34 BMW 1983 R80ST Install Rear Brake

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.

Rear Brake Components

Rear Brake Components

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.

Rear Brake Shoes Installation Parts

Rear Brake Shoes Installation Parts

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

Rear Brake Pivot Shaft Details

Rear Brake Shaft Details

Rear Brake Pivot Shaft With O-Rings and Washer Installed

Rear Brake Shaft With O-Rings and Washer Installed

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.

Install Brake Pivot Shaft Into Hole In Rear Drive Housing

Install Brake Shaft Into Hole In Rear Drive Housing

Brake Pivot Shaft Installed

Rear Brake Shaft Installed

Brake Grease

Brake Grease

Brake Grease On Round Pivot Shaft

Brake Grease On Round Pivot Shaft

Brake Grease On Cam Of Pivot Rod

Brake Grease On Cam Of Rear Brake Shaft

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

New Brake Shoes As The Fit Inside The Rear Drive Housing

New Brake Shoes As The Fit Inside The Rear Drive Housing

"D" Stamped On Top Brake Shoe

“D” Stamped On Top Brake Shoe

"S" Stamped On Bottom Brake Shoe

“S” Stamped On Bottom Brake 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.

Brake Shoe Return Springs Are The Same Length

Brake Shoe Return Springs Are The Same Length

Brake Return Spring Installed On Brake Shoes

Brake Return Spring Installed On Brake Shoes

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.

Install Rear Brake Shoes Over Round Pivot Rod

Install Rear Brake Shoes Over Round Pivot Rod

Install Snap Ring In Groove Of Round Pivot Rod

Install Snap Ring In Groove Of Round Pivot Rod

Snap Ring Secures Brake Shoes On Round Pivot Rod

Snap Ring Secures Brake Shoes On Round Pivot Rod

Push Other End Of Brake Shoes On Either Side Of Rear Pivot Shaft Cam

Push Other End Of Brake Shoes On Either Side Of Rear Shaft Cam

Push Other End Of Brake Shoes On Either Side Of Rear Pivot Shaft Cam

Push Other End Of Brake Shoes On Either Side Of Rear Shaft Cam

Push Other End Of Brake Shoes On Either Side Of Rear Pivot Shaft Cam

Push Other End Of Brake Shoes On Either Side Of Rear Shaft Cam

Verify Snap Ring Is Fully Seated In Groove Of Round Pivot Rod

Verify Snap Ring Is Fully Seated In Groove Of Round Pivot Rod

Rear Brake Shoes Installed On Back Of Rear Drive Housing

Rear Brake Shoes Installed On Back Of Rear Drive Housing

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.

Temporarily Install Rear Brake Lever On Splines Of Rear Pivot Shaft

Temporarily Install Rear Brake Lever Arm On Splines Of Rear Brake Shaft

Rotate Rear Brake Pivot Arm To Open Brake Shoes

Rotate Rear Brake Lever Arm To Open Brake Shoes

Rear Shoes Open Enough To Slip Anti-Squeal Rubber Boot Over Rear Return Spring

Rear Shoes Open Enough To Slip Anti-Squeal Rubber Boot Over Rear Return Spring

Brake Anti-Squeal Rubber Sleeve Installed On Rear Return Spring

Brake Anti-Squeal Rubber Sleeve Installed On Rear Return Spring

Install Rear Brake Foot Pedal & Connecting Rod

Rear Brake Foot Pedal Installation Parts

Rear Brake Foot Pedal Installation Part

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.

Install Rear Brake Foot Pedal

Install Rear Brake Foot Pedal

Rear Brake Pedal Rod

Rear Brake Pedal Rod

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.

Rear Brake Pedal Rod Installed

Rear Brake Pedal Rod Installed

Rear Brake Rod Attached To Top Of Rear Brake Foot Pedal With Special Pin

Rear Brake Pedal Rod Attached To Top Of Rear Brake Foot Pedal With Special Pin

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.

Install Rear Brake Foot Pedal Pivot Bolt

Install Rear Brake Foot Pedal Pivot Bolt

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.

Install Rear Brake Light Switch Activation Bolt

Install Rear Brake Light Switch Activation Bolt

Rear Brake Light Switch Activation Bolt Installed

Rear Brake Light Switch Activation Bolt Installed

Rear Brake Foot Pedal Installed

Rear Brake Foot Pedal Installed

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.

Install Rear Brake Arm Felt Washer

Install Rear Brake Lever Arm Felt Washer

Install Rear Brake Pivot Shaft Lever Arm On Pivot Shaft

Install Rear Brake Lever Arm On Rear Brake 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.

Rear Brake Pivot Shaft Arm Installed

Rear Brake Lever Arm Installed

Brake Pad Wear Pointer

Brake Pad Wear Pointer

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.

Install Rear Wheel Cone

Install Rear Wheel Cones On Rear Drive Studs

Install Rear Wheel Nuts

Install Rear Wheel Nuts On Rear Drive Studs

Rear Wheel Installed

Rear Wheel Installed

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.

Adjust Rear Brake

Adjust Rear Brake

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.

All Done

All Done

All Done

All Done

2 thoughts on “34 BMW 1983 R80ST Install Rear Brake

  1. I just love the shine and cleanliness on all the work you do. It is like a brand new bike off the assembly line! Thank you for sharing your labour of love!

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