Replace Nexus 3 with rollerbrake with Alfine 11 I have a cargo bike equipped with a Nexus 3 hub shifter and related roller brake. Since where I live is pretty hilly, I'd like to replace it with a shifter with a big range and little gap between the gears, as the 11 speed Alfine hub shifter. Unfortunately, the Alfine is available only in disk version, while my bike doesn't have mounts for disk or v-brakes. Moreover, the bicycle has poor braking performance when fully loaded, so a disk brake would be a valuable addition.



Is there any adapter I can use to mount a disk brake caliper on the rollerbrake mount?
Are there chances that the bike present clearance problems while trying to mount a disk brake on it?

Update: In the end I mounted a Nexus 8 shifter with its own brake. The rollerbrake sold with the nexus 8 is the one with heatsink fins and, after some months of use, I can say it offers a lot more braking force than the one that comes with Nexus 3. The braking performance of the rear wheel is now comparable with a good disk brake (with less, but overall sufficient modulation). Adding the proper braking grease increase the modulation. I can warmly recommend this setup to anyone has similar constraints.
I think your next point of call will be to speak with a framebuilder local to you.  The chainstay has the big tab for your roller brake, so the chainstay is beefy enough for that.  Whether that translates to being enough for a disk brake, I can't say.

What you need is a pair of brake mounts brazed onto the bare metal, and perhaps a brace up to the seat stay to spread the load.  Once welded in it needs painting too.

If you go this route, consider what else you might want done to the bare frame.  Do you need additional mounts for racks, bottle cages, brake lines, etc?  If so, get them all done by the frame builder in one visit.  You generally have to strip your frame completely for work like this.



Does your fork have a disk brake mount?  If your bike has front suspension, its even more work to weld/braze because of the suspension.  If you have a rigid front fork, see what your frame builder says. but often the front tines are too weak to take a disk brake and you have to buy a stronger fork anyway.   However if the frame builder's got a painter, you might want them to paint your welds and the new fork so they all match.