It happened! Finally!
Took ages because I was not crazy about using a Magura Louise or Clara since those are essentially bending the disc towards the non-piston side of the caliper. I sourced a Magura Gustav brake on eBay - those are still popular among downhill MTB riders and are surprisingly expensive for a 10 years piece of kit. The Gustav is also a caliper with a non-piston side like its contemporary friends but it has two pistons on the other side. And the whole caliper is mounted on what Magura calls a ‘hanger’ on which it can slide sideways. Basically it’s a floating caliper, a technology used in cars and motorbikes for decades before opposite pistons became the norm.
I learnt about the details of this brake the hard way: the one I bought was surprisingly cheap… because it didn’t have the hanger. It took ages to source the right one (Magura offered 11 different models at one point!) and at a reasonable cost. Special thanks to Magura USA (not DE…) for pointing me in the right direction.
Here is the hanger - fork is upside down. I had to grind it a bit as it was too close to the rotor. The rotor is very close to the fork, more than usual.
The caliper in place - again, fork is upside-down:
And with the wheel in place. You can see how narrow it is on the spoke side of the rotor. The nice thing is I could go back and re-lace the wheel with the spokes in a more usual 3 way crossing. I guess it’s still popular with downhill riders as it lets you build a stronger wheel with not much dishing unlike modern calipers - Magura also offered a Gustav hub back in the days:
Ok, all in place now:
And the whole beast:
I still have to optimise the angle the caliper makes with the rotor with .2mm washers which should arrive by the end of the week. Magura’s literature claims there will be a constant rub noise but no actual rub: “the wheel can spin 10 rotations without stopping”. In my case, the angle is partly due to the frame not being super straight. An issue I had with my KH frames and which is also present on the Mad4One frame. I check the wheel in a truing stand, and it’s perfectly aligned…
I’ll need to make some kind of KH starfighter/spooner thingy to have a better grab of the brake handle. I have some spare L shape trim which should do the trick.
This build went on for ages but I’m happy I took that challenge. I’ve been wanting to put the Schlumpf in a 32" wheel - except there is no way to have rim brakes on those - so now I know I can do it. And in theory, the 32" wheel will fit just perfectly in this Mad4one frame…
Thanks again for Lobbybopster for sending me down the rabbit hole of Schlumpf disc brakes! It’s been fun and a learning experience.
(ok now I have to go try the thing, but the weather hasn’t cooperated lately)