I’ve been having some very strong thoughts about how different unicycle wheels sizes and crank lengths affect the way different unicycle disciplines are used/enjoyed and so on.

The main things I wish to address here are how the crank lengths affect the ratio of each wheel size, whether it is possible to put a different gear on an almost standard unicycle without having buy an £800 hub and which combination of crank length/wheel size gives you which ratio.

So the first one I will address is the last one I just mentioned. I ride a 19" trials/street unicycle with 127mm cranks and I know that there are a couple of standard cranks sizes such as the aforementioned 127mm, the 137mm and the 150mm (apologies if I’ve missed out any standard cranks lengths here). What I would like to know here is what the ratios are and whether there is a calculation to figure this out. I also know that different wheel sizes use different crank sizes as standard. So, for example, a 24" unicycle with a 150mm crank length would have a much easier ratio than a 36" with the same 150mm cranks. So what is standard on each unicycle and how close are the ratios between each wheel size, taking into considertion the use in which the different wheel sizes are intended.

I think that has also covered my other point about gear ratios at the same time.

So onto my last point: As I mentioned before, I ride a 19" trials/street unicycle, which I have 127mm cranks on. If I wanted to ride just trials then a 137mm or 150mm would definitely help me there and also give me more torque. But if I wanted a harder gear to ride, for example, a halfpipe/skatepark then it makes for very dificult riding and control if I go down to a 104mm crank length. So is there a way of increasing the ratio but still using an almost standard 19" unicycle without putting a stupidly expensive hub on it. I also am not sure what ratio I am currently riding or which ratio it is I want to go to, I just know that I want it to be a bit harder so I can go faster without loosing all of my torque!

I’m not saying that I want to have a full set of gears on my unicycle, all I want is a harder gear on my current unicycle (or an adapted one) to try to keep clutter down and also not to add too much weight.

All I can think of currently is to put a moving axle through a fixed gear road bike hub with a cog on, have a cog on the crank, then have two more cogs that would transfer the drive from one to the other. This way you could choose cog sizes to change the gear ration. Does anybody know whether this could work or if anybody has tried it at all.

Sorry if this has been a bit lengthy or boring, or if you feel like you’ve just lost 10minutes of your life to my pointless thread. That in mind, any help/info will be much appreciated.