12" Trials uni project

Hey guys and girls.

After making this video, I chucked the 12 in the corner and its been there ever since. Recently I bought a new wheel for my trials uni, leaving me with a spare hub and spokes. The rim was no good, it was cracked all around the inside.
So, I started by unlacing the old 19" rim. Some of the spoke nipples were rusted to the spokes so I couldn’t rescue them to re-use, I had to cut a lot of the old spokes to get the hub out.

Once I had seperated the Onza hub from the rim I needed the 12" rim. I unlaced the square-taper hub from the 12" rim which was easy seeing as most of the 16 spokes were snapped!

Now I had all the parts I needed to start building the 12" trials wheel

As you can see the spokes are quite a bit longer than they needed to be. I measured the Onza hub and the 12" rim and worked out that the spokes needed to be about 75mm long. I set to work cutting.

After I had cut enough spokes to the right length I tapped a thread onto the end of each one. I didn’t take any photos of that stage, I have no idea why :thinking: Anyway, heres the result. Before and After

Halfway there!

God my hands hurt after tapping 16 of the buggers!

Now I had all the components I needed. Now, obviously the hub has 36 holes and the rim has 16. Thats 8 spokes shared between 18 holes on each flange. I decided to space the spokes on each flange like so: Spoke-hole-spoke-hole-spoke-hole-spoke-hole-hole-spoke-hole-spoke-hole-spoke-hole-spoke-hole-hole
That way the gaps where there are two empty holes are opposite each other and will be symmetrical.
Sadly I didn’t take any photos of actually lacing the thing. I think I was far too engrossed in making sure I was getting it right to remember to take any.

Anyway, heres the final result!

Yes, there are 3 odd spokes. Thats because I ran out of 12 gauge nipples and couldn’t get hold of any.

Heres a shot with the tyre on. All I need to do now is get some new bearings and chuck it back in the frame.

The cranks I am going to use are 140s. The pedals just touch the floor as they go round, but this is a trials uni, so that won’t matter too much. Skinnys will be fine obviously.

Can’t wait to ride it!



AWESOME :stuck_out_tongue:

that’s sick!!!

bring that baby to buc !

But neither of you are coming to BUC, are you? :wink:

Seriously though… looks cool Edd. Are you going to put a long seat post on it, or leave it small for comedy purposes?


omg thats amazing edd!
if your at teescycle this year you need to bring that!

Thanks Rob. I have got a long-ish seatpost on it. It does look so much better when it has the short one on though because it looks in proportion. It a lot easier to ride with the longer one :slight_smile:

The wheel looks awesome, will be cool to see pics of the whole uni.

Nice one.

Has anyone noticed you used a radial spoke pattern? That’s not going to be very strong. Almost all the tension will be on only a few spokes; the ones in the top part of the rim at any given moment. I think you’re going to break spokes pretty quick, and once they start breaking the wheel will be a lot more weakened than a cross-spoked wheel would be. Total wheel failure may follow within minutes if you keep riding.

Not sure how strong a 16-spoke wheel is going to be, even with the optimum lacing pattern, but the smaller size means you can get away with less spokes. That’s maybe why we don’t see more 12" unicycles being used for Trials and the High Jump.

I have a 12" uni, made from an old high-end kids’ bike. I don’t jump on it, but it’s held up fine since 1984. It also has 16 spokes, but I think they’re in a cross-1 pattern. I don’t have any closeup pictures of it that I can find though, but such a pattern is probably pretty easy to figure out…

I went for the radial pattern because lacing a cross in would have been a nightmare! Especially with the 12guage spokes I was using. This just an experiment really, I will see how it holds up and make any adjustments if I see fit.

Good luck with that. But be prepared to buy more spokes. If the 12g are too fat get something that will work. Right now you’ll have 2-3 spokes taking all the tension at any given time…

!!! Bunny cycle 12" in ISIS !!!

I had also troubles with my 12" doing unreasonable gaps with it, I broke my wheel.
I wanted to see the limits and actualy it surprised me with it’s strength.

I have decided to upgrade it with ISIS hub and trial alloy cranks cut at 89mm (freestyle version used on the signature)

here is my blog with pictures of every step of the repair :


You straightened all your bent spokes and re-used them! :astonished: RESPECT! lol. Looks like im gonna be relacing a cross pattern into mine. Ill see how it fairs with the 13guage spokes first though.


I thought that a lace pattern was important in properly distributing the torque applied when pedaling. This is why road bikes frequently have cross-laced rear wheels and radially laced front wheels. You don’t apply pedaling torque to the front hub and the radial pattern makes a stiffer front wheel. If Edd is not honking on the pedals going up or down steep hills maybe it will be OK. I think that the net torque applied when hopping has to be pretty close to zero.

You may be right about that, but I can’t help thinking a cross pattern will also distribute the load for impacts as well. As a Trials wheel, it’s going to get a lot of impacts on the dominant pedal position, so if the load can be spread to more spokes, I’m sure it will extend the wheels’ lifespan, especially with such a small # of spokes.

I think that the impact forces will be distributed to different spokes but will be distributed just as evenly. For a radial pattern the greatest force for a drop will be on the 12 o’clock spoke which will be in full tension. In a cross pattern, the greatest force will be on the spoke that attaches to the nipple at 12 o’clock. More accurately, the greatest force might be said to be on the most vertical spoke attached to the top of the rim. That is the one that will be in full tension. The rest are in tension approximately according to the cosine of the angle at which they leave the rim with respect to 12 o’clock. That reads well, doesn’t it?

On the other hand, some strength may be added to the wheel due to the friction at the spoke cross points. Crossing the spokes weaves a lot of nice triangles into the geometry although their junctions are not exactly fixed.

does anyone else do trials on a 12?

why thank you:)

I’m with Harper on this one; the number of spokes handling the load at any given time is the same whether they’re laced radially or tangentially. The spokes at the rim are fairly close to parallel, even if they’re laced tangentially.

What radial spoking will cause problems with is spoke wind-up; the hub will have a tendency to twist relative to the rim. This could cause additional spoke breakage, and will almost certainly cause spoke tension issues on a wheel with drive torque.

For the most part, you wouldn’t expect wind-up to be a big deal in Trials. But then I remembered all the hopping you do on uneven/tilted surfaces. Every hop with the wheel facing uphill or downhill will introduce wind-up, which will greatly increase metal fatigue in the spokes. Seen it happen with the old original Semcycles, but more in a basketball environment than a Trials one. :slight_smile: