Surly Conundrum bearing spacing

It looks like the spacing is around 93mm center to center, and most unicycle hubs are at 100mm center to center.

Anybody know if the Nimbus unicycle hubs have a spacer between the bearing and the hub flange? It looks like there may be one that can be swapped out to change the bearing spacing.

The Conundrum is a frame designed to be used with 100mm hub.

The original specs for the frame give a bearing spacing of 102 to 105mm from outside to outside of the bearing holders.
I have been running one for a while on a blue KH hub (ISIS) and it was fine.

If yours is slightly on the narrow side, gently move it outward when you install the wheel and it will be fine. The frame is CrMo so you won’t break it with your bare hands (except if you are the Hulk).

It’s actually at 105 right on the nose. (outside to outside)

I got the bearings removed, and there are indeed spacers between the bearing and the flange. They measure 5mm.

I’m going to need 1.5-2mm spacers.

You can bend the legs out and get the hub in, but it puts lateral forces on the bearings, and prevents them from spinning freely. It’s 7mm worth of bending the frame.

Keep in mind the 100mm spacing is from center to center and that the bearings are 12mm wide. (112 - 105 = 7mm from above)

all of this is within 1mm, eye/ruler inspection and calipers at the bike shop.

Anyway, food for thought if anybody else needs to look it up later. I’m going to order a couple of washers online (inside diameter is 22mm)

For what it’s worth, a 22mm crush washer can be had at your local ducati dealership for about a dollar or two. I’m heading by the dealership tomorrow to see what they have, and if it will work. But from the looks online, it looks like the ticket. This link will break one day, hence the explanation

Edit: I did call, and all they stock is 4mm and 6mm, so that was kinda out.

How did you remove the bearings and are you going to reuse them?

The bike shop was nice enough to use a bearing puller. They are fine, and they said just bring them back when I find the washers and they’ll reinstall them with the new washers… all free of charge : ) They were genuinely interested in the build, too.


Now my unicycle is part Ducati.

4 of those washers costs $1.50, the dealership had them in stock, and they are exactly 1mm thick.

The end result is an astoundingly accurate 105mm to match the frame perfectly. Slips in like a glove, no flex, no bending, just like factory. I highly recommend anybody building up one to consider this option. Super cheap, and super easy fix.

The spacer on the left side (5.5mm) is what I replaced with the 2mm worth of washers on the inside.

Yes, I considered a Ducati sticker, but that was more than the cost of the washers : P

Very cool. Great to see practical and cheap solutions like that.


100mm spacing is correct, don’t overthink it, a little “out of whack” is not going to harm your bearings unless you ride at sixty miles an hour for 10,000 miles.

If you can do that ^ I want to be your agent :wink:

The spacer between the bearing and hub is generally 2mm per side. I have used less or more when I need to adjust a disc hub to the caliper and when I had clearance issues between the frame and a standard hub.

105 on the surly is 93 center to center. That’s quite a bit off. I could fit it in, but it was putting so much lateral force on the bearings that they didn’t rotate freely. The flange width is what determines how much space you need between the bearings and flange. That can vary hub to hub. Anyway all’s well now. I wasn’t so much worried about the bearings as the frame. Yes it’s steel and can take it but there’s no reason to push it. : P

It looks like the spoke clearance will be tight, but it should be okay. I’d like to see similar views once the wheel is built.

It’s quite tight, but it fits! I may add one more mm to each side.

REALLY nice looking build. Congrats!