I’ve been looking into getting some brakes for my nimbus 29er, do you have to drill/weld the frame to attach them?
Does your nimbus frame have brake mounts? there have been many nimbus 29" frames over the years, some do, some don’t. A brake boss will be a lump of metal on the frame leg level with the rim of the wheel, with atleast one bolt hole in it. If you don’t have them then you will need to get some brazed on, which is a bit tricky. Some people have rigged various stuff without modifying their frames, I’m sure they’ll chip in here.
You could fit a BMX caliper brake pretty easily - only needs one hole drilled through the crown. Should clear most 29er tyres I think, but if you’re running a really big one it might be a bit close (there’s plenty of clearance with a 2 1/4" 36er tyre, so should be fine with 2.1" or 2.3" 29er tyres).
My frame doesn’t have any brake mounts, and i really don’t want to do anything permanent to it…is that possible?
I have a Nimbus II 29’er that has a v-brake mounted. I used a v-brake adaptor and strapped it on with hose clamps originally, and now it is mounted with a bolt through a single hole in the fork crown/seat tube.
You can see pictures of the uni here and you should be able to see the straps holding it to the frame. Originally I had a 26" wheel in the frame and the brake had to be much lower than the drilled position would allow. The braking is no better or worse now than when it was strapped on.