BMW tips galore!

I’m a new-ish subscriber to CBG, as it seems to fit my current interests better than another classic motorcycle mag I’ve been reading for 40 years. Like you, I have a 1978 R100RS in my garage – mine is the Motorsport Limited Edition (which seems to be just a white paint job with Martini pin-stripes). Anyway, it appears that you may be coming towards the stage of setting up the front brakes, which is my reason for writing. Under “special tools” you will need a stick of chalk. The front brake calipers on our machines are mounted on an eccentric pivot, which alters the angle of the face of the static brake pad to the disc. For optimum braking, one needs to have the pad contacting the disc across the entire face of the pad. When the brakes have been installed, mark a chalk line radially across a disc, gently apply the brake so that the wheel will just move, and turn the front wheel one revolution (by hand or push the bike forward). If the chalk line disappears entirely, then miraculously you have achieved the optimum set-up instantly.

It is more likely that only part of the chalk line was rubbed off, so adjust the caliper spindle and repeat. This can provide hours of fun until you are satisfied, and then you have the other side to do.

Amusement could also be had from watching the rubber brake lines expand when the front brake was applied hard – self-limiting the amount of braking force that could be applied. Perhaps this was a safety device to prevent the front wheel from locking up. A set of Venhill braided hoses on my machine removed this source of amusement and improved braking.

Disc brakes in the 1970s were notorious for not working well in the wet. BMW’s answer seems to have been to use a sintered-metal pad, which worked as well as anything else as a brake, but also machined a groove into the face of the discs so that within about 45,000 miles, the discs were scrap. They can be faced on a lathe, but not by much and I found that the grooves took the discs below minimum thickness. I got a good secondhand pair from Jamie Sherlock around 1983. Hope this helps with the reassembly, and I look forward to future articles in the series. Best wishes,

Tom Poole

Dear Tom, many thanks to yourself and others who have offered advice for my BMW project – I was not looking forward to the brake adjustments! Discs only lasting 45,000 miles? I’m happy with that… Venhill are on the list, but am wondering whether to have a long one-piece hose to replace the solid lines or not. Matt