@ Nurse Ben
it looks very interesting !
could you measure caliper width ?
do you think it is compatible with KH spirits and external disk ?
One set is already on an Oracle 29 with D Brake and Spirits, the fit is fine using a 4mm crank spacer. The other is on an Oregon with D Brake and hub mounted rotor, also fits fine.
The only caveat on the cable actuated disc brake is cable stretch which makes the brake lever feel more spngy than a hydraulic disc brake. I may look into a braided low stretch cable to see if that makes a difference in feel.
The Spyre stops well, as good as a hydraulic, easier to feather.
@ Eric (Sas): you know you want one 
You’re welcome! Thanks for your interest! With my lack of mechanical skill and cautious nature I don’t make a very good pioneer but maybe some other people will get involved to push the envelope. I’ll keep plugging away at it because it’s a lot of fun.
I must of missed something, whats a TRP?
A mechanical disk break that’s narrow enough for a unicycle
This:
Sort of related: Beau Hoover does a break assisted coast on his Muni at 2:17
and here at 0:58 (way more impressive IMO)
I used to ride in a full face helmet. It is noisy, hot and uncomfortable.
Jacob spera rides with a full face…
Yes, I’m a convert to brakes (at least on a freewheel unicycle). Corbin also has great examples of brake assisted coasting (Beau-coasting).
I’m still looking for the video of this photo of Ricardo’s:
I just wanna make sure… So this caliper should be fine on a new kh frame w/ spirit cranks?
@Nurse Ben:
would you mind posting some pics of your Oracle 29er with mechanical brake ?
I should have remarked on what an astute observation this actually is. It’s possible to skip the “regular” coasting on a freeride unicycle and alternate between pedaling and the easier brake coasting. This definitely extends the length of off road runs.
I confirmed with Josh at UDC that they will make a wheel from the disc version of the drift trike hub and I’m planning to get an Oracle 24" with a disc brake when the parts are available in September.
It will have to wait until my home internet is fixed or I have time to pay a long trip to Starbucks; this weekend??
The Spyre has identical inside and outside dimensions (measured from the centerline), so unlike typical mechanicals which are wider on the outside dimension, the Spyre is designed dimensionally to be more like a hydraulic.
I seem to remember seeing a line drawing depicting dimensions, but I can’t find it on my old email or on the site. Look under disc brake reviews and you can see my comments and specs.
If you email TRP, I think they have a drawing they can send you. Tell them that you heard about the Spyre from the unicyclist that visited their werehouse in early June 
The Spyre will fit anywhere that a typical hydraulic will fit, the only caveat would be the spacing of the cranks when using a external crank mounted rotor, but this is the same issue for a hydraulic caliper. You should be prepared to play with crank spacers and caliper spacers (thin washers) when setting up Spirits.
Last night I took my first ride on the 36er with the Spyre, it worked well, less abrupt braking than the MT2, not grabby, which was a good thing as I was really tired by the end of the ride and a grabby brake would have sent me sprawling 
Do you think it’s compatible with a twist shifter to adjust drag braking on a road 36 ?
Yes, I was just thinking about that the other day, though I wonder if it would overheat and start to stick.
It really is a quality brake, compares favorabley to a high end hydraulic, pads are Shimano compatible, dual action pistons, it will work with any road of BMX style lever, comes complete with a rotor and IS mount.
The guys at the werehouse are very nice, and even though the brake is spec’d for a 140 or 160 rotor, they swapped me for a 185 on one at no charge.
It was so convenient to drop into their werehouse in Ogden on our cross country trip, they came out and looked at all three of my disc brake outfitted unis, I think they were kind of impressed, made it easier for them to take me seriously when I said that the brakes were going on unis
I’m planning to talk with Josh about adding the Spyre as a brake option, but I need to ride it a little more and work out a time to meet with him and let him ride it.
Fingers crossed he’ll be game once he rides it! When I’m able to get another Muni (someday ) I’d definitely opt to get something without a brake, and add the TRP if UDC isn’t offering the option at the time. It’s not the cheapest brake out there but IMO the easy-peasy cable system is worth it.
So as not to distract from this momentus thread, here’s a link to the Sprye brake review/pics: Disc Brake Reviews: Post what you got!
Okay, now then, about this freewheel thing…
Is it realistic to think that a wheel like this could be build and ridden for technical off road?
If I build one, it’ll be a 26 or 29, though I suppose I could use my Nimbus 24 as a donor…but I want a wheel that is useable for the type of riding I do, XC 29er.
But I need more insight before making the investment, so, is it really possible that with practice a “normal” person could ride a freewheel hub on trails, using the brake to manage the “coasting” stuff and to help manage loss of back pedal control
Waalrus posted that he went on a Muni ride with the thing yesterday, so I’m thinking it has to be doable with a certain amount of practice.
I really think that a wheel build with the Nimbus freewheel hub and a Spyre brake, may be in my future. Think of the down hill!
I’d imagine there’d be a definite learning curve. Even if it took a year to get good at using it, think of how long it takes to be somewhat proficient at any type of Muni.
Please excuse the length of this response. Obviously freewheel unicycling has been on my mind lately.
At this time I can’t say. I don’t ride technical off road myself. I ride muni on a 26" Nimbus Muni and a 29" Torker AX and ride XC on a 36" KH. The trails I ride have few technical sections and when things get too technical I usually walk through (after trying and falling off).
Hopping on a freewheel unicycle is definitely different and I’ve avoided it so far. For one thing the power foot position is 6-12, not 3-9 like on a direct drive unicycle. My caliper brake may not be up to the task of holding the wheel in place during a hop as well. Finally, my current hub is weak and I’m afraid just riding on it will cause it to fail within weeks. Hopping practice may hasten its end.
That said, it may be possible to make the 3-9 position viable over time. That, a stronger brake, and a stronger hub may make it feasible to ride technical sections with a lot of practice (my strong suit) and a lot of bravado (my weak area). I’ll probably be leaving this to others to prove.
A freewheel may require a different set of guidelines for what specs are appropriate on what type of riding. For instance, I’m currently running 100mm cranks on a 20" wheel. My skill at downhill (in general but particularly off road) is not high enough to judge whether different size cranks or a different size wheel would make it easier to ride. I can say that the smaller size (vs. 125) make pedaling smoother which is important. I also find that I can climb fairly steep hills with them although I need to get a larger sample size. All of this is to say that it’s possible a direct drive 29" is more comparable to a freewheel 26" with smaller cranks. At this point who can really say?
Yes, I think it’s possible for a person to ride a freewheel unicycle on XC trails without onerous UPDs without too steep a learning curve. Now that I’ve shifted to a brake oriented riding style (vs. coasting style) I get longer runs that don’t require nearly as much effort or as many balance adjustments. More coordination is required, however, but I expect that over time this will become more natural. My current method is to pedal until I’m going faster than I’m comfortable, braking slightly (an easier version of brake assisted coasting since I can keep my feet on the pedals), then repeating the process. Pedaling is the most stable action and I’m finding that over time I can pedal longer.
It’s important to note that what’s working for me might not work for others. Before freewheeling I had no experience with a brake. It’s possible someone with more experience with a brake would take to it faster. For example, I find it difficult to brake and pedal at the same time. A slight overlap is helpful to me but if I do it too long it results in a UPD every time. On the other hand maybe the braking on a freewheel is fundamentally different and people with lots of direct drive brake experience will have to unlearn what they have learned. I’ll reiterate, who can say?
As far as wheel size goes I think it will be easiest to learn on a smaller wheel, especially with regards to the effect it can have on your body and injuries. I’ve found practice with my 20" freewheel unicycle to be among the safest practice sessions I’ve had. Part of this may be due to being very used to the kinds of UPDs that happen from my very extensive amount of coasting practice, but some of it is due to the distance and position my feet are from the ground. My feet can hit the ground hard but the distance is short and so far I don’t think I’ve fallen to the ground yet. I also maintain a controlled speed which I’m sure is a factor. A larger wheel may mean more serious falls.
I’ve already found enough value in having a freewheel unicycle that I’d be content if my skills progressed no further. I was ecstatic to simply find a way to get the feeling of coasting more often and longer. Even if it doesn’t end up supplanting my regular XC rides I’m finding that there are cross training benefits: improving smooth pedaling and learning to eliminate back pressure.
As far as particulars go I’ve decided to get a 24" Oracle with a freewheel (probably with 114mm cranks). Perhaps we can work something out. If you won’t go as low as a 20" (non Oracle) maybe we could order the 24" Oracle and I could pay for it but send it to you. You could try it out for a couple months and it could inform your decision for what size larger wheel you might want. It might also make for an easier learning curve. When you’re done with it you could ship it to me. And if you find you don’t like it at all there’s no big loss. What do you think? I was planning to wait for UDC US to get the hub but to hasten things along we could order soon from UDC UK and you could order the bigger wheel from UDC US in September.
XC is definitely doable but I’m not committing to an answer on single track muni, especially when it’s rocky or bumpy. As I mentioned above my downhill skills are limited. I’m not sure if there might be an upper limit to the speed I can stay balanced at. I did find a tiny BMX course near me and the rolling terrain seems fun but I’m not ready for even small ramps yet. I made it around one very small banked loop after about ten tries.