Mountainuni Disc Brakes Have Arrived!

MountainUni now has an experimental disk brake setup, and we are seeking a few select individuals whom are willing to give us feedback regarding performance and market viability. Your quality feedback will determine who we’ll select for this test market. This is not an inexpensive venture, but we do feel that this concept will advance the technology of our sport, and feel this forum community could provide key insight!

The process involves having a disk brake mount welded to the frame, and is unique because the rotor attaches to 5 bolt, 110 BCD cranks. Attached is pictures of a protoype (pat. pend.) & its application on a 29er Mountainuni. This type of disk brake system gives consistent and predictable stopping in all environments, and is virtually unaffected by water and mud, unlike the Magura. Our choice of Sins cranks is relevant because of the strength, wide range in sizes from 115-180mm square taper & 135-180mm ISIS lengths at an affordable cost. Yes I said Square Taper too! The development team has a prototype built on my square taper Nimbus 36er and it’s an amazing improvement in braking! We’re also exploring options for dual hole cranks for production peices as well. Again, feedback will help determine what option will be made available for production pieces.

The disk brake mount itself is STEEL and work with fork type steel frames. Aluminum Mounts are in process now, but have not completed proof of concept on Nimbus Nightrider, KH, Hunter, or Coker V2 frames. Pending your own person welding skills, or your connections, welding costs may run as much as $50.00 at a reputable shop. Any Shimano or Grimeca dual piston caplier will work, but we’re happy to guide you on what to buy if your going new. We have both 29ers & 36ers current built with this set up and it is by far, the best consistent braking system to date for Uni’s, and eliminates all “frame-flex” issues associated with bigger wheel braking.

Allow several weeks for us to produce and ship this unique system, as we have a limited quantity. If anyone is interested please inquire through PM or this thread and we’re happy to provide further information. We are not set up for e-commerce yet, but that is coming soon. Please save The “how much” feedback for future discussions, as we’re not ready to take orders. I can tell you we will be less expensive than your “only hydraulic option” today. We will also send setup instructions and pictures for the welder.

Thanks for reading and I hope you like what you see!:slight_smile:
Jeff // Mountainuni

Custom Mountainuni_29er_withdisclogo.jpg

Mountainuni Disc Brake vlogo.jpg

Looks real nice! Have you hade any problems with knocking the disc with your foot or ankle?

No ankle hits

None at All. Even though the disc is outside the frame, but it is still a good measurable distance inside the inner dimension of the crank. I guess the possibility exists, but no issues we can see or anticipate at the moment.


I would definitely be interested in this if it’s possible to get it rigged for the nightrider frame. There have been some frame flex issues with the brakes on that frame, which is why I’ve been holding out on them.


I’m on it…

Disc brake for Nimbus Titan

I was just getting ready to braze-on some brake mounts on my new 36er. The hills here north of Atlanta, and in South Carolina where I ride can be very steep. I would be happy to wait to get your set-up and give you my feedback.

I’m training to do a 100 mile ride for charity in April, so as long as I could get the brake running before then it would be perfect. It’s great to see people like you bringing new innovations to the sport. I know others are running disc brakes on their unis (like lobbybopster), but yours will be available for off the shelf purchase. Keep up the great work!

Interesting that this comes up just as I am starting talks with lobbybopster about getting a similar system built.

I was thinking of having an adaptor made that would screw onto the crank arm like a freewheel on a trials bike crank. It would then allow you to use standard 6 bolt rotors.

I really like your idea though.

My fist thought was that people would rather have a standard disk rather than a oddball disk that may or may not work properly with various calipers. You loose a point there


You found a readily available crank in almost all usable sizes for unicycling where you would need a brake and allow the use of other (bike) cranks without modification to be used. +1

Bolt on system vs screw on system. Yours is less likely to move and can not come undone from applying the brakes while going backwards. +1

unmodified cranks in sizes below 160mm +1

I think I would love to try out your system.

Are you planning on making various sized rotors? I would be curious to see if 203mm rotor would feel similar on a 36er as a 160 would feel on a 26.

One suggestion I would make right away though would be to make the rotors compatible with Hayes, Magura, and Avid calipers, as far as I understand it they need a slightly wider braking surface than the Shimano calipers but the braking surface looks very wide so those calipers you mentioned might just be the ones tested and confirmed to work with the disk. Am I right?

Looks really interesting and I have two questions.

How durable is this build? I ask because everything which is outside the spokes is very vulnerable when the uni falls on some rocks.

Is it somehow compatible with Schlumpf hubs or is a compatible version intended?

Looks really nice- I think Disc brakes are the way to go especially for bigger wheels. Do you find it gets hot and is there a risk of burning your ankles on the brake? Also, what exactly are you patenting? The concept of attaching a disc brake to a bicycle crank has been discussed before, and at least one other prototype has been made, but this is the nicest I’ve seen so far.

I would love to test these but my main unis are KH, so they would require another brake mount. I do have a nightrider too, though.
Schlumpf compatibility would be awesome. Will that be possible?

I would think the main problem with that would be that the Schlumpf ISIS axle has no stop for the crank, and apparently because of its design it can’t use a spacer as a crank stop like other ISIS uni hubs, so you’d need to choose a crank that goes on just enough to get the disc close to the frame without hitting it. But as the OP says it works with square taper (which of course has no crank stop either) then presumably he’s thought of a way round that.

Also, with the brake being on the axle rather than the rim, it would be a lot stronger in low gear than in high gear, but that might actually be a good thing. The other thing is the possibility of breaking the gearing if you slammed the brake on, but that’s probably not going to happen much on a unicycle (except for people landing drops on slopes?)

A couple of general things that come to mind though:

  • For use as a drag brake on a big wheel, is there enough metal there to disperse the heat on a long descent? People get problems using discs as drag brakes on touring bikes because they heat up so much that they boil the fluid or melt the plastic hose at the joint to the caliper. This is mostly from tandem experience though, so the much lighter and slower unicycle may well not have that problem.

  • How wide does that setup end up? It’s hard to imagine from the side view, but it seems like it would end up with a big Q.

  • I’d also be afraid of dropping it on a rock and bending the disc like somebody else mentioned, but that’s a problem with discs on bikes as well - although unicycles do tend to get dropped more often than bikes. If I go out for a bike ride and drop the bike on the ground, it’s pretty unusual. If I go out for a muni ride and DON’T drop it, it’s pretty unusual.


Not only that, the centre of the pedals would be offset towards the side of the brake, possibly giving an uneven-feeling ride.
I imagine that it is significantly heavier than any rim brake?
(sorry, I’m being negative - it’s a great idea and a simple solution to the desire for a disc brake)

Not necessarily - a fair few bikes use symmetrical bottom brackets. Obviously if you used a crankset designed for offset bb though (like most are I think) you’d end up with that problem (unless you made an offset uni hub of course!). Are bike ISIS bb’s usually offset or symmetrical? (I’ve never had a bike with ISIS, but all my sq-taper cranksets have been offset)

I’d have guessed that as well, but there might not be much in it compared with an HS33. Rather than two calipers and mounting brackets you’d have one (slightly bigger) caliper and mounting bracket plus the disc itself and the spider on the crank. Probably a bit heavier, but I doubt it would be that noticeable. I think the main reason for using a disc brake would be keeping it out of the crud so you get consistent braking (same reasons as on a bike), rather than weight saving. And no rim wear, but that’s not really so much of an issue on a unicycle with our relatively light braking habits.


EDIT: I think the OP’s comment that it’ll be cheaper than [a Magura HS33] is interesting though. New, maybe, but HS33s are so common they can be picked up on ebay very cheaply (the two I’ve got on my unicycles cost be £4 and £10 respectively after reselling the other half of the brake, Evo mounts and boosters).

for offroading i would imagine that it could be smashed by a rock pretty easily, but it looks like a great idea for distance cycles.

Ulikely. For those of us who knock our ankles into cranks (we’ve all done it, right?), remember the disk is behind that, so probably impossible for actual ankle or leg contact. Except in a crash. That’s where heat could be a factor, bringing you closer to the experience of motorcycling! :slight_smile: Having the disc on the outside of the frame is of course not the optimum way to do it. You have that problem of possible rock strikes and off-centered-ness. But the reality of the situation is that building a system for inside of the fork would involve a lot more custom work, and would be quite a bit more expensive. The idea here is to bolt and weld something onto an existing unicycle rather than having to buy a whole new one. The biggest drawback on your current model is the square taper cranks. As a disc brake is kind of a high-end add-on, it would seem much more likely to appeal to the users of splined hubs these days. Hopefully you have an ISIS version in the works. From the tone of the OP, it sounds like you’re ready to gear up for a major production run once testing is over. Sounds great! Just remember to have a realistic idea of the size of your market. :slight_smile:

John, I think you missed something. The cranks they’re currently using come in both square and ISIS, in a large variety of sizes.

Sounds like they’ve tried it with both.

Looks interesting, but I’m wondering if this braking system is better than the magura hydraulic rim brake, or just another equally good option. For me the HS33 provides an extremely powerful and sure stopping force, and you can modulate the braking very precisely. It also seems that if the wheel became tweaked, the disk would “wobble” just as the wheel would, making it less effective with the high/low spots.

Wouldn’t the same be true for rim brakes? If the wheel is not true… I get rubbing of my pads.

Plus… I’m pretty sure the axle would have to be bent for it to affect the rotor as it is attached to the cranks, not the wheel specifically. Maybe I’m seeing this wrong but for the rotor to wobble, the crank would also have to wobble… right?

Other than some occassional rubbing with a rim brake, it’s hard to see an advantage to a disc, but as a gear whore I feel the call…

One thing, I don’t want to weld anthing onto my Ti frame that won’t be relevant down the road. However, I do have a Nimbus frame kicking around that would be okay for a little weld.

Why not a bolt on bracket? More saleable for sure.

As to abuse, the location of the disc is likely a safer place than all the brake hose and such on a rim brake, as my recent bent steel braided hose can attest.

Heat will be insignificant with a steel disc, maybe with aluminum it might be an issue. Keeping in mind that we’re not doing emergency stops or traveling at bicycling speeds, there should be a lot less heat build up than on a bike. Socks and shoes should be fine protection.

I wondering how much sensitivity you can get from the disc, that’s a lot more braking power than a rim brake :astonished: