34 BMW 1973 R75/5 Install Front Brakes

Now that I have the front forks aligned and installed, and you can read about how I did that here,

it’s time to put the front brakes back together and install them.  I also add the new handlebars and have replaced some worn parts in the right control assembly or perch.

Parts List

Here is the list of parts I used for this work.

Part # Description Qty
34 11 2 311 079 Brake shoes, Front, set 1
32 73 1 234 515 Front Brake Cable 1
61 31 1 351 646 Front Brake Switch, Rubber Cap 1
32 72 1 230 868 Handle bar grip, Magura, round, right 1
07 32 R kit 002 SS Perch mount Kit SS, Allen head bolts, M6x16
(Hucky’s Part #)
1
32 72 1 231 610 Felt Ring 1
32 71 2 307 401 F Handle bar, USA Chrome, Fehling
(Hucky’s Part #)
1

Resources

The tools needed are standard workshop tools. I also found (was directed to) a neat template created by Scott Scott Lydiard that simplifies alignment of the two brake arms. His site, www.BMWScotter.com is temporarily off-line, but I have his permission to include a PDF file of his template.

Here are links to resources I used in preparation for this work including my link to a correct sized PDF file of Scott’s alignment template.

Front Brake Assembly

I cleaned up the front brake carrier and all the mounting hardware previously so everything is nice and clean.

Front Brake Carrier (Front to the Right)

Front Brake Carrier (Front to the Right)

Front Brake Carrier Inside (Front to the Left)

Front Brake Carrier Inside (Front to the Left)

Note in the picture above of the inside of the face plate there are two circular, hollow pins on the left and right sides. The front brake shoes have holes that mount over these. The brake came shafts go through the holes next to the pins (at the 4:00 position of the left pin and the 1:00 position of the right pin).  Just below and to the right of the left side cam shaft hole is a circular pin that looks like a very large nail head. This is an adjustment cam that I show more clearly later on.

Here is the brake shoe assembly parts.

Front Brake Assembly

Front Brake Assembly

Unlike the rear shoes where there is a different top and bottom shoe, the front brake shoes are the same shape. Between the shoes from the left are the polished brake arms and their cable nipples above them. The two arms are the same and above them are cable nipples and a wire bracket that routes the brake cable along the right fork tube. There is a picture of where the wire bracket goes later on.

To the right are the two brake cams that attach to the brake arms and push the shoes outward against the brake drum which is part of the hub. Each brake cam is different and I show them more clearly later on. The circlips (i.e., snap ring, c-clip) above them secure the shoes on pivot pins on the back side of the brake carrier plate.

The two springs are also different. One has thicker diameter wire with fewer coils (the black colored on on top) so it is a stronger spring. The weaker spring with smaller diameter wire and fewer coils goes in the holes in the brake shoes that are toward the rear of the bike (which is on the left in the picture above) while the stronger spring goes in the holes toward the front of the bike.

The reason for different size springs is to engage the the lower shoe against the drum first (the one with the curved right edge) and then the top shoe (the one with the vertical right edge). The provides more progressive braking than if both shoes contact the brake drum at the same time due to the design of the brakes.

Front Brake Design

The brake design is called double, or twin, leading shoe brakes. The term “leading” indicates that as a shoe pivots on a pin on one side, the other side of the shoe is pushed against the spinning brake drum in the hub. Based on the direction of rotation of the brake drum (clockwise or counter-clockwise) a force is created that acts on the brake shoe but in the opposite direction. For example, if the drum rotates clockwise, the force on the shoe is a counter-clockwise rotation.

Standing on the right side of the bike, if rotation of the hub is clockwise (which is true when the wheel is rolling forward) and the brake shoe rotates counter-clockwise on it’s pivot when the brake is applied, then the resulting force on the shoe as it contacts the hub is a counter-clockwise rotation of the shoe which pulls it tighter against the rotating brake drum so the braking force increases.

Some brakes have a leading and trailing shoe so the brake works equally well when the wheel is rolling forward or backward. For most efficient braking when the bike is moving forward, double leading shoes are used, but they are very weak when stopping while backing the bike up as the force created on each shoe tries to rotate the shoe away from the spinning brake hub.

Install Brake Arm Cams

I put some brake grease on the shafts and the cam face of the brake arm cams before I insert them into the holes. I also put some grease on the outside of the brake shoe pivot pins. I wiped off the excess grease to keep it from getting on the brake shoes and brake drum.

Brake Grease

Brake Grease

Brake Grease on Brake Cam Shaft & Cam Face

Brake Grease on Brake Cam Shaft & Cam Face

The brake arm cams are different and the one with the lever opposite the cam face goes in the front facing hole (to the left in this picture).

Rear Brake Lever Cam With Lever

Front Brake Arm Cam With Lever

The lever rests on the face of the large nail looking adjusting cam. You can see the adjusting cam better in the picture below.

Rear Brake Cam Shaft Lever and Adjustment Cam

Front Brake Arm Cam with Lever and Adjustment Cam

Here is the rear brake arm cam installed.

Rear Brake Cam Shaft

Rear Brake Arm Cam

Next, I temporarily install the brake arms on the serrated end of the brake cam shafts to hold them in place. I’ll adjust the arms on the shafts later.

Brake Levers Temporarily Installed on Brake Cam Shafts

Brake Levers Temporarily Installed on Brake Cam Shafts

Install Brake Shoes

Installing brake shoes with springs can be like wrestling an over-caffeinated alligator while standing on a slippery river bank. The alligator wins 🙂

Here’s how I did it. I put the stronger spring into the brake shoe holes that are toward the front of the bike (to the left in this picture). Then I slip the end of the brake shoes with holes onto the pivot shafts. This is easy since the shoes can overlap and you aren’t fighting the spring.

Front Spring Installed and Shoes on Pivot Pins

Front Spring Installed and Shoes on Pivot Pins

Then I use a screw driver to pry the end of the shoe with the flat face that rides on the cam onto the cam face. Then I just tap the shoes down until they are fully on the pivot shaft and the cam face. This isn’t too hard because you only have one spring to overcome.

Shoes Installed on Pivot Pins and Cam Faces (Front of the Bike is to the Left)

Shoes Installed on Pivot Pins and Cam Faces (Front of the Bike is to the Left)

I use my circlip pliers to install the circlips in the groove on the end of the pivot shaft to keep the brake shoes on the shaft.

Circlip in Pliers

Circlip in Pliers

Circlip Installed on Pivot Shaft

Circlip Installed on Pivot Shaft

Now I install the weaker spring (the one that is toward the rear of the bike, or the right side in my pictures) into the hole of the top brake shoe and with my vice grips, I clamp the bottom hook so the the spring wire rides in a groove of the serrated jaw. Then I sit down on the floor, brace the brake carrier plate with my feet and lean back to stretch the spring until I can hook the curved end into the hole in the lower shoe. Be sure there is nothing behind you should the grips let go or the spring brake and wear eye protection as well. There is a lot of force and spring steel can break sending shards of steel flying.

Attaching Rear Spring Using Vice Grips

Attaching Rear Spring Using Vice Grips

After I installed my springs I read that you can put both springs on the shoes and then mount them on the pivot shafts with the shoes overlapping. They use a large screw driver to lever the ends of the shoes with the flat faces onto the cams.

Align Brake Arms on Brake Cam Shafts

I received a template created by Scott Lydiard (www.BMWScotter.com) via the Micapeak airhead forum from two of the “Headz” and a link to Scott’s site, www.BMWSCotter.com. However, Scott’s site is temporarily unavailable. I contacted Scott and he gave me permission to provide a link to his template which is stored in PDF format. One of the copies I received from one of the Headz had shrunk somehow and didn’t line up correctly.  The one I got from Scott lined up correctly. The link I provided in the Resources section above has the correct size template I received directly from Scott.

Here’s what it looks like.

Scott Lydiard's Brake Lever Alignment Template

Scott Lydiard’s Brake Lever Alignment Template

I cut the template out along the dotted lines and place it on the front side of the brake carrier plate oriented so the two brake cam shafts and the 13 mm nut that holds the adjustment cam are aligned. Then I orient the brake lever arms so they line up with the blue (3) line since I don’t have the brake cable installed.

I don’t have pictures of doing this on my work bench, but here are pictures I took after I mounted the wheel with the brake carrier on the bike. I did a final check to be sure everything was correct.

Scott Lydiard's Template Cut Out

Scott Lydiard’s Template Cut Out

Using Scott Lydiard's Front Brake Lever Alignment Template

Using Scott Lydiard’s Front Brake Lever Alignment Template

You can see the rear lever arm on the left clearly aligned along the blue #3 line and if you look carefully, you can see the front brake lever arm poking out along the the blue #3 line on the right. The template is designed to be used with the wheel installed so it’s is easy to check the brake arm alignment when you want to adjust the brake cable. However, you can’t remove the rear brake lever arm as it interferes with the right fork lower slider. You have to remove the brake arm from the brake carrier plate and rotate the carrier plate so you can remove the rear brake lever arm.

When you have brake lever arms aligned on the brake cam shafts, tighten the Allen head bolts to secure them. I didn’t find torque settings for these so I snugged them to a firm feel, but didn’t oink on them. The lever arms are aluminum and I don’t want to strip the treads.

Attaching Front Brake Lever

Attaching Front Brake Lever

Install Brake Carrier and Mount Front Wheel

Although I wore nitrile gloves when applying the brake grease and was careful to wipe off any that got on the gloves, I clean the brake hub and brake shoes with brake cleaner. Before I do that, I use 320 grit wet paper and lightly sand the brake hub and the outside surface of the new brake shoes to remove any old brake binder from the drum and any surface contamination from the shoes. Then I clean the hub and shoes with brake cleaner and dry them off. Then I put the brake carrier into the wheel hub.

Light Sanding of Brake Hub Surface

Light Sanding of Brake Hub Surface

Front Brake Carrier Inserted into Wheel Hub

Front Brake Carrier Inserted into Wheel Hub

Here is the front axle assembly.

Front Axle Assembly

Front Axle Assembly

There is a spacer sleeve that slides over the axle. The lip on the sleeve rests against the left side bearing cover under the chrome hubcap. I put a light coating of wheel bearing grease on the axle and the outside of the spacer sleeve before installing the sleeve in the wheel using the axle to guide it through the bearings.

Front Axle with Spacer Sleeve

Front Axle with Spacer Sleeve

Spacer Sleeve Inserted into Right Side of Wheel

Spacer Sleeve Inserted into Right Side of Wheel

Then I inserted the axle from the right side through the hole in the lower fork slider, through the wheel hub and through the left lower slider hole.

Install Front Brake Torque Arm Assembly

Here is the polished brake torque arm assembly that keeps the brake carrier from rotating.

Front Brake Arm Assembly

Front Brake Torque Arm Assembly

The torque arm mounts on the stud in the brake carrier and to the right fork lower slider using the bolt, lock nut and washer. I mount the brake torque arm to the brake carrier first and then attach the other end to the left fork lower slider.

Connecting Front Brake Arm

Connecting Front Brake Torque Arm to Brake Carrier Stud

Connecting Brake Arm to Left Lower Slider

Connecting Front Brake Torque Arm to Left Lower Slider

Top Attachment Bolt of Front Brake Arm

Left Lower Slider Attachment Bolt for Front Brake Torque Arm

I torque the brake arm nuts to 12 FOOT/pounds. Then I torque the large 22 mm axle nut to 25 FOOT/pounds followed by the single axle pinch bolt on the bottom of the right fork tube to 12 FOOT/pounds.

Here is what the front looks like now.

Front Brake Hub, Brake Arm & Wheel Installed

Front Brake Hub, Brake Arm & Wheel Installed

Install Handlebars and Right Control Perch

I install the new handlebars and torque the handlebar clamp nuts to 15 FOOT/pounds.

New Handlebars

New Handlebars

Now I can install the right side control perch assembly.

Right Control Perch Assemble

Right Control Perch Assemble

Note this picture below does not show the V-shaped serrated steel wedge described below. I had the control perch powder coated and had to remove the powder coat inside the perch with a drum sanding attachment on my Dremel tool. I install the small serrated steel wedge into the V-slot on the inside of the perch.

Wedge In Perch

Then I slide the perch on the right handlebar end and tighten Allen head bolt to clamp it on the handlebar.

Install Front Brake Cable

The wire bracket is installed under the top, right, fork boot strap.

Front Brake Cable Bracket Installed Under Fork Boot Strap

Front Brake Cable Bracket Installed Under Fork Boot Strap

Here is the new front brake cable assembly.

New Front Brake Cable

New Front Brake Cable

The end that connects to the brake lever goes through a ferrule and has a felt cylinder wiper that fits on the cable.

Front Brake Cable, Handlebar End Assembly

Front Brake Cable, Handlebar End Assembly

The ferrule is slotted on one end and has a larger hole on one side that captures the end of the cable inside the ferrule. The felt is split down one side so it slips over the cable.

Cable Ferrule

Cable Ferrule

Cable Felt

Cable Felt

I thread the handlebar end of the cable through the right control perch and attach the felt wiper as shown. The felt slides inside the cable adjuster. It keeps dirt our of the assembly and is NOT oiled nor is the brake cable as it uses an outer Teflon sheath over the braided cable.

Brake Cable Assembly at Right Control Perch

Brake Cable Assembly at Right Control Perch

Felt Inserted in Cable Adjuster Barrel

Felt Inserted in Brake Cable Adjuster Barrel

I remove the handlebar lever and flip it over and then slide the end of the brake cable inside the lever so the cable is visible in the hole for the ferrule.

Brake Cable iInserted into Brake Lever

Brake Cable iInserted into Brake Lever

I insert the ferrule into the hole in the lever with the large side of the hole in the ferrule pointing toward the end of the brake lever so the slot in the ferrule passes over the cable as the ferrule is inserted into the hole in the brake lever. I pull the cable out of the lever to seat the end of the cable into the ferrule before turning the lever over.

Inserting Brake Cable Ferrule with Large Hole Facing End of Lever

Inserting Brake Cable Ferrule with Large Hole Facing End of Lever

I twist the lever over and mount it into the slot in the right control perch. I insert the threaded pivot pin into the hole and then tighten the nut and lockwasher on the bottom of the perch.

Tightening Brake Lever Pivot Bolt

Tightening Brake Lever Pivot Bolt

Brake Lever Pivot Pin Nut & Lock Washer

Brake Lever Pivot Pin Nut & Lock Washer

I route the cable behind the upper brace and lower yoke. I insert the cable into the wire bracket using a pair of pliers to open the loop so I can slip the cable inside.

Front Brake Cable Routing

Front Brake Cable Routing

Front Brake Cable Routing

Front Brake Cable Routing

This what it looks things look like now. I’m ready to install the lower end of the brake cable in the brake lever arms and adjust the brakes.

Ready to Install Lower End of Front Brake Cable in Brake Arms

Ready to Install Lower End of Front Brake Cable in Brake Lever Arms

Adjust Front Brakes

I start with adjusting the brake cable adjuster barrel on the control perch all the way into the control perch so I have maximum slack in the outer sheath.

Part way up from the other end of the cable near the rubber boot is where the sheath ends. The sheath mounts in the rear brake lever ferrule. The ferrule has a cut in the bottom to slip over the braided cable and a larger hole to capture the sheath in the ferrule.

How Ferrule Fits on Cable

How Ferrule Fits on Cable

Inserting Ferrule in Rear Brake Lever to Capture Outer Sleeve of the Cable

Inserting Ferrule in Rear Brake Lever to Capture Outer Sleeve of the Cable

At the other end, the cable has a threaded sleeve with an adjusting nut on the end.

End of Brake Cable with Adjusting Rod and Nut

End of Brake Cable with Adjusting Rod and Nut

I remove the adjusting nut and thread the cable into the other ferrule in the front brake lever. The threaded sleeve has a flat on one end so I can hold it with a small crescent wrench as I tighten the adjusting nut onto the end.

Flats on Adjusting Rod

Flats on Adjusting Rod

To get enough slack so the sleeve sticks out far enough from the front brake arm ferrule to let me thread the adjuster nut, I push the rear brake lever forward with my left hand and then thread the nut a couple turns with my right.

Threading End Nut on Adjusting Rod

Threading End Nut on Adjusting Rod

Then I tighten up the nut using a crescent wrench to hold the threaded sleeve while I use a 10 mm socket on the adjusting nut.

Adjusting Lower Cable

Adjusting Lower Cable

I tighten the adjusting nut until the rear shoe starts to touch the drum and then back the adjusting nut off a turn. I loosen the 13 mm nut on the cam adjusting screw. I pull the brake lever at the handle bar until the front shoe just touches the drum. Then I turn the screw with an Allen wrench counter-clockwise until it stops. Then I turn it clockwise a small amount and set the lock nut.

Adjusting Brake Cam for 4 mm Slack in Front Brake Lever

Adjusting Brake Cam for 4 mm Slack in Front Brake Lever

Now I check the movement of the brake arms as I pull the brake lever at the handlebar. I want the rear brake lever to move, stop and then the front lever move. The distance each lever moves should be about equal and about 4 mm. I adjust the adjuster nut to change the movement of the rear brake lever and the cam adjuster to change the movement of the front brake lever. When the brake arms are moving equally I tighten the brake cable adjusting barrel at the handlebar (turn the barrel so it extends from the control perch) so there is about 1/8 inch movement of the lever before the rear shoe touches the drum. I get a solid locked up brake when the handlebar lever is about 1/2 way to the handlebar. When I release the handlebar lever the brake shoes aren’t dragging on the drums and the front wheel spins freely.

Brakes Are Solid at 1/2 Distance to Handlebar

Brakes Are Solid at 1/2 Distance to Handlebar

That does it for now. I’ll tweak the brake adjustments when I get the bike on the road again.

Revisions

2017-03-31 Corrected error in location of brake torque arm.

18 thoughts on “34 BMW 1973 R75/5 Install Front Brakes

  1. Would you mind putting a mark on the pics of the shoes to show the difference? I can’t for the life of me see where they are different on the pic! Also full props to BMWScotter, a top bloke and an excellent tool he has made.

    • Hi spokenoise,

      Hmm … The one on the top of the picture is the top shoe and the one on the bottom of the picture is the bottom shoe. If you look at the right side of the shoes, you will see a difference between the top shop’s right side and the bottom shoe’s right side. The right side of the bottom shoe is vertical, but the right side of the top shoe is curved.

      Scott made a really nice aid. It really takes the guess work out of it.

      Best.
      Brook.

      • Okay. I found my mistake and have edited the pictures and text. The top and bottom shoes for the front brake are THE SAME. The rear brake shoes have DIFFERENT top and bottom shoes with different shapes.

        Sorry about the confusion. At least you can’t install the front brake shoes “backwards” 🙂

        Best.
        Brook.

  2. Pingback: 1973 BMW R75/5 Rebuild: Install Front Brakes | Motorcycles & Other Musings

  3. Thanks, I have learned a lot reading through your site. New shoes are on the way and I will let you know how this all works out. Did not realize that the shoes were adjusted independently front and rear. Makes sense now!
    Regards,
    MAX

    • Hi Jeff,

      I’m glad this write-up helped you out. I had to work my way through the adjustment myself and then I got the fact that the rear lever with the weaker spring pulls the top shoe into the drum first and then the front lever pulls the stronger spring so the bottom shoe is applied. I think this makes the bakes a bit more progressive when applied.

      Best of success installing the new shoes and adjusting the brakes.

      Best.
      Brook.

  4. Just wanted to say thanks for this extensive information you’ve put up. Incredibly helpful! That wire bracket, did you make it yourself or is it available for purchase somewhere? Can’t seem to find it…

  5. Hi Brook,
    Thanks for your extensive and detailed information from start to finish. I’m following in your footsteps and getting my R75/5 back on the road after having being parked in the garage for 15 years. I downloaded the template from this site but it was about 90% too small to use.
    Thank you,
    Kind Regards,
    Mark (from Sydney, Australia)

    • Hi Mark,

      Hmm … I was pretty sure I had loaded the correct template from Scott. I found one that was too small and then found one that was correct. I’ll check again to be sure the file I have is the full size one and not a pdf of a Xerox of the original pdf.

      Best.
      Brook.

    • I also had this issue. Even went to local copy place to see if they could enlarge it. Tried 6%, 7%, and 10% larger than the PDF I printed off and none of them worked.

      I’d be happy to pay postage for a photocopy of the one you used.

  6. Thanks for this awesome tutorial! One question – is there a spacer or washer before that goes on the axle, between, the front Brake Carrier/drum and the lower fork?

  7. Pingback: Anonymous

  8. Hi, now assembling the front brake and as usual your detailed instructions take most of the problems out of the procedure. Just a minor comment, I know you drive your vehicles on the right across the pond but I don’t think Herman the German made different front forks for us ‘limies’ my brake torque arm fits on the right slider, lol.

    Back to the bike.

    Regards

    Dave

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