Rear brake fluid reservoir cap question

AntonLargiader · Jun 4, 2021

The under-tank MC had the float system because the brake fluid level was not able to be checked with a normal visual inspection. When the MC went to the handlebar you could see the level and no longer needed the light. I'm not sure why the rear ever had a float; maybe just because BMW already had the warning system in place and couldn't resist the chance to extend its use. But if you can see the fluid level, you don't need the float.

ezwicky · Jun 4, 2021

Thanks Anton, that makes sense. I'll just use it as-is, since it's sound in every other way.

stevenrankin · Jun 4, 2021

Who knows

Anton, we will never know why BMW did things they did. My 78 RS has a rear master cylinder with the float and wiring tied into the warning light on the dash. Either the front or the rear low level will light the light.

It was a short span of years they used a hydraulic rear brake with the float and switch. The early 77 RS bikes had drum rear brakes as did the /7 bikes, Then in 78 the RS went to disc, followed in 79 by the new RT. As for the 78 and newer /7 bikes and the S bikes it is fuzzy on when or if discs were used or drum. Oh, the S bikes used disc, not sure if drum was used all years of the /7 bikes.

All I know is 80 and 81 was the cross over for changes in the bikes for brakes and ignition systems. Kurt and Snowbum, LOL keep better track of things than I do. St.

lkchris · Jun 4, 2021

STEVENRANKIN said:
Anton, we will never know why BMW did things they did. My 78 RS has a rear master cylinder with the float and wiring tied into the warning light on the dash. Either the front or the rear low level will light the light.

It was a short span of years they used a hydraulic rear brake with the float and switch. The early 77 RS bikes had drum rear brakes as did the /7 bikes, Then in 78 the RS went to disc, followed in 79 by the new RT. As for the 78 and newer /7 bikes and the S bikes it is fuzzy on when or if discs were used or drum. Oh, the S bikes used disc, not sure if drum was used all years of the /7 bikes.

All I know is 80 and 81 was the cross over for changes in the bikes for brakes and ignition systems. Kurt and Snowbum, LOL keep better track of things than I do. St.

BMW was unique in having an under tank brake fluid reservoir and since you couldn't readily see the fluid level, they provided a fluid level warning capability. When they went to the handlebar reservoir, the fluid level was easily visible and no level warning was necessary. The rear level warning never was necessary, but the circuitry was there so they did it.

BMW is massively safety conscious and since it is essentially a family owned company they are extra conservative regarding their liability. Motorcycles are "dangerous!"

Rear brake fluid reservoir cap question

AntonLargiader

Active member

ezwicky

Member

stevenrankin

Active member

lkchris

Active member

Similar threads

Forum statistics

Share this page