Different sized wheel on a Nimbus frame

I have a 26inch nimbus oracle muni.

Can you fit a (nondisc) 20inch wheel for trials etc.

Any thoughts would be gratefully recieved.


Yes you can. Will look a little bit ridiculous and maybe you’ll hit your knees on the frame, but technically it’s no Problem

The oracle has a internal disc, right? I am not sure how far the brake caliper is showing inside the wheel. You should check the clearance, as the 20 inch disc hub will be symetrical and left side spokes will be closer to the frame.

Also you should to put a spacer between your brake pads when not using the disc wheel. Otherwise you will have to push them back if you acidently hit the brake lever without a disc inside.

Another material issue I see is the seat post.
Maybe it won’t fit both.
lets imagine the seat post tube is cut so that on the 26er config you can not put it deeper in the frame (at least for a kh frame where there is a dead end)
When you will put the 19er wheel, you will have to put the seat post deeper inside the frame tube if you want to keep the same “saddle-top-to-low-pedal distance”, and even more deeper knowing that on a trial unicycle the saddle is often set very low in comparison with a muni or a road unicycle.

Since you’re speaking about a nimbus frame, there is a hole on the bottom of the frame instead of a dead end, so you can set the seat post very deep in the frame, but it will be ugly cause it will protrude a lot!

The better solution: two seat post+ saddle sets.

If you invest in an additional wheel (including cranks and pedals) AND additional Saddle and Seatpost, then I would personally throw in the extra bucks for a 20" frame and don’t have to change wheels.

Exactly. You can get a 20" steel fork for 25 Euro and a steel seatpost for less than 10 Euro. Then a saddle of your choice and off you go.

Better having another uni than changing wheels :smiley:


It won’t make a difference because the distance from the seat to the center of the wheel is the same, no matter the size of the wheel.

It’s true that another frame is probably a good investment. And slowly you can get the parts to make a second uni. I just did something similar with the parts I had laying around: make a new uni just buying a rim and a tire, good deal.

Right. Also, trials cranks are usually ~140mm, cranks on the 26" wheel are probably longer at 150mm, so if anything you would want to move the seatpost UP to keep the same distance to the cranks.

But then you probably want a slightly lower seatpost to do trials, so you would move it back down again, and it would be a wash.

I don’t think spokes running into the brake would be an issue because they angle in much more sharply for the smaller wheel.

Thanks for info

I think I will bite the bullet and get a trials uni as well!

I am 144lb. 10st 4lb
The 19" Club ‘Flame’ Trials Unicycle is rated up to 11st has any one any experience of the lower end trials unicycles?

Thanks again.

I wouldn’t do it (the “flame”)

If you were getting it to learn to do trials type riding you would likely find the rim to be on the skinny side resulting in the tire folding at the pressures you would want to ride, especially with the light tire.

The seat sucks for sitting on, but that isn’t necessarily a big deal for trials riding.

The steel cranks aren’t likely to last long when hopping. Qu-Ax cranks would be a major upgrade and might last, while upgrading to Nimbus Venture2 cranks would likely last just fine if installed properly and maintained.

The hub UDC uses is really quite good but the square taper interface is much more prone to slopping out than ISIS or other splined interfaces available.

There is nothing wrong with the rest of the unicycle. Really it is a pretty solid learner that happens to have a trials sized tire, but not a unicycle truly designed to withstand the rigors of trials unicycling.

Looking on the UK UDC the Impact Athmos looks like a much better deal.