Fitting Brembo 4 spot calipers to R65.

[Tony Smith]

I have acquired left and right 4 spot calipers from a K bike with the intention of fitting one (or possibly both) to the R65.
 
The bolting pattern is the same as the FO8s but of course the center of the caliper misses the center of the disc by about 5mm.
 
My question is whether or not anyone here has ever fitted 4 spot calipers to their R65 - I thought I remembered a thread where this was discussed but cannot now find it.
 
Subject to somewhat more careful measurement, I propose to take 2.5mm from the caliper mounting pads and 2.5mm from the mounting pads on the fork legs - the nett result being to "move" the caliper center to the center of the disc. The idea of taking 2.5mm (approx) from both invitees to the party is to not overly structurally weaken either component and give me the capability of returning to an FO8 (using packing washers) if I ever have to.
 
My questions are:-
 
1/. Has anyone already done this?

2/. What were the actual measurements used, and finally;

3/. What diameter master cylinder did you use (I am confident that my existing 13mm Master cylinder will happily service a single 4 spot and quite possibly two of them as BMW are so conservative in hydraulic ratios.




Any input welcomed.

[John M]

Hi Tony, I fitted a single 4 pot oilhead caliper to both my 1986 R65 monoshock and my 1984 R80 ST. The R65 had a 14mm master cylinder which worked very well with the single 4 pot caliper. the 1984 r80 ST master cylinder was a 13mm size but was shot so i ordered a new 14mm master cylinder from Motobins.  I think your 13mm size would be fine for a single 4 pot caliper, however using it for 2 calipers might result in too much lever travel. The 14mm size seemed to work well with a single 4  pot caliper--- good feel and not excessive lever travel. A single 4 pot caliper is a great improvement and I feel no need for dual discs now at all.
I machined approximately 4 mm off the caliper ears to get the caliper to center over the disc with both bikes ( If my memory serves me well )

[Tony Smith]

Thanks John. Silly question perhaps - but did it work better and was it a worthwhile investment of your time?

[John M]

a very worthwhile change . Also the Galfer green pads are excellent, much better feel and braking power with just a single brembo 4 pot caliper. I see no need for dual discs with  this set up I also installed new stainless Motobins brake lines on both bikes