[Newbie] Tires, Rims, and Sizing Questions

First off let me preface this with a disclaimer, I am rather new and don’t know much about unicycling, nor do I have much experience with bikes and as such I hope these questions aren’t too stupid :stuck_out_tongue:

First off, a little info, I have a Nimbus II 24" Freestyle with a Kenda somethingorother 2.10 inch.

I was thinking about sticking a
for more control in the dirt. This got me thinking about things outside my knowledge range, like, “If I were to stick a larger tire on my uni, at what point would I have to change the rim?” How much larger a tire can you get before having to buy a wider rim?

“If I get a wider tire, how much does that affect the height of the tire?” The Nimbus II Freestyle frame doesn’t have much space inbetween the frame and the tire, just less than a quarter inch, and I don’t wish to buy a tire that is too tall.

My tire has a quarter of an inch and change on both sides, could I up the size of the tire to a 2.5 and be fine with less than a quarter inch overall extra space? And if this works, would there be any issues with mud caking the sides and maybe rubbing?

Edit: I remember hearing someone say that for a uni, you need a tire with a rounded tread so you can control it, can anyone elaborate on this?

Any assistance would be appreciated!


The rim on those Nimbus unis is 32mm wide. It should work for any tire that will fit the frame. I use the same width rim with a 2.5" tire without any trouble. There is some fold over if I’m hopping with really low tire pressure, but it hasn’t been a problem.

This I’m not sure about. Those freestyle frames are narrow compared to munis. You can get a K-Rad in 2.1" size. That would be a safer option. If you ride in mud, you do want some clearance between the tire and the frame. Even if a 2.3" will fit it won’t leave any extra space. Is it out of the question to buy a muni frame?

Some tires have a more square cross section. This is ok on flat surfaces, but if the path is slanted to the side, the square profile can pull the whole uni sideways as well. I’ve noticed this on my 36" uni since the tire is starting to get worn in the middle. I feel the road crown more than I used to when the tire had a more round profile.

I’ve never experienced this, but I’ve heard people complain about tires that have tread that makes a tall ridge in the middle. On flat surfaces, it always wants to lean to one side of the ridge or the other. It’s another thing to keep in mind.

I have about .3" on either side of the tire as it is right now, could I take that down to .1 or is that too small? A 2.3" tire would leave about .2" on either side I believe. This unicycle used to come with the Maxxis Hookworm which I believe was a 2.5", but I am unsure about the vertical profile of it.

Unfortunately, I have no money I can spend a MUni frame, but am saving for a Nimbus Drak.

Has anyone on here actually used the K-Rad, and is it actually aggressive enough that the tread won’t fill up with mud the first time I take it out when it’s wet?


It depends how much mud you anticipate riding in. That would be rubbish here in the UK, but probably OK in California (over here bikes tend to be described as “designed in California” if they don’t have much clearance). Though I should point out that the worst mud for clogging up I’ve ever ridden in was in Utah which most people - at least people in the UK - would expect to be dry. I don’t have a good idea what Virginia is like in that respect.

I also feel the need to point out that right now in the UK you need about an inch of mud clearance :frowning:

It’s been rather wet here lately, but I won’t ever be riding in deep mud, more like the dirt is wet and clingy and fills up the tread.

I rode in the super sloppy mud today and with a inch on all sides my wheel clogged up

I know someone in Cincinnati, and they said the weather was less than beautiful…

Does it actually clog up the tire between the tire and forks? If it does, why doesn’t it sling off?

Some mud is stickier, and some tires shed better than others. If you are in sticky mud, and have a tire that loads up easily it could bind quickly.

Disclaimer: This is true. The Hookworm did used to come on the Nimbus II freestyle, however they have changed frames or something, and newer ones I believe will not fit the hookworm. I received a Nimbus II for Christmas of last year, and really can’t imagine putting anything bigger than a 2.3" tire in it. The 2.1" NPJ that it comes already fills the frame pretty well.

Thank you, I did not realize they had changed the frame design. The NPJ does fill the frame rather well but I simply thought that it might be a normal thing to have a larger tire than the stock tire squeeze into the frame rather snuggly.

Maxxis discontinued the 24" Hookworm due to poor sales. The current description for a new Nimbus II 24" Frame states that “It will fit a 24 x 2.5 tire with a small clearance”.

I have a CST Cyclops 24 x 2.4 tire on my Nimbus II. I saw a post suggesting it as an alternative to the Hookworm and I was having trouble finding a 24" Hookworm. CST calls it a 2.4 but it has the same ETRTO, 61-507, as the Hookworm. There is 1/4" clearance on either side of the tire and 3/16" clearance to the crown. The 2.3 K-Rad is 58-507, it should have at least this much clearance, if not a little more.

The K-Rad does have a round profile, I had this tire in 2.1 on a Torker LX. I never rode it in dirt or mud though.


Ha-ha! Thank you! I didn’t think of looking for the frame specs on UDC, should have and will tuck that away in the recesses of my mind. Can you explain what that string of five numbers, and the “ETRTO” bit means? It’s something to do with measurements, is the first bit tire width, and the second bit tire height?

The first two numbers are the with in millimetres, the second set of numbers are the bead seat diameter, or rim size.

Thanks much!