Seems all my bikes are being blighted by brake issues. While the Ducati has reassuringly unpredictable electrical problems, the BMW has reassuringly German, old-fashioned mechanical problems.

So the symptoms were pretty simple. The rear brake jams on after a few miles of riding. Just happened out of the blue while commuting to work one day. Being a bit of a MacGyver type, I got my house key out and wiggled the brake pads back a bit. Wasn’t easy, especially as the brake was red hot from the friction. Took 10 minutes but it seemed to work eventually.

The rod that the pads slide along looked rusty so I assumed the winter road salt had done its worst. Same happened on the way home. So back at home, I stripped the brake caliper, regreased with copper grease and reassembled. Same happened the next day so that didn’t work! BTW. The rear caliper isn’t actually bolted to the swingarm. It sits on a free-floating ‘peg’ on the swingarm and is simply held in place by the brake disc running between the pads. So if you’re looking for the bolts to remove the rear caliper, you won’t find any. Just remove the rear wheel and the caliper falls off by itself.

I also adjusted the push-rod that connects to the Brembo master cylinder from the rear brake pedal. Same issue happened. I even took it off, bled all the brake fluid. Disassembled the Brembo cylinder, greased the internals checked the spring blah, blah… no joy. TIP. If you need to bleed the brake fluid and you have the ABS model, you need to rotate the rear wheel to push the fluid through. Took me ages before I realised.

As usual, online forums were full of confusing advice, as they were solving someone else’s problem, not mine. I have the ABS version, so lots of chat about the ABS sensor having issues.

Cutting to the chase, it WAS the Brembo master cylinder, but it needed a new one to solve the problem (or a rebuild kit I guess). It was as simple as the piston not quite returning to the resting position. The image above shows the ‘sticking’ one on the right and you can see the black piston is 5mm or so lower than the new one on the left. Therefore the brake fluid was being ‘pushed’ by the lever, but then being held there. The pads then stuck on, causing friction against the disc, causing heat, making the fluid expand, binding the pads even tighter. Explains why it took me 10 minutes of ‘fiddling’ that first morning before the brake worked again. It was the fluid cooling down and releasing the pads all by itself.

So I ordered a new master cylinder (they’re fitted to loads of bike models). Making sure I had the ‘in-line exit’ version (as the fluid came in from the side and out from the top… in-line with the body) and the slightly bigger piston version (13mm rather than 11mm) for more oomph. It’s part number 10.4776.60 so google “Brembo 10.4776.60″ and you should find one. I got one from this page on IntoBikes.co.uk for £43. Putting the old and new one side-by-side, it was immediately obvious the piston (the white ceramic looking thing) wasn’t returning to the starting position against the circlip/washer like the new one did.

Bolted it on, new fluid (making sure to pump it through by rotating the rear wheel). Problem solved! Been riding it for 2 months, no sign of any problem.

There was some chat online about needing a special tool to bleed the ABS internals as air bubbles would cause it to malfunction, but I didn’t have any problems. Tried it out a few times and works fine.

So, as usual, bodged my way to another fix. Hope that helps if you were having similar problems!

Notice that the pivot bolt that sticks out of the back of brake on the left is very short as it’s designed to go through a small rear chainstay, not a chunky fork. One solution is to replace the pivot bolt with a longer one but these aren’t available for the Kurve brakes (they are available for some Shimano brakes though). Another solution is to use a longer recessed bolt to bridge the gap. I’ve had to use a super-long 30mm recessed bolt just to attach a normal front brake, so I’d need at least a 50-60mm recessed bolt… and these don’t exist.

So my solution was to make one. I thought I’d share the process just in case it helps you out of a sticky situation too.

First, this is what happens in a normal front fork…

Now this is what happens when you use a rear brake with short pivot bolt… it doesn’t work!

Even using an ultr long recessed bolt doesn’t work…

So I need to make a longer bolt somehow. I’m also keen to keep the ‘recessed’ bolt feature, as it’s not only neater but is how the fork was designed to accommodate a brake bolt. I could try and surface mount a bolt but this may end up damaging the carbon fork’s outer shell. So you’re going to need some kit…

So first thing to measure stuff. Insert the brake into the front of the fork and hold it in place. Insert a spare bolt or allen key into the rear of the fork until it comes into contact with the brake pivot bolt. Make a mark on the allen key where it exits the back of the fork. If your fork has a recess (like mine) then mark where the allen key first exits the fork, niot where it finally emerges from the recess itself. Obviously, this is how far in the pivot bolt is inside the fork, or to put it another way, how long a custom recessed bolt shaft would have to be to just touch the brake pivot bolt but not screw onto it. Mine was about 40mm. Now add 10mm to this measurement to allow for a good overlap with the pivot bolt when it’s screwed in. I.e. now a total of 50mm.

So now we need to get some recessed bolts to use as parts. Seeing as my fork seems to be very wide, I got hold of two 30mm recessed bolts from my local bike shop. I’m a “known person” so I got them for free but expect to pay about £3 each. Put it this way, there’s a 35mm titanium one for $7 Toronto Cycles or a 30mm steel one at SJS Cycles for £6.99.

So I need to make a bolt 50mm long so I can do that with a 20mm recessed bolt and 20mm of the threaded tube from the other bolt. So next thing to do is to use a hacksaw to chop 20mm off the threaded tube part of the long recessed bolt. File it as flat as possible and offer up the ‘unchopped’ end to the end of the existing recessed bolt, so you have a nice, clean interface between them. Now we need a way of joining them together…

You’ll also need to chop the threaded bit off the normal bolt. Again, measure it so that it’s long enough to fit entirely within the normal recessed bolt and has enough extra thread to screw into the threaded tube… but short enough to leave that 10mm or so of the threaded tube free at the end. Use s file to flatten the end of the bolt and remove any rough metal. Then carefully cut a slot about 3mm deep into the end with a hacksaw. It doesn’t have to be too neat but it does pay to be as accurate as you can. That’s it for the manual labour.

Now add some strong metal adhesive / epoxy glue (I used Araldite Rapid Steel) to the threaded shaft and screw it into the normal recessed bolt. Be sure to clean the thready first mind as any grease will stop the glue holding. Use a flat headed screwdriver in the slot you cut to tighten it. Then screw on the threaded tube to  the rest of the shat that sticks out (again, with glue). Leave to set for at least 24 hours (or whatever your glue instructions suggest.)

Now you should be ready to rumble. If all goes well and you have measured everything relatively well, it should just work like a normal recessed bolt, only a really long one! Thus…

Finally, don’t forget to swap over the brake pads as they are directional and because you’ve flipped the brake, the left pad will now be on the right and vice versa.

Now there’s no excuse not to use all those rear brakes cluttering up Ebay!