On my mod trials bike I run a 32-hole single wall rim, no eyelets and with huge square weight-saving cut-outs, and it takes 2-metre drops very happily. By contrasts, in the world of unicycles 36-hole double-wall rims with eyelets appears to be the norm, and yet it’s very unlikely a unicycle would ever be put through the rigours most trials bikes regularly endure.
Is there a good reason to use 36 spokes? Has anyone ever messed up a uni wheel? The reason I’m asking is because I’d like to build a unicycle as light as possible, and the wheel is the obvious place to start making weight reductions. There are tons of single-wall 32-hole mod trials bike rim options out there, any one of which which would be lighter than any of the the available unicycle rims. What’s the word?
I’m not a Bike Trials expert, but I’m pretty sure the average jump is landed “softer” due to what I’ll call the Lever Effect. Back wheel touches down, but then the force is kind of spread out as the frame levers downward. With unicycles, it’s always the whole cycle coming straight down, and all of the force must be absorbed by tire and leg compression. We don’t have the “lever” thing to help spread out the impact. I might be wrong about that.
Yes, wheels get destroyed a lot. One of the nice things these days, is that axles/hubs generally hold up. Though they can be broken, today’s ISIS and other splined hubs can take a lot more abuse than the unicycles of old. Trials couldn’t really be a thing with yesterday’s hubs.
Beyond that, there are those that argue that 32 spokes should be enough. Going light is always a choice of compromise. How much strength are you willing to give up in favor of a lighter machine? As a beginner, naturally I would recommend keeping it heavy as you learn. But if you have the means, I’m all in favor of people pushing the limits and sharing their results. At the top levels, I’m sure having a lighter uni will make a difference, especially in a tightly contested contest in hot, humid weather conditions where every gram could make a difference.
Thanks, very good points especially the lever effect thing. Essentially the mass of the rider can decelerate over a greater distance (= longer time), which results in lower forces appearing at the hub. However disk brakes on trials bikes also put a great deal of tensile stress through the spokes, so we can only speculate. I guess the only way to find out would be to try it. I’m not even beginner-level yet, so for my needs anything would do. Anyway, I think I’ill wait for a few more replies to trickle through before doing any shopping.
We should not forget the wheel build itself. All the stock unis come with machine build wheels. They use straight spokes, which is the worst choice. A good handbuild wheel, using butted spokes can take more load. The butted spokes will distribute the load to their neighbours as the have more flexibility. My feeling is that uni makers compensate the “simple” build by using unnecessary heavy rims. So my vote is: Go for a good 32 spokes wheel as you have a knowledge from your trials experiance.
Correction, you can only speculate. Others have already done the hard yards.
Ask yourself why riders with over thirty years experience (such as Kris Holm himself) choose to ride the equipment they do. It is because they repeatedly destroyed the lesser equipment that was available until they designed and built what was required to survive the incredible stresses put on a wheel by hard core unicycling.
Moreover, as a pre-newbie who hasn’t even started riding yet, you are worrying far too much about hardware details.
The vast majority of those who try unicycling never learn to ride at all, let alone have anything like the commitment it takes to learn advanced skills requiring premium hardware.
You can get unicycle rims with cut-outs, or at least with drill-outs. Some people don’t like them because they eliminate the option of experimenting with higher tire pressures, and the amount of weight they save is minimal. If you do other styles of unicycle riding besides trials, or if you are obese, you will sometimes want higher tire pressure. Remember, all of your weight is on just one wheel, all the time (unless you become airborne, of course), so bottoming out is a bit more of a possibility than on two wheels. The KH20 rims have drill-outs, and I have been told they can go to about 80 psi before the innertube and rim tape blow out through the holes. 80 psi should be more than enough pressure for most people most of the time, but this issue is worth knowing about.
As OneTrackMind pretty much said, the weight saved by rim drill-outs is not anything that would help you in a noticeable way until you got to near-championship level, and to do that takes persistence, hard work, and, most difficult of all, you would need to find a real (not virtual) community of trials unicyclists to teach and inspire you.
Yes, I’m probably overthinking this. TBH the main reason trials unicycles appeal to me is because I ride bike trials, which in no way means I’ll ever be able to ride uni trials, although it does mean I enjoy doing tricks and therefore I’m more likely to want to do uni trials than someone who rides a road bike/uni.
At the moment I reckon my main use for a unicycle is likely to be short commutes, with occasional basic trickery such as hopping onto and off kerbs and moderate drops. For this sort of use the weight differences I was worrying about are probably immaterial, as you guys said, so I’ve decided to go with whatever everyone’s using i.e. 36 spokes.
However, I’m reconsidering my options regarding wheel size. Specifically debating whether to go for 19" or 24". Based on what I’ve just been reading, a 24" machine would be a better all-rounder, satisfying the “short commute” requirement whilst still being adequate for a hopping onto and off stuff. However, I’ve read somewhere that 19-20" would be easier to learn on, what do you guys think?
Get a cheap 20" to learn on. Then get a 26" (or larger) for commuting. Practice tricks and trials on the cheap 20 until you break it, then get a decent 19" trials. By the time you’ve done all that, you will know the answers to your original questions.
Cheers!
Yes, 19-20" is definitely easier for learning, and not just for beginner stuff, but later on for advanced skills as well. My 20 is my Wheel of Learning. I use it for trials, freestyle and so on, and I have a 29 road uni that I ride less frequently but for longer trips (up to 20 or 30 miles). Skills acquired on my 20 will sometimes transfer smoothly over to my 29, but not always.
I think this is inaccurate. First of all, KH himself hasn’t destroyed equipment in a long time; he’s too good a rider. Second, I don’t think we have done any sort of rigorous testing on the limits of our equipment. For example, the KH Moment cranks were massively overbuilt (and stupidly heavy) for the forces we put on them. The Spirit cranks use probably 30% less of the same material and they are still fine.
32 spoke wheels are likely more than sufficient for our needs, especially given how bad most of our wheel builds are. They haven’t been extensively tested because almost all of our hubs are 36 hole.
Single-wall rims, I’m not so sure about. We do put more sideways force on our rims than bike riders tend to, and that’s what causes tacoing. But even there we’re probably over-specifying.
In my understanding during the earlier days trials bike rims were somewhat consumable, and were not built for long term durability. Especially considering people took angle grinders and pine tar to them to increase their braking power with Magura brakes. Unicycle trials rims on the other hand were expected to last longer.
Since the Magura days there have been some pretty substantial improvements in design and materials, and the switch to disk brakes have increased the lifespan of trials rims. I think the modern dual wall 32h trials rims would do just fine on a unicycle, especially for an experienced rider.
Since you already ride trials bikes, do tricks, and if you think you will stick with unicycling, I would not hesitate to suggest you get a relatively light Trials, 24 or 26" MUni. You may not be able to ride right away, but your learning curve will be significantly shortened by your past experience balancing on one wheel.
A trails uni generally has around 137 mm cranks and a 2.5 inch tyre. By far the easiest to learn on. But they are slow due to the small diameter, the tyres don’t roll well and the cranks way too long for commuting.
24 is still a bit small for commute and there are a lot more tyre options for 26.
New riders often try to decide on a single uni to do everything but the more you ride the more you will find that you need a whole range of different unis. I have about 16 wheels and only three or four of them are non-core.
You just need to get one and learn to ride. Then you will get to know what you really like doing. It will take a longer to learn on some but still doable. People have learnt on 36ers and even on a giraffe.
If you want to get anywhere on your uni 26 is the smallest I would recommend, but 24 is probably a good size to do tricks as well as move a bit.
36 spokes seems to be a holdover more than an intentional decision by the uni industry. Especially as wheels get smaller the benefit of having more spokes goes away quickly. When rims were generally made of softer material they needed much more support from the spokes, and more frequent spokes helped a lot. Modern rims are much stiffer, and can be built with far fewer spokes, but still I would watch the wheel size. For instance A 36" wheel would be better built with 36 spokes, but a 20" wheel would be fine with 28. It’s more about the space between the spoke holes on the rim, than the number of spokes total.
Of course ultimate strength will be had with a great build. Even tension goes a long way towards a rock solid wheel.
My Freestyle uni has 48 spokes.
It looks cool.
It’s a pain to get the pump in there.
It’s heavy.
I don’t think I’ve ever trued it.
Background: It’s a handmade Wyganowski frame, based around a tandem fork, and is made for the rigors of professional use. In other words, strength is prioritized above most everything else. It’s a little on the heavy side, but it’s never failed me. My previous Freestyle uni had its (Miyata) frame crack, at the beginning of Unicon, a few days before I competed in the Individual Freestyle event.
Unicycle wheels are ALL hand built. They can not be machine built due to the hubs.
Double butted spokes do create more flexible wheels and this can be stronger, but it totally depends on what you are wanting for your wheel. Unicycles are NOT bikes, we actually need as rigid wheel as possible without loss of strength to create the best performance as we are using the wheel to create direction no replying on a combination of 2 wheels.
A long time ago we did some tests on forces on cranks with Onza. They were staggered by the difference in stresses that Unicyclists apply to the cranks opposed to Trials bike riders. Very few trials bikes get up to the forces that a typical unicycle trials rider exerts on their cranks.
Roger, with small flanges hubs, I’m using double butted spokes 2.3/2mm Sapim Strong recommended by Marco Vitale, they allow strong wheels on hub (2.3mm) and nipple (2mm) sides, some of them with 32H rims : so, light and strong both
