My early XMas present from a UNI bud

I am picking my beast up from a friend this evening who has taken a 36er project under his wing, and I can’t wait take her out for a spin! Here’s the deal:

Nimbus 36er w/ airfoil rim DoubleWide Square Taper hub
Square Taper Double Hole Crank Arms 120mm-140mm
Modulating Avid Dual piston disc Brake
Air Saddle w/ T7 handle

This is an experiment since the disc is on the outside of the frame, but it appear to have the clearance with both frame and calf/foot to be a nice upgrade from a Magura Rim brake that was never meant for an airfoil rim. I’llbe sure to repost once I get a few hours on it to see how it all works:)

36er w_square taper_disc MOD.jpg

Looks good. Waiting to hear how well it works.

An outboard disk break! now why didn’t I think of that?

I am also curious which crank arms you/your bud used to make those double hole ones.

Looks awesome

oh dear, I know my leg would get all caught up on that O_o

looks really good though : ) awesome!

Because you like your ankles? :thinking:

But seriously, I agree it looks great, and I really hope it works. I think figuring out an effective disk brake system for uni’s would be sweet!

It looks really cool!

How could I possibly hit my ankle on the brake? I could see very loose 3/4 length pants being an issue but I don’t wear anything like that, and If I did I would not be above doing the fashion faux-pas to tuck them into my socks to ride that thing. Anything that could snag on that brake could snag on the cranks.

There are a few effective systems but I think this one would be the simplest to implement as it does not require any modification to the hub, but you may encounter some serious problems if the crank comes loose during a ride (that disk is attached to the crank right?)

36er Disc brake MOD

Yes the disc is attached to the crank. Believe it or not, the cranks are actually from a low end kids bike that happens to have a sqaure taper and dual holes, designed to allow for a pedal relocation as the child grows. The cranks are steel not aluminum, so I’m hopeful that the cranks stay tight. I agree a mechanical failure could make for a rough UPD, but the slightest crank creak or wobble should give me enough time to slow her down, and fix. The modulation is far superior to my old maggie set up, and no jerky stops or over-grabbing. The 140 holes seems to be a nice blend of stopping power and smooth spinning. I like it alot so far, and this is the first of a few mods to perfect and hopefully produce a few for sale.

Good point - I wasn’t thinking 3D enough - of course there’s the whole width of the crank in between the ankle and the brake.

Great to hear it’s working! I haven’t tried Maggies, due to the issues you mentioned, combined with the cost, and the fact that cheap v-brakes seem to work pretty well on my 29er. But I do generally prefer disk brakes over v-brakes.

How does the extra width feel, and do you have a spacer on the opposite side to keep it even for both legs? Any possibility of this working with a splined hub and cranks?

36er Disc Brake Mod

There really isn’t any extra width to speak of, and a spacer wasn’t needed, although we did have one prepared just in case. The trickiest part is the mount that attaches the caliper to the frame, as it needs to be precise and ensure that the disc spins straight and true in the caliper.

I dont believe ISIS is an option as you need a 4 or 5 bolt spider off the crank arm to mount the disc.

36er disc MOD 4.jpg

What a sweet idea! I would love a disc brake on my coker; it is really hard to get the rim 100% flat and true.


Is that a normal problem? I put a brake on my Coker and I’m scared to use it. It’s quite grabby. I just go down the hills using my legs.

Share the love…

Who makes those cranks? Where did you get them?

From a few posts up:

I think it partially depends on the condition of the rim – mine has nicks/dings on it at this point, which effects braking. But, it is also quite difficult to get it 100% true. Part of the problem I have is making sure it is vertically true; if it isn’t the slight taper on the rim moves up and down, causing the brake to grab with a different rate depending on the rotational position.

Is it a normal problem? I’m not sure. I have had the problem on several different rims with several different braking surfaces, but only on my 36’ers. the 24’s I can get much more true, and don’t have the same angled rim that the Nimbus Nightrider rim has.

For most people the biggest problem is getting comfortable with a brake – it takes practice + time.


NOTE: my rim is within 1mm true.

I got the description in the post…which low end kids bike?
Does anyone know of a better (aluminum) source?

Another good thing

Another good thing about this set up is it unaffected by any frame flex that’s seems to be inherent to 36er Nimbus’s’s’s. By eliminating the pads and magura set up entirely, I no longer have any issues with the pads inadvertenly hitting the rim with an uphill acceleration, or an abrupt stop

The Franken-brake

Wow, I like the cool look of the disc set-up there, but there may be a simpler solution to the frame flex problem that many of the 36er frames with brakes seem to have. I posted a bit about a hybrid brake that uses the bomb-proof Magura HS22 lever housing (has a larger piston than the HS33) with the short and adjustable HS33 lever blade to get a brake that drives the brake pads a little further - so you can position the pads further away from the wheel and avoid all the annoying brake pad rubbing during idling and acceleration (and the HS33 lever blade is still is spooner compatible).

See the link to the Frankenbrake post below. I’ve ridden a blue franken-brake on my KH36 on two century rides this year and the brakes never touch the rim unless I pull the lever.

BTW: I can make these up for anyone that wants one (I now have Frankenbrakes in day-glo yellow, polished alumiinum, caterpillar yellow, grey, KH blue, red and some sweet NOS black ones) and I’ve got the parts prices/labor down a bit so they are $85/wheel -shipped - for a complete brake for your 36er: Magura modified HS22 Magura brakes for KH36 and 36” Schlumpf wheels: $90 shipped


Hi, you might try adjusting the wheel cylinders/pads so they toe in or out slightly if they grab too much. Adjusting Magura wheel cylinders can be a tediouos trial and error process to get them set up just right for you.

That said, it does take a rather light touch and some practice to get just the right ammt of resistance at speed.

When I first got my 36er I had the grabby inconsistent brake problem. It had a powdercoated airfoil rim and after I sanded all the paint off the sides and polished it up the brake was much more usable. I still think a disk is a great idea though.