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Improving ATE Disk Brakes

Improving ATE Disk Brakes

Tom Childers

I was never able to get satisfactory brake feel with the stock cable-operated master cylinder on either my R90/6 or my R100. Braided-steel brake lines are a big help, however, there is an even better alternative...

For $250 to 300, you can convert dual ATE brakes to use a bar-mounted master cylinder with braided brake lines. I completed this conversion for my '79 R100S in 1997, and as of 2005, all the parts are still easily available. Note that you can probably still get a kit from CC Products in San Jose, California that does a similar conversion, but it will cost more, and will not give you quite as good results, because the brake lines are longer and go through a T-adapter.

Here are the parts you need to do this yourself for 1975-79 R-bikes with single or dual ATE brakes (1974 support is unknown; someone told me that the 1974 R90S had some type of difference that prevented this specific conversion from working):

The conversion is pretty straightforward, and takes about 2 hours, with beer breaks, if you have all the parts:

  1. Disconnect the fuel lines and remove the tank. Disconnect the lower end of the brake lines, and drain them carefully. Take the lid off the master cylinder, so it drains too.

  2. Screw the brake cable adjuster in on the left handlebar, unhook the cable, then screw the adjuster all the way out to disconnect the cable.

  3. Put the cap back on the master cylinder. Unplug the electrical connectors from the brake switch on the master cylinder, then carefully remove the old master cylinder and old brakes lines completely. Use rags rubber-banded over the ends of the brake lines to keep brake fluid from dripping out.

  4. Remove the throttle cam cover on the right grip assembly, disconnect the throttle cables, disconnect the switch cluster, and remove the old right grip assembly.

  5. Loosely mount the braided lines to the new master cylinder assembly with the double banjo bolt and with copper washers in between the brake line terminators, and mount the assembly on the handlebar. Position the lines to run between the forks in front of the upper triple clamp, and behind the lower triple clamp. Tighten the banjo bolt with the lines in place, once you are sure that they will clear everything as you turn the fork from lock to lock.

  6. Install the throttle cam with grease, reconnect the throttle cables, install the throttle grip with the correct cam alignment and more grease, and screw the throttle cam cover on. Extra hands may be helpful :-)

  7. Replace the brake line grommets, and attach the brake lines.

  8. Install the new throttle switch, route the wire down behind the head tube, and plug the male spade connectors into the original brake switch female spade connectors. Zip-tie the wires in place, making sure they don't bind as you turn the fork from lock to lock. With the ignition on, make sure the switch is activating the rear brake light.

  9. Fill the master cylinder and bleed the system. You will probably also need to re-synchronize the carbs.

It is amazing how much better the ATE brakes feel with a handlebar-mounted master cylinder and steel lines. With good soft pads, the front brakes work very well and are up to modern performance standards.

Kudos to Colleen Bray now at Bob's BMW in Maryland, and Bob Schenker in Oakland, CA, for helping me put this together. It was Bob's pioneer work with his 1981 R100S brakes that convinced me to do this.