Freewheeling unicycles - The future?
People have been building freewheel unicycles for many years now so it’s about time we had a proper thread for all of the useful information.
Please post below anything freewheel related, especially anything that’s missing from these initial posts so I can keep them up to date and relevant.
Terminology - What do we mean by a freewheel unicycle?
A freewheel (or freewheeling) unicycle, as the name suggests, is a unicycle that freewheels. These typically use a hub with a clutch, which only engages when you’re pedalling forwards.
This means that when you stop pedalling, the unicycle wheel continues to rotate.
Unlike a BC (impossible) wheel that freewheels in both directions and has no method of propulsion or seat, “freewheel unicycle” normally refers to a unicycle with a seat and pedals.
Some people have built freewheel unicycles without pedals rather BMX pegs to put your feet on, but they are even more uncommon than ones with pedals.
Why would someone want a freewheeling unicycle?
Like most questions about unicycling, the short answer is “why not?”
The longer answer is that it’s another skill to learn, and with practice provides rather a different experience and allows you to ride in a way that no other unicycles do.
Are they harder to ride than a fixed wheel unicycle?
Where can I buy one?
Right now, complete freewheel unicycles are not available new. Unicycle.com briefly sold one some years ago but as of right now (July 2021), they have to be purchased either second hand, or built up from parts. Your favourite unicycle supplier may also be able to build up a complete unicycle for you if they have the parts in stock.
People have built freewheels from 20" to 36" so go with whatever you think will work for you. Generally 24"-27.5" would be recommended if you’ve not got a specific size in mind already.
Any 100mm bearing spacing frame with disk brake mounts on the left (internal) side. Nimbus Oracle (up to 29"), Qu-Ax RGB, Qu-Ax QX Series, Mad4One Muni/URC Muni, Flansberrium etc.
Nimbus also have a 100mm dual disk 36" frame coming soon (expected to be available late 2021).
KH frames are not compatible as the disk mount is on the wrong side, although you can weld a tab onto the appropriate size - UDC (UK) sells a kit for this use with the Schlumpf BrakeFast.
D’brake mounts can be used, but are not generally recommended due to flex and vibration that is less than ideal on a freewheel. The now included stiffener plate is an improvement but not a perfect fix.
It should go without saying that to build a freewheel unicycle, you need a freewheeling hub.
As nobody is making a unicycle specific freewheel hub yet, we have to look elsewhere and think a little bit outside of the box.
At this moment the best hubs to use are either the Bicymple 1:1 freewheel hub (ISIS), or the JR Drift Trikes P-Hub (square taper).
This is down to the number of clutch engagement points (24 for each), and so far the lack of failures of these hubs.
Alternatively the Nimbus Drift Trike Disk Hub, or Madazz Trikes Freewheeling Pedal Hub. These are identical in design, and although they’re not quite as good as the JR, plenty of riders use them with no issue. Hardcore riders do have a habit of splitting the hub shell in two though, especially when riding with long cranks, so be careful!
All of the aforementioned hubs are square taper aside from the Bicymple one.
Are there any better hubs? These hubs don't seem to have been designed to handle abuse.
Qu-Ax were planning to release a unicycle specific hub in early 2021 but there have been issues in testing, and COVID-19 has caused many production delays across the industry. This hub uses a sprag clutch which provides instant engagement and is therefore an improvement over the 18 or 24 engagement points of other hubs, and the Qu-Ax Q-Axle interface for cranks - a vast improvement over the square taper options. Now this hub is expected to arrive some time in 2022.
Can I just modify my existing unicycle/wheelset?
Yes, and many people have done exactly this. If going from a stock 100mm Nimbus Oracle or KH wheelset, the spoke lengths required are close enough that you can generally do a straight hub swap (to either the aforementioned Nimbus/Madazz, JR, or Bicymple hubs). Other wheels or hubs may require new spokes depending on their original hub dimensions.
Can I build without a brake?
Yes, but the same hubs would be recommended if you can get them. Obviously then you have more frame options if you’re not considering adding a brake in the future. You could even use a frame designed for square taper hubs with 40mm bearings (see next question).
Do I need to do anything else to make this work?
If you’re using a standard frame designed for 42mm bearings (designed for ISIS or Q-Axle hubs) then for all of the square taper hubs you will either need 1mm bearing shims (sold by UDC), or replacement bearings (17x42x12 - often available on eBay).
If you’re using the Bicymple 1:1 ISIS hub, then you must ensure that you use crank spacers. This is even more important than on a fixed wheel because not only will you likely damage your cranks without, the hub itself will come apart if the spacers are not there to hold it all together. Spacer length will depend on your specific crank choice (~2mm less than the distance between the bearing and the inside of a crank pushed on by hand).
What cranks, at what length?
For either the Nimbus/Madazz, JR P-hub, or other drift trike hubs, you will need square taper (cotterless) cranks.
For the Bicymple hub you need standard ISIS cranks (common on most higher end unicycles).
For the future Qu-Ax hub you will need Q-Axle (or Shimano Hollowtech II) cranks.
As a general rule, go for one size shorter on the length than you would go with a fixed wheel. Extra length is only useful for uphill as if you want to slow down, your brake has to do all of the work.
Can I use x/y/z part or do x/y/z not mentioned in this FAQ?
Absolutely give it a try and let us know how it goes! Freewheel unicycling is very much a new part of our sport and we’re all learning all the time. There’s a wealth of information on this forum about weird and wonderful possibilities too - have a search and see if anyone’s had similar ideas.
Does anyone sell an off-the-shelf freewheel unicycle/wheelset that I can buy?
No, but Qu-Ax may do in 2021 and others may follow. Your local bike shop should also have no issue doing the build/modification for you if you’re not keen on DIY.
Your favourite unicycle supplier may also be able to build up a complete unicycle for you if they have the parts in stock.