Profile hub bearing size?

On it lets you choose between 6203-3/4-2RS (OD 40mm) and 99R12 (OD 1-5/8 inch). What’s the difference and what’s the best one to get? I’m getting a frame built for me.


Both have an inner diameter of 19mm. The outer diameter is different. As far as I know the bearings are identical otherwise. The Yuni frame has bearing holders that match the 40mm bearing. I suppose that you’d have to choose which size bearing holders you want your frame builder to put on.

if you look at the specs on for various frames, you’ll see that bearing size dosent realy seem to relate to anything in particular except the whim of the designer. some are 40mm od some are 35mm od and some are 1-5/8"

40mm is probably most common

if you change frames later then you’ll need new bearing if the new frame has a diferent bearing holder size.

if you could get two sets of replacement nimbus/yuni/semxl/united(main cap)/dm ringmaster, syle bearing holders (there all much the same.)
then that’d make you’re frame builders job easier and consequently cheaper
because one set could just be welded to the bottom of the forks

you may be able to get bearing holders from engineering supply companies which may be better than the yuni style bearing holders.

you’ll also have to make a desicion about what size of seat post you want.
miyata seatposts only come in 22mm, (except the new gb seatposts) which you’d have to get from the usa.
but rail type seatposts don’t generaly come in 22mm. and you’d need a rail adapter too (also from the usa)

designing a unicycle with no parts from the usa is an interesting problem