Nimbus 36" Weakness?

I think the new Nimbus Coker frame have a major weakness. We order a new frame, brake, seat post, seat adapter and seat from Unicycle. Put together the parts and was ready for a test ride. After 7 km we heard a noise from one of the unicycle. After taking a look we recognized it. One of the bearings has loosened from the axle and was pulled out. We have newer have problems with that on the old standard Coker frame, after ridden near 4000 km. I think the four frame legs who goes down to the bearings goes in a not to straight line. The unstraight line will push the bearings out. I think it would be better to have a straighter line down to the bearings to get a press right down on the bearings. The frame should be wider at the top. I also have a Hunter frame. The four frame legs on the Hunter frame has a straighter line down to the bearings. The frame is wider at the top. I think it is important to use Lock Tight to fasten the bearings on the new Nimbus 36" frame. I am also wondering how long the bearings will hold when getting so an unstraight pressure on the bearings. Although it is a lovely frame to a very low price. I am also wondering why the brake is on the front legs on the frame and not on the back legs. I think it looks better at the back, but I have not tried the Nimbus to much in steep downhill to get an experience yet.


for the brake, i think the inside of the two legs protects it better but i can see how it could get in the way of your legs when pedaling. do both of the nimbuses have that bearing problem? you should probally call udc and ask them about it, they willl be able to help better than we will.

by two legs i mean the frame legs.

I appreciate the post. It’s feedback like this that helps to perfect the equipment of this evolving sport. It may also be an anomoly. It will be interesting to see if others have this problem.

put spacerd inbetwen the bearings and cranks problem solved

I don’t think the angle of the fork legs affects that problem much, if at all. The outwards pushing of the frame due to the fork leg angle would be insignificant compared to the actual forces when pedaling. I’m not going to do the statics and dynamics to figure out the forces to see what kind of difference there is, but just going from experience the outward forces on the bearing due to pedaling will be much greater than the weight of the rider pushing down and out through the fork legs.

I have a DM Ringmaster Advanced freestyle unicycle. It has a very stiff frame with straight legs going down. A bearing on that unicycle got loose and slid outward towards the crank. It’s not the fork leg angle. It’s the forces of hard pedaling.

Any axle that has pressed on bearings I no use Loctite sleeve retainer to hold the bearing on. It seems some axles may be undersized (or at the low end of the diameter spec) while some bearings may be oversized (or at the high end of the diameter spec). The combination means you can end up with a loose bearing. Even in an ideal situation I’m not sure that a standard removable press fit is strong enough to hold the bearing in place for a strong rider pedaling hard. I use the Loctite now and haven’t had a problem since.

We only have the problem on one of the unicycles. But we have 4000km on the old coker and never have the problem before with the same wheel. I think I better start using Lock tight now. One major thing could be that it’s easy to over tighten the wheel around the bearings with the new frame. I think if we have over tightened it around the bearings, the bearings roll slower. Get warm, and maybe slip off. Someone told me that a warm bearing expands from a cold bearing.

In some cases a cold bearing can expand to a warm bearing depending on what the material is used/made out of. I agree with zfreak220 about calling UDC and asking for help. They will help you since with whatever problem great or small.

Oh and welcome to unijuul. I and others will help you with whatever questions you may have. So don’t be shy, just ask. We’re like one big happy family here. :smiley: :smiley: :slight_smile: :smiley: :smiley:

In some cases a cold bearing can expand to a warm bearing depending on what the material is used/made out of. I agree with zfreak220 about calling UDC and asking for help. They will help you with whatever problem you have great or small. If they can’t help. There’s always someone on this forum who may.

Oh and welcome to unijuul. I and others will help you with whatever questions you may have. So don’t be shy, just ask. We’re like one big happy family here. :smiley: :smiley: :slight_smile: :smiley: :smiley:

Funny that happened, send a mail, he designed it, I’ve ridden the prototype once, and Roger rode the prototype on both the 10km and the marathon (and a marathon workshop) so I’d say he’s ridden more than 100km on this frame, and thats just Unicon, you might have a faulty frame. I don’t quite see the benefits of this frame besides the bearings, this problem doesn’t make it more tempting to buy the frame…

One thing, you said you have a Hunter frame, why did you buy the Nimbus?

The same thing happens with some stock coker frames. I think it’s because the frames are steel, and can be bent to fit various different width hubs. I think if you bend the frame to be about the right width at the hub then it should stop happening so much.

However, there is one other thing that can go wrong. On my muni, one bearing surface seems to have shrunk slightly so that bearings can just slide on it completely. I dunno how it happened, but it seems to be the case, the old bearings just slid off by hand and the new bearings wouldn’t stay on. On that, I just used superglue to stick the bearing back on, which possibly isn’t the most sensible thing, but I didn’t have loctite sleeve retainer, and I needed to ride it.


I also got the new Nimbus 36. I noticed when putting the wheel on that the frame was too wide by about an inch, my wheel is built with an UDC hub (not the wide one). Simple fix is to bend the frame in, otherwise it would pull the bearings away from center of the hub. They must have designed the frame to fit the wide hubs.

Yes send Roger an email for sure. Its way more likely you had the bad luck of having a faulty bearing than a faulty frame. Luckily these are easily and inexpensively to replace.

Muddycycle - as you’ve discovered the Nimbus 36" frame is indeed designed to fit wide UDC Chromoly hubs.

This is an interesting problem. It is not the frame but the hub that is at fault I guess. It is the press fit between the bearing and the hub. This used to be a problem with unicycle hubs but recently it has been sorted but applying the bearings with a higher load press and a higher tollerance fit. Loctite is the easy answer.

As for bearings on the front and not rear leg it is simply that it is the leg that is directly below the rider and the one with the highest load on it. Should there be any flex in the frame then it is the leg that will have least movement.


oops, I meant brake not bearing in that last paragraph.

Thank you very much everyone.

I think the new Nimbus 36" is a great frame. I cycled 4000km on my old Coker frame before I got a LiweWire/ Hunter. The plan was to get a KH 29" for some more off-road. But I like the wheel big and sold my old 24" MUni. After a while I decided to build a new MUni 36" with my old Coker wheel. So now I use the Hunter at tarmac and gravel and the new Nimbus at some hard Coker MUni.

The tips to use Lock Tight between the bearing and hub were a great idea. I am going to use that in the future.

I would not take the bearings off unless they move. With the new bearings/hubs the problem is normally actually getting them off!

For yours where it has already moved I would take the crank off, slip the bearing off, clean the bearing and the shaft on the hub throughly so that there are no signs of grease, apply the locktite to the shaft and slip it back on using the end of the an old seat-post then put the crank back on.

The other thing I would do is check that the frame has not splayed out when the bearing moved. If you check the bearing spacing on the frame it should be a maximum of 125mm from centre of bearing to centre of bearing. If the frame has been splayed out then squeeze it together gently, ideally you should have it sitting at about 122mm so that there is a little inward load on the bearings.

Hope this helps.


When I had brazed on Magura bosses to the front legs of one of my V-frames, I found that when riding, my legs caught on the outsides of the Magura calipers. I then re-mounted the bosses on the rear legs.
As Roger’s frame also has the brake bosses on the front legs, I’m just wondering has anyone else encountered leg interference when riding?