The 1983 R80ST has a single front disk brake. The brake disk is mounted on the right side of the front wheel. This bike did not have the front disk, so I got a new one. I rebuilt the front brake caliper and you can see how I do that here.
All the parts for installing the brake system were provided free of charge by Euro MotoElectrics in support of my goal of auctioning this bike and donating all the proceeds to support the Motorcycle Relief Project. The disk brake rotor hardware was included in the stainless steel fastener kit I bought.
|34 11 1 236 005||BRAKE DISK, Front||1|
|07 11 9 901 038||FILLISTER-HEAD SCREW – M8X70-8.8-ZNS, Rotor||5|
|07 12 9 904 002||SELF-LOCKING HEX NUT – M8-8-ZNS3, Rotor||5|
|34 11 2 302 077||WASHER, Rotor (5)||5|
|34 32 1 238 258||BRAKE PIPE RIGHT||1|
|34 32 1 242 106||BRAKE HOSE||1|
|34 32 1 237 259||GROMMET, Triple Clamp Hose Clamp||1|
|34 32 1 236 462||GROMMET, Pipe To Brake Hose||1|
|34 32 1 242 269||HOSE CLAMP, Brake Hose On Triple Clamp||1|
|34 32 1 237 256||HOSE CLAMP, Brake Hose On Fork Slider||1|
I use the Air Zapper which is a vacuum brake bleeder to help get the air out of the front brake system
Here is a short summary video of how I do this work.
VIDEO: 1983 BMW R80ST Install Front Brakes
Install Brake Hose Brackets And Grommets
There are two brackets that route the brake hose. The upper bracket mounts on the right lower fork yoke pinch bolt. It has a split grommet that fits over the brake hose that I’ll install when I route the brake hose down the fork tube. The lower bracket mounts to the right rear fork brace bolt. The outside of the bracket fits next the the Allen head of the bolt and the inside fits next to the inside of the fork brace. The grommet fits in the hole of the bottom bracket.
Install Brake Hose
The brake hose I got from EME is a braided steel brake hose.
In order to install it, I loosen the right handlebar control on the handlebar and slide it out on the handlebar. Since the fitting on the end of the brake hose is solid and does not turn, I rotate the brake hose to tighten the fitting into the hole in the front brake master cylinder.
Then I route the brake hose behind the headlight shell and down and out on the right side. I rotate the right handlebar control until the brake hose touches the underside of the dash and tighten the handlebar pinch bolt.
There is a bracket with a grommet that mounts on the lower yoke pinch bolt. I insert the split rubber grommet around the brake hose and push it into the bracket.
There is another bracket that mounts on the right side, rear fender brace bolt. The top of the brake hose fitting sits on top of the rubber grommet. The steel brake pipe screws into the brake hose fitting and into the inside hole in the brake caliper.
Install Front Brake Caliper
Then I mount the brake caliper on the right fork slider and torque the bolts to 21 Ft-Lbs which is lower than the specified 26 Ft-Lbs since I applied anti-seize to the bolt threads. After I mount the caliper, I torque the caliper clamping bolts to 22 Ft-Lbs
I install the steel brake pipe into the inside hole on the brake caliper and then into the brake hose fitting inside the hole of the lower bracket grommet.
Install New Front Disk Rotor
The bike did not have the front brake disk rotor so I got a new one. The stainless steel bolt kit I got included the five Allen bolts with two washers and locking nut on each bolt.
Before I install the front disk rotor, I clean it with brake cleaner on both sides to remove any oil, machining solvent and debris. I also use a Q-tip with a bit of brake cleaner on the tip to clean the inside of each of the holes in the brake rotor.
When I removed the rims and mounted the front tire, I put some tape on the left side of the hub. I verify that the arrow for forward rotation of the tire is on the correct side of the wheel, which in my case is the left side, and then put the wheel down so the right side faces me as the front disk rotor on the R80ST mounts on the right side of the hub.
I insert two bolts with a flat washer on the right side, then tip the wheel up and install a flat washer on each threaded end of the bolts and finger tighten the lock washers. This helps keep the disk rotor on the wheel while I install the other three bolts. I tighten all the bolts and then use a torque wrench and torque them to 15 Ft-Lbs which is a bit less than the lower end of the 16-18 Ft-Lbs specification for the bolts since I use anti-seize on the stainless steel threads.
Bleed Front Disk Brake
I mount the front wheel on the forks.
I fill the handlebar brake fluid cup with fresh DOT4 brake fluid. With the bleeder valve closed I pump the brake lever for a couple minutes to get air out of the master cylinder and the brake lines.
Then I install the Air Zapper vacuum bleeder and start it. Then I open the caliper bleeder valve and pull brake fluid and air out the bleed valve with the vacuum brake bleeder until it looks like all the air is removed. I check the brake fluid reservoir to be sure it doesn’t run dry and refill it twice. Then I tighten the bleeder valve and check the if the brake lever is hard. It is, so I’ve gotten the air out of the front brake system.
Then I pull the front brake lever about half way to the handlebar and wrap a short bungee cord around the brake lever to keep the front brake system pressurized. I leave it that way over night. The pressure will force any remaining air to float up and into the brake fluid reservoir ensuring I get all the air out of the system.