Please Help Me

My Nimbus 28" unicycle has just arrived in the post and the frame doesn’t fit the wheel tyre properly because i ordered the bigger (2.35) Big apple tyre compared to the (2.0) Big apple tyre Roger emailed me and said something about ‘shims’ ?

What are these?

By how far does it not fit? My tyre barely fits in without shims to the point that once a revolution it buzzes as it touches.

“Shims” are little bits of something put on the bearings to “jack up” the frame a bit. Thin bits of metal work well; if you have a drinks can get someone to cut it into strips and lay a few on top of each other inside the bearing holders on the frame.

This picture shows two sets of bearings, one with a metal strip around it to act as a shim, and one without.



You could probably use some strips cut from a tin can as shims to raise the frame. Put the tin can strips in the upper bearing holder on the frame. You may need to get longer bolts for the bearing holders after shimming it up like that. And you’ll need tin snips to be able to cut the tin can. If you can find a tin can with a small diameter (about the diameter of the bearing) you’ll be off to a good start.

Aluminium drink cans can also be used for shim material, but aluminium drink cans are very thin and won’t make good shim material for this application. You’re going to want a more sturdy material like a tin can.

You’re only going to need to shim up the top half of the bearing to raise the frame. The shims that Phil showed go all the way around the bearing which is not necessary for this case.

Hi Treepotato,

I am guessing you are running the rounded crown frame with Nimbus 2.35? If so that is the same combination as me. You are probably finding it is missing by only a small margin?

I have done two things, firstly made some shims, and then filed the frame where the tyre would have rubbed to give slightly more clearance (for when little stones stick in the tread off road).

Firstly the shims, I found some Aluminum sheet in the shed, which is ~1.8mm thick. I cut them into 50mm12mm1.8mm, these can easily be bent around the bearings with finger pressure (atleast enough to mount them into the frame). Aa already mentioned a few sheets of baked bean tins would also do the job. I have not had to change the bolts.

I have enough Aluminum to make about another 5 shims, if you want I could cut some up and put them in the post, you’d hopefully get them Wednesday.

If you want me to post a couple of shims let me know on this thread and mail me your details privately to keg -at- unicyclist -dt-com. If you want to check up on me first before giving your details ask Sarah @ Exeter, she has known me for a few years.


Re-read Phil’s comments, although his only just rubbed my frame was much worse. You could rock the bearings inside the holders noticably, no chance of fitting the bottom holders and spinning an inflated tyre.

Remember it will be great once it is sorted. Currently I much prefer riding my 29" on road and especially in the woods compared to the Coker, this was not what I expected.


Thankyou very much for your help and tips everyone,

panic over because my brother (he’s good with bikes and fixing stuff) came home and he helped me put my uni together and once he’d tightened it and stuff carefully its ok just need to cut the seatpost because its massive at the moment, its brilliant that i know that if i post a message asking for help people are always really helpful thankyou :slight_smile: