Another: Brake master cylinder question.

I was going to link on to Bubbs post, But he's closed it, so I've started another one in a similar vain.

I have aquired a pair of Leading link forks for my 1989 R80 Mono (ex RT) outfit. A very nice set from Wasp.


The LLs came with a pair of K1100 four pot callipers and I'm wondering two things.

1, My R80 has a single front disc and standard Brembo calliper. If I where to fit the twin 4 potters, What size master cylinder would be recomended?

2, I also have a pair (separate from the fitted single) of the Brembo callipers. Which is the correct size master cylinder for these and would the 4 potters be that much better?


Machining the 4 potters:
My wife Jill has a 4 pot caliper on her 100GS, which came on the bike. I know it has been machined to get it in the correct line and comparing it to the new ones it looks like (as I haven't taken it off to measure it propperly) it's been machined from 15mm to 11mm. Is it the same for the RT as the GS?




Val.

Val
For information
In upgraded the brakes on my GS from single 2 pot Brembo to single 4 pot Brembo (K1100 callipers) and then to twin 4 pot (K1100 callipers}
I used the fitment for R100R Paralever fitted with 4 pot Brembo, as the brake set up was the same eg. K series type master cylinder 4 pot Brembo the master cylinder diameter listed on the BMW parts fiche are listed below
Single disc - master cylinder = 13mm
Twin disc - master cylinder = 15mm

The master cylinder on my previous K1100 whit the 4 pot Brembo's was 20mm diameter

I have the 15 mm fitted to my GS and it works well, but as your bike has the older style master cylinder its only showing a 13 or 14mm master cylinder option

Regards
Colin

https://www.motobins.co.uk/
Moto bins list master cyl from 12 through to 16mm

Try again
https://www.motobins.co.uk/
Edit,can’t get the page to embed.
Look up
R100rs 85 to 96

Thanks guys, Gives me an idea of where I want to go with all this extra braking ability. Will be getting the outfit in the garage in March to get it fitted with the LLs and the new callipers. I'm crossing my fingers the K yokes will be a straigt fit.

Mikeyboy, Cheers for the Motobins link. I found my way there eventualy. A bit supprised though to see a £30+ difference between theirs and Motorworks prices for new MCs.
Now I have the LL's I probably won't go so far down the route of giving the bikes the suspension lift we talked about.

mikeyboy said:

https://www.motobins.co.uk/
Moto bins list master cyl from 12 through to 16mm

Click to expand...

graham_cj said:

Val
For information
In upgraded the brakes on my GS from single 2 pot Brembo to single 4 pot Brembo (K1100 callipers) and then to twin 4 pot (K1100 callipers}
I used the fitment for R100R Paralever fitted with 4 pot Brembo, as the brake set up was the same eg. K series type master cylinder 4 pot Brembo the master cylinder diameter listed on the BMW parts fiche are listed below
Single disc - master cylinder = 13mm
Twin disc - master cylinder = 15mm

The master cylinder on my previous K1100 whit the 4 pot Brembo's was 20mm diameter

I have the 15 mm fitted to my GS and it works well, but as your bike has the older style master cylinder its only showing a 13 or 14mm master cylinder option

Regards
Colin

Click to expand...