"X Airfoil" rims?

On UDC, when ordering my new Nimbus 36" I saw the following note:

Please note: The Airfoil rim with an engraved X is slightly smaller than the original Coker single-walled rim; it is not compatible with the Coker brand 36-inch tire. Only the Wheel TA 36-inch tire is compatible with this Airfoil rim.

However, when the unicycle arrived today I could not find an X anywhere on the rim, I even looked under the tire. Where would this X be located?

Another question: With these undersized “X airfoil” rims, has anyone had any problems with the TA tires coming off at high PSI? I am just curious as that is something that comes to mind when thinking about the possible effects of having a slightly undersized rim.

Thanks for any information you can give me regarding these two questions.

We were heading out on a 65 mile ride earlier this week and I set my tire to 35PSI. I have the TA and a 36" stock tube on my airfoil rim with the “X”. 8 miles into it it blew off…bad times. I’ve never known anything to be that intolerant that close to its limit. I suppose it is over, but seriously…3PSI??


3 psi over the 32 recommended. I want to upgrade my stock wheel, but it just doesn’t feel right with less than 50 psi.

I ride mine at 50PSI and would be very dissappointed were I not be able to. Mine is not an “X”. There are other threads on this. I think this rim may be a problem.

Yes, the rim is a problem.

<start broken record mini-rant> But the other problem is UDC’s unwillingness to flex a little “buyer muscle” and reject those things for the crap that they are. I don’t think they’d even have that disclaimer had I not raised the issue when ordering my son’s X-mas Nimbus.

If the current supplier–whom they won’t disclose–isn’t up to the task of delivering quality product, then the world’s largest distributor of unicycling equipment should step up and source an alternative. <end broken record mini-rant>

They said in an email that they aren’t even going to look at buying new stock or finding a new supplier until all of the current ones are sold which is upsetting because I really want to get a coker for this summer but I refuse to do so until the rim issue is fixed. I don’t want the steel rim.

“We won’t have any more airfoil 36 rims for a long time. Since the mess-up, we are looking for a new rim-maker. We have no set date on new airfoils, we just know we won’t be looking for any till the ones we have are sold.”

I would disagree. In fact, I think that everyone who has a steel rimmed Coker or who would like a coker should buy an Airfoil rim.

As far as I see it, the sooner people start buying the shitty small Airfoil rim that has a track record of failure, the sooner the stocks will run out. And the sooner the stock is used up, the sooner they will make more rims which should be back up to normal spec. And the sooner the new rims are available, the sooner I can buy a decent rim myslef.

Well, ok, I admit that maybe I’m being a little selfish here. I would appologise but it would only come across as incincere :smiley:


ok guys i still havent found an answer out.

how do i tell if i have the x rim or not?

ha, I was just chuckling to myself about that. If I knew, I’d tell ya. If you have to resort to calling UDC, please let us know the answer.

Measure the diameter and I will measure mine…

the best measurement i could get was exactly 800mm, how about you?

800mm, take or give a mm but not much difference, and I have the old batch…


well it looks like i might have the non-x version then. that’s good to hear.

do we know how much smaller the x rims are, like 1-2mm or like a whopping 5-6mm?

To measure it correctly you’d need to remove all the spokes and hub so I guess it’s not the best way to do it… for now I wouldn’t be too worried, if it’s only 1 or 2mm then I don’t see you have much trouble with it, I think UDC Australia would have the old rims in stock seeing as they probably dont sell many. Why don’t you ask UDC to make sure?

I’m not positive that this is correct, but I measured our steel rim and our X airfoil. The steel rim was 807mm and the airfoil was 803mm. very slight difference, but I suppose it matters. Further into my rim saga, I replaced the tube with a 29" right after the issue and threw the tire back on at 32PSI…the tire popped out but there was no blowout this time about the same distance later…The tire bead is completely intact and not damaged so I’m not sure what gives. The bike shop looked over it and said the bead was in good shape but very slight in general. They said they put tubular tire bead adhesive on it and put it back on with my spare 36" tube. Its been sitting at 20PSI in the dorm room for a day now just because I’ve been too edgy to ride it. I’ll inflate it and give it a go today on some dead back roads where a potential blow out will not be dangerous. I’ll update when I get back.

A fine point: for evaluating the rim’s compatibility, make a visual inspection of where the bead valley is on the inside of the rim wall. It’s not enough to just measure the overall diameter of the rim, it’s really where the rim bead valley is located.

A course point: when you mount any tire, it has to be centered on the rim. It is possible to have one section of the tire bead mounted outside of the rim’s bead valley. A blowout waiting to happen. JC has made this observation many times before in various threads. Important enough to save your ride.

hey thanks for pointing out the different size/shape of the inner parts of the rim that hold the bead. Makes sense that those would also be different and make a difference in the two designs. It seems like my tire is holding properly now and I inflated it back to 32PSI/rode a short 10 mile day yesterday without problems. Hopefully this thursday will bring a 65mile long ride writeup with it and lack stories of destroyed 36" tubes :stuck_out_tongue:

I concur, I have one of the ‘x’ rims and it is obvious without measurement that the tyre does not sit in it as deeply as it should. Also standing the steel and airfoil rims next to each other the steel is approx. 5mm larger in diametre.

I would send it back. It’s defective (more so than the other “X” rims)

I recently purchased a wheel (airfoil+wheelTA) from uni.com, and I’ve been running it at 45 psi with no problems. 32 is just too low for road riding.