Nimbus D-brake -vs- Mountain Uni UCM brake mounts

I recently purchased a Nimbus D’brake brake mount to use on my KH36 with existing MU disk brake system. UDC/Nimbus have never stated that the brake mount would work for an outboard disk, and when asked they seem to dodge the question by stating that they were designed to be used in conjunction with their disk hubs.

The reason I wanted to try the D’brake is: I have to take the calliper off the mount every time I remove the wheel with the UCM. Not a major problem but annoying for someone who changes tires/wheels a lot.

Here is the differences I found between the UCM and D’brake mount

Mountain Uni UCM
:)slightly thinner, no clearance problems, mine would just barely work with a schlumpf.
Tighter fit on bearing, less chance of movement
taller brake mount arm,

  • :)places calliper closer to the frame and makes the brake line go strait up.
  • :(caliper needs to be removed when removing wheel

Nimbus D’brake mount
:(wider, would not work with a schlumpf without additional grinding/machining. less than 1mm clearance to spokes (nimbus hub, standard spacers)
looser fit on bearing, easier to remove
shorter brake arm.

  • :(caliper is further from frame and hydro line angles out, could get snagged.
  • :)caliper does not need to be removed when removing the wheel.

I am actually not sure which one I will end up leaving on the unicycle. I can’t feel any difference braking and they both seem to have about the same amount of flex. Basically the UCM tucks things away a bit nicer but adds a step in removing a wheel.

oh and the bolt holes are about 2mm deeper on the D’brake meaning you need slightly shorter bolts. The 18mm(?) bots that come with it are a bit too long. I replaced them with some 16mm socket head bolts.

They did : “The d’brake has been designed to have the disc running on the inside of the frame keeping it welll out the way and allowing the rider to use their existing cranks”

The description you linked to states nothing about external/crank-mounted disk use.

There is really no reason not to use it that way though. I wonder if they don’t mention the outboard disk not to step on anyones toes. I think these adaptors are going to be an important little part in the next few years with people wanting to upgrade their unicycles to disk brakes considering the upcoming disk crank options. (KH, MU, and maybe even Qu-Ax)

Just helping people pick the best equipment for their needs.

It works, which is cool, but yeah the Nimbus brake mount is made for a product yet to arrive…think Spring!

Cool, thanks for the review Eric! I can’t wait until I can get a disc on my GMuni- but am afraid i’ll have to wait a while until the new KH cranks come out. Luckily I have one of brycers magura frankenbrakes on the way to replace my busted one as a temporary fix.


So, contact directly Roger Davies …

hate to say it but inboard means inside the frame attached to the hub , outboard means outside the frame attached to the cranks

Yeah, inboard, like the Oregon, but for a frame that is not currently designed for a disc brake, which means a 100mm bearing spacing, which means a disc hub that is not “yet” available :smiley:

Think Spring.

So UDC says it allows you to use a disc brake on any muni. But you would also need a disc brake hub, too, right? I couldn’t install a disc brake with this mount on a regular isis hub, can I?

nope, you can use your old hub with a d’brake. Although not specified it works just as well with outboard brakes as inboard. All you need is a pair of spirit cranks, the disc calliper and some washers.

However be careful when choosing the calliper as most mechanical brakes are too wide and would hit the crank. There is a thread of what brakes people have used/are using.

Also do not be afraid to spend $10 on a brake line for a mechanical brake. Look at BMX brake lines rather than mountain bike ones.

You’d have to use either KH spirit or Sinz cranks, then you could use your old hub. In fact, since sinz cranks can be purchased in either ISIS or square taper it doesn’t even have to be ISIS if you can get a brake mount that will work with the larger square taper bearings. (There may be others but those are the main ones)

With some washers or adpaters or at least some grinding or rasping ist will probably work at any unicycle. Just make sure, that it has a planar contact surface to the frames bearing housing so that the brake force is lead into the frame and not into the bearing. With bearing housings that are not machined (sheetmetal) you’ll need an adapter to provide this planar face for force transmission. I just made one for my Muni, look here at the german forum for my project with d’Brake and adapter. But also some modified washers will make fine like shown here.

Just installed a nimbus dbrake on oracle frame with KH spirit cranks and external rotor. I used Tektro Augira SUB caliper and I had to place 2 small washers between the dbrake mount, and the caliper mount. Works great!

Eric aus Chemnitz brings up a good point. The MU UCM has a flat top compared to the D’brake’s staggered surfaces. Where the D’brake is tightened on the side with the arm first then snugged up on the other side the UCM would be installed like a normal bearing holder.

I still use both UCM and D’brake with both styles of outboard disk (KH and MU). I now use a washer under the arm side of the UCM to transfer the force to the frame like the D’brake does and both need to be shimmed out to work with the KH cranks as the Spirit cranks place the disk a bit further from the frame than bike cranks with a MU disk would.

I had brought up the spacing issue with Roger when touring in Uzbekistan and he said that the KH cranks with a 6mm spacer puts the disk about 1.5mm further over than the bike standard. Presumably this was done for clearance reasons at the bearing holders.

I did not know, that the UCM does not provide this staggered shape. So thats plus for the d’Brake. It’ll make no sense to tighten the bearing holder with a defined torque for not deforming and so damaging the bearing and on the other side let the whole brake force go radial right into the bearing just to deform it to egg shape.

I wonder if riders with the UCM therefore do have damaged bearings a bit more often. Did anyone have issues with that?

Before I got the D’brake I used the UCM without a spacer, it was like that for at least half a year and I had no issues. These adaptors really should have a firm surface to push on though.

EDIT: I just clicked on your links, nice job. I especially liked the adaptor, did you make it yourself?

It looks much more elegant than just a flat chunk of steel with a hole in it (what I would have done)

Yes, I designed it myself after measuring the bearing housing and the d’Brake and hat it produced by a friend. The major purpose was to guide the sheetmetal bearing housing of the frame to prevent it from bending when tightening the screw. It fits the sheetmetal bearing housing of the QU-AX, if other unis have the same, then it fits them too. I can provide CAD data or manufacturing drawing if needed.

I have a 24" Impact frame with a 24" KH wheel set. Have yet to put anything together. Desire to have internal disc brake. Any idea’s if d-brake will work? I know the KH disc brakes are mounted externally, why? If d-brake would work, what would be best brake?


If you want a internal disk you would need to get a new hub and completely rebuild your wheel, as well as a disk break adaptor and break. If you decide to go external you just need some new cranks with the brake and adaptor, and as a bonus you get strong light dual hole cranks.

Very nice. What type of shop could produce it? What type of material would be suitable? I would like to have the information to have one made. Could you pm the info?