Sharing Unicycle Knowledge

I’m opening this with the subject of Compatibility of UNI parts

OK, I have only entered the uni community, about a month ago.

I have discovered that there are 2 common types of uni hubs. 1.) ISIS (International Spline Interface Standard), and 2.) Square taper. ISIS is the “Good” one and Square Taper is the one on beginners, and is generally not as rugged.

I have discovered that there are 3 common ways to mount the cranks to the hub. 1.) Allen screw, into end of hollow shaft. 2.) Nut on end of threaded shaft. 3.) Cotter Pin, with a flat spot on the crank.

Now, I have to learn the standard seat types, and seat post types. And, about the pedals. Do all pedals come in Right and Left, and screw in with a 9/16" wrench? or is there more to this story?

Post what you know, for this thread. Stuff you have learned. We are winding up with about 10 unis, and training others, in this 'hood.

I did not ask for this job, but it is fun, and the kids love unis! This makes me HAPPY HAPPY HAPPY!
Thanks for sharing what you know. There’s nobody else in this community that knows anything, except comments like:

“Whatsamatter, can’t you find the other tire?..If you’d mow your yard, ya might find it!”. Or, “If you’d hold still, I’ll blow up your tire with dis 30-30!” (Yes, I do find it amusing, and funny, but it STILL does not give me information!)

I’m asking for a bit of help, for those inclined.

Thanks Everybody.

There are 3 basic types of hubs:
-cottered on REALLY old unis and older PoC unis (15-25 yrs). These secure w/ a cotter pin.
-Cotterless hubs/cranks. Cranks go on the square end of the axle & secure w/ a bolt, usually w/ a 15mm socket wrench. These hubs have a wide range of strengths, most are no better than cottered hubs. UDC chromo hubs are nearly as strong as some splined hubs (but still use the really weak to weakish cotterless cranks).
-Splined hubs are the only that should be considered for aggressive riding like flat, street, trials or Muni. Hubs and their matching cranks are significantly stronger than cotterless, some more so than others. Now w/ unis everything has been switched to ISIS. U may have trouble finding replacement parts on one of the older styles (I can’t find 145 cranks for my Qu-Ax 10 spline hub anymore). Most secure w/ a bolt into the axle.

There are currently two relatively common post mounts to seats. “4 bolt” on almost everything and the Miyata style which is also on Torker LX’s. There are adapters to mount to modern bike seat posts. Miyata style posts MUST go on Miyata style seats and the same for the standard mount. Since all better seats use the standard 4 holes, I would avoid getting a new uni w/ the Miyata style (LX).

Pedal THREADS use 9/16, (so don’t buy ½” pedals) they usually tighten w/ a 15/mm wrench.

Standard 4 hole unicycle post

Miyata seat post

All the unicycles I know of (which isn’t that many–I’m new to this too) have 9/16" threaded pedals with left-handed threads on one side. But there are also 1/2" threaded pedals out there, so watch out for that. They’re usually used on bicycles with S-shaped one-piece “Ashtabula” cranks. You might well find yourself replacing pedals before too long so that could come up.

Oh, another thing you might run into: the bearings on hubs with square taper axles have a 40mm outside diameter, but the bearings on splined hubs are 42mm OD. Frames are made for one size or the other.

I know that you can use shims to put a square taper hub in frame designed for a splined hub. There seem to be other options, depending it seems on how pliable the bearing cups are, but I’m getting past my depth here.

20" unicycles use ISO 406 mm size tires, 16" actual rim diameter.
24" unicycles use ISO 507 mm size tires, 20" actual rim diameter.
26" unicycles use ISO 559 mm size tires, 22" actual rim diameter.
27.5" unicycles (aka 650b, not many of these yet) use ISO 584 mm size tires, 23" actual rim diameter.
29" unicycles (aka 700c) use ISO 622 mm size tires, 24.5" actual rim diameter.
36" unicycles use ISO 787 mm size tires, 31" actual rim diameter.

Nimbus seat post diameter 25.4 mm
Kris Holm seat post diameter 27.2
Some freestyle and light duty unis’ have an even smaller seat post diameter.

I was going to tell you about standard and miyata type seat posts but skilewis beat me to it. Pedal wise almost if not all standard unis use 9/16 thread.

A little more about splined hubs:
The first one commercially available on a unicycle was the DM ATU, in 1999. DM, the company, stands for David Mariner, the maker. ATU stands for All-Terrain Unicycle. KH used to ride one, shortly before he switched over to his own brand. My second splined MUni used the Profile Racing spec for its spline, which I think has 40 splines. They have always been creaky, but still work fine.

Bolt pattern:
In the 70s, it was the 4-bolt pattern (like KH) and a lot of crap that was much worse. I still refer to that pattern as the Schwinn pattern, as that’s where it came from. The Schwinn pattern may have won out over the Miyata pattern due to its narrower profile (you can make skinnier seats). The Miyata bolt pattern got narrower over the years, but was still wider than the Schwinn pattern.

9/16" has been the standard for many years. Schwinn used 1/2" pedals up through 1983. I still have a load of various 1/2" pedals lying around, and have to be careful not to assume they will fit my other unicycles. All unicycle pedals (unless they are built with tricycle parts) have left and right-hand threads. The same rule applies as it does for bikes; precession.

And watch out for Crank Bros. (and probably other) pedals, that require a 6mm hex wrench to tighten. It’s not an uncommon size, but it’s harder to get decent leverage with the average hex wrench! The very cool-looking (and pricey!) Crank Bros. pedals on my Road machine have no flats on the sides for a regular pedal wrench. :frowning:

Two good tricks I learned are:

  1. When removing pedals, loosen the pedal a few threads (remembering that the left pedal is a left hand thread) with a long pedal spanner to allow the pedal to unscrew easily. Keeping the spanner on the pedal, you can then lift the uni up and ‘pedal’ it in a foreward direction using the spanner to remove the pedal quickly and without getting greasy fingers. It takes a bit of practice to keep the wheel spinning but it saves a lot of time in the long run.

  2. When routing disc brake cables/hoses, route them ‘around’ seatpost. I.E so the hose crosses behind the crown to the other side of the frame (around the right site of the seat tube on an inboard, on the left for an outboard). This allows the cable/hose to be routed closer to the frame (where it is neater and less snaggy) without preventing the seatpost from being removed. To remove your seatpost, all you need to do it loosen your clanp and turn your seat around (so it faces backwards) to make some slack and slide it out.

This is also great for teenagers who insist on growing at a superhuman rate as the ‘twist’ in the hose can be removed at any time which allows the seatpost to be raised much higher.

Koxx-one steel trials 27.2 mm
Nimbus Oracle 25.4 mm

Note: the labeled size for a clamp may be different than the post size. Eg my steel Muni w/ 25.4 post I have a Salsa 28.6mm clamp.

It’s a bit faster if u loosen both pedals slightly then grip the pedals where the wrench goes of both pedals and pedal backwards. One will come off and the other usually significantly loosened. Do the reverse w/ puting the pedals on. Some pedals’ threads don’t turn freely enough to use either Jacobs or my technique.

What about hub bearing spacings? I’d been thinking that 100mm was more or less a normal dimension excepting hubs where a disc brake went inside the fork legs. But I just checked it on mine and was surprised.

My 26" Nimbus muni is 100mm as I expected. My 20" Avenir DLX looked nearly the same but I measured it a few more times and actually it was just a little bigger: right dead on 4", or 101.6mm. My 24" Sun Classic is 92mm, or 3 5/8" if you prefer. (Converts to 92.075mm; the difference is literally the width of a human hair.)

I see that Torker CX and LX and Nimbus E-Sport basketball and track models are also listed as having 92mm bearing spacing.

26" and 29" Nimbus Oregon munis are listed with 128mm spacing. For 36" Nimbus Oregons and UDC Titans, 127mm is given.

For all the Kris Holm models I looked at on UDC, it’s listed at 100mm.

I’d think that fork legs would have enough spring to allow for a difference of a millimeter or two between wheels/hubs. 92mm versus 100mm is a pretty big difference otoh.

the new nimbus alu freestyle unicycles have a 90mm bearing spacing. Im not sure many of the 1mm size differences really matter but whatever you do, dont mix 90-100mm hubs and frames.

Nimbus oracles (except O36), non alu freestyles, munis, trainers etc have 100mm spacings. All KH/QuAx/Triton frames are 100mm

125/5" is used by nimbus/coker on 36ers and the Oregon as it provides more stability as apparently, according to the spoke tightening thread, it is quite easy to taco a 36er. On the other hand, the wide spacing currently rules out schlumpf compatibility but somehow i doubt that nimbus would allow its flagship 36er to go to market without eventual GUni support.


QuAx use a 40mm 48 hole rim
Nimbus use a 42mm 36 hole rim
KH use a 47mm drilled 36 hole rim

The main thing to note is that QuAx still use a 48 spoke design meaning that you will have to get the correct replacement. Bike rims use a variety of spoke hole numbers, so if using a bike rim make sure to get one that can be laced onto the hub.

Steel can usually be stretched a bit w/o significantly reducing strength, aluminum can not. I stretched a 24" LX frame over a 24" DX wheel (100mm hub) w/ problems. My steel Nimbus Muni frame is the proper width but is so stiff it would prob not be a good idea to stretch it over a wider hub.

A lot of desirable bike rims are 32 hole. Of course a 32H hub would be best, but would be more compatible w/ a 48H hub than a 36H.

Great Idea! It’s limited to smaller unis (or longer arms), but it’s definitely a great timesaver If you’ve got pedals with good (easy to turn) threads.

Another tip to do with pedals is to buy a grease gun from your LBS. It’ll really make servicing pedals with a grease port easier and is invaluable when accurate grease application is needed (when re-assembling loose bearing pedals for example).

I only saw the Equinox aluminum freestyle unicycles on the US UDC site, which have 100mm bearing spacing. The Eclipse models on the UK site are 90mm as you say. Maybe those haven’t yet made it to our shores here?

My bad. I typed “36” Nimbus Oregons" when I meant “Oracles.” I don’t think there’s a 36" Oregon. I get those names confused.

Regarding pedals: I went to a velodrome last autumn and brought along my road bike pedals to go on the track bike I rented, since they go with the cleats on my shoes. The track mechanic used a 6mm T-handle Allen wrench through the crank from the back to spin them on, then a pedal wrench on the flats for the last pull to get them snug. I told him that I didn’t even know they had 6mm internal hexes on the axles, and he said, yeah, most pedals do. When I got home, I checked my other bikes, spare pedals, take-offs, etc., and sure enough he was right.

And I just saw an older thread where muni tasmania mentioned carrying a 6mm Allen wrench on the road for when he wants to switch between holes on his dual-hole cranks. I think he said he uses Nukeproof pedals. So I guess at least on some common unicycle pedals, you have both options.

I’ve seen an Eclipse on UDC US before, ~9 or 10 months ago. So either they are temporarily out or no longer carrying them for some reason.

Typo. I meant W/O problems