Lbs after I get the rear brake adjusted so I can press down on the rear brake pedal to keep the rear wheel from turning while I torque the nuts.

Adjust Rear Brake

I adjust the wing nut on the end of the rear brake rod while I turn the wheel until I hear the brake shoes start to touch the drum. I back off the wing nut one turn. Then I adjust the rear brake light switch adjustable bolt so the brake light comes on with only a small movement of the rear brake foot pedal.

After I adjust the rear brake, I push on the rear brake pedal with one hand while I torque the three rear wheel nuts to 75 Ft-Lbs.

All Done

Here is what all done looks like.