K1100 Brake conversion.

[Julio A.]

I just received a pair of 4 pot K1100 brembo calipers and a extra disk just for experimenting.

I have measured the calipers and they fit the R65 brake mounts and disk.
The Brake lines are also the same, It's like a simple drop in part. I have already installed the Extra disk today but have sent the calipers for overhaul to be safe. Maybe early september, when the semestral brake will come should I have enough time to work on it again.  

What do you guys think? Is it possible?

[Bob_Roller]

The master cylinder on the handle bar, may not have enough fluid movement to operate all of the pistons at the calipers, especially if you have the smaller 12 mm master cylinder.

You'll know when you get them installed .

[Julio A.]

Hmmm, I was thinking about that.

Is the 12mm master cylinder the circular or the rectangular one?

[Bob_Roller]

It can be either, there should be a number cast into the bottom of the master cylinder, should be a 12, 15, 16, that refers to the diameter of the master cylinder bore in mm .

[Julio A.]

Thanks for the heads-up, I'm still pushing through with my plans. If ever it does not work, I'm still converting it to dual disk brakes by using some spare, identical to stock K100 calipers.

[Bob_Roller]

With the addition of the right side caliper and rotor, a spacer may be necessary to place the caliper directly over the rotor .

Don't know if you will need to do this or not .

http://www.realoem.com/bmw/showparts.do?model=0364&mospid=51897&btnr=34_0598&hg=34&fg=05

It's item number 5 in the illustration .

Even though it looks like it goes into the caliper, the spacer is placed into the hole on the fork leg, the flange thickness of the spacer is what aligns the caliper on the rotor .

[Crossrodes]

Bob, re the number stamped in the "bottom" of the master sylinder... are you speaking of inside or outside the master cylinder.

[Bob_Roller]

Outside of the master cylinder .

[Crossrodes]

Thanks Bob.  

I checked it in better light today and boy am I surprised.  Mine is a 16 (I have dual ATE disks).  I'm surprised because the braking on my bike is marginal at best (Of course I'm comparing it to the Wing which stops really well even though it weighs a ton).  I had the complete system apart on the R65 for a cleaning, fluid change and stainless brake lines 2 years ago and I don't think anything is wrong.  But when I get it back together this time I think I'll do a more complete check and make sure both calipers are functioning correctly.

Also my back brake (mechanical/drum) must really grab.  I can slide my back tire with very little pressure on the back brake.  I've had it apart multi times and I'm sure it is functioning properly...I'm guessing it's just that skinny back tire that will cause it to slide so easily.

[Justin B.]

The rear drum brake gets a lot of "bad press" from the snobby types but since only about 20% of your braking happens at the back a drum is more than enough, rear disc brake is more of a marketing ploy.  BMW experimented with the rear disc (likely due to criticism in the MC press for lack of) on the early 80s R100RS and RT and went back to drum after a couple of years.