Amount of rim flex under normal riding? How much space do rim-brake users leave?

[brycer1968]

@magnustudios

I’ll try to start a proper thread for my current project soon (project), but right now I have one specific question that will help me move forward on it: How much does a well-built 36" wheel wobble within the frame under normal use? I’ve read people mentioning rubbing their rim on the brakes on hill climbs… how much of a gap is normally left for these brakes?

I need to mount two optical sensors as close to my rim as possible, but I’d like to minimize the risk of damaging them. My unicycle is broken at the moment so I can’t measure it myself, and I figured with all the brake users someone should be able to give me a good ballpark. How close can I go?

Interesting project.
I’m with the others on here, assuming your wheel is well built and tensioned, its likely frame flex that makes the pads rub at idle and on hard acceleration, but the KH frame probably flexes the least of all the 36er frames out there.
I run a hybrid HS33/HS22 “frankenbrake” on my single speed KH36 that lets me set the brake pads back further from the rim than the stock HS33 will allow. THis is more on this set-up: HS33 / HS22 Magura unicycle brakes

I just measured the clearances between both sides of my KH36er Airfoil rim and brake pads with a dial gauge: looks like about 5 mm of clearance per side. Set this far out, the pads don’t rub (I’m 200 lb road/distance rider with moderate skills and speed).

Hope that helps a bit.

Brycer