My excellent talk with John D. (UDC)

I had the opportunity to speak on the phone with John Drummond, owner of UDC, (USA) today. He was friendly and very forthcoming with regard to the “X” airfoil issue, and told me that the problem has been discovered to be mostly likely caused by a defective batch of bad tubes! They have since replaced these with coker tubes, which seems to have solved any suspected Airfoil/TA tire conflict. :smiley:

Let me also make clear that if I “implied” that UDC had been “less than truthful” in a previous thread, I will retract that here and now. It can get very frustrating when you get conflicting information from one source to the next, so it gets pretty hard to know who to believe, but I do not now, nor did I then believe UDC to be untruthful in any way. At worst I think they may simply have not known about the problem to its full extent, or in all its details. They certainly do NOW, so that’s a good thing, as both John and I agree! :slight_smile:

In the past, UDC has always been quick to respond to questions or complaints, and replaced my broken KH Muni rim (remember that bad batch with the “seam” in the rim?) and a broken magura part, a split lift handle…all were replaced free of charge and shipping, quickly and without question. So my experiences with UDC have always been excellent.

As I told John, I like to do my research before I buy an expensive unicycle or whatever, so when I initially came upon various threads saying that the new “x” rims were faulty, it gave me pause. That’s why I called them to inquire, and so when they said they hadn’t heard of the problem, I just became uncertain as to how to make an informed decision, with so many conflicting reports about this rim, and no explanation (until today) of why the problem might or might not exist.

Just so you all know, I am now quite confident in making my purchase from UDC USA, and plan to buy a 36-er with the current airfoil. John also wants to make clear (as he will in his own post) that they will stand behind this rim, and if I experience any problem with it, to contact him directly so that he can take care of the problem.

Our conversation was ended on a friendly, positive note, and I look forward to getting my new 36-er, and I now feel comfortable saying to anyone contemplating whether or not to buy one to go ahead and order one with confidence.

In the end, all I wanted was assurance, (from UDC) and some kind of explanation as to why some people were having problems with this rim, as people were thinking it was either the fault of the rim, or the tire. When John told me about a bad batch of TUBES being the likely culprit, and that they have recently gone back to using ONLY the coker tube, the problem seems to have been solved.

I will post a thread reporting the performance of my new 36-er w/”x” rim after about 2 weeks worth of initial riding. I’m hoping for the best!

Wait, am I mistaken? I thought the problem was that the Airfoil didn’t work well with the Coker tire. Did you mean to say Coker, or is that part of the problem still unresolved here?

I note your use of the phrase “most likely”. Seems like evidence points to a problem with the tubes but that no one can conclusively prove it or explain the mechanical processes that occur there. I’ll be waiting quietly while more experience/data is collected by all the folks running the Airfoil rims.

Thanks, Terry, for going all out to get some clarification on this issue!

The coker tire is not, and was never an issue for me because I read the UDC disclaimer, as most everyone has, stating that the Coker TIRE was not compatible with the “X” rim. But the coker tube is now being used with the TA & X rim with no known issues, whereas the previously supplied tubes that were recently shipped with this Tire/rim combo have been found to be defective. But you’re right; Time will tell. I just feel more confident in buying this rim with the coker tube now that I have first hand assurance directly from John Drummond.

I’m curious: what was actually the problem with the tubes that would cause these problems to occur? I was under the impression people had had problems with blowouts… what kind of tube fault can cause that?

If the tubes in question were 29" ones, I can see where they might put more pressure on the bead area of the tire, and less on the outer part. This would create more pressure between the bead and rim, without the fatter part of the tire to the outside to help hold things together. Just a guess.

John Drummond also mentioned to me that the X batch of Airfoil rims was exactly the size they were supposed to be, after being completely redone at the factory. The original X batch were too big, actually larger than the original Airfoils! The second batch were made a little smaller because of complaints from people changing tires. They are currently on the third batch of Airfoil rims, and everything seems to be okay though you must watch your tire pressure. You don’t need to run lots of pressure in a 36" anyway.

Now with the new Cokers coming out, hopefully the tire and rim compatibility thing will settle down to a fixed and consistent size, so all us weirdos can mix & match them!

John said it was a stem defect that was causing blowouts. Wait to read John’s own post on this subject.

Nope, 36" tubes.

I just thought I would post my experience with the X-Airfoil here as it seems to support this conclusion.

When I first ordered my Nimbus 36" in February, it arrived and I took it out of the box and assembled it. I did not have time to cut down the seat post and give it a test run before I had to go to work. I never checked or changed the air pressure in the tire, it was at whatever pressure it had been shipped with from UDC. When I got back from work (only 2 hours later) to my surprise the tire had blown off the rim and there was a hole about 2 inches long in the tube in this location. I contacted UDC about the problem, and was promptly sent a new tube. I was told that there had been a problem with a defective batch of tubes.

After installing and inflating the new tube, being especially careful to seat the bead correctly, I was still a little suspicious of the tire/rim situation. However, I have had no problems with it since then, and my suspicion has slowly died with time. I generally ride with 40-45psi and have been on several 20-30 mile rides on it. I have not done any muni on it, although I have gone down curbs and such a couple times with no problems.

Now that school is out for me I should be able to take my 36er out for a lot more rides. I will post here if I experience any X-Airfoil related problems.


Wow! That does indeed seem to support UDC’s statement regarding bad tubes! Thanks for your post and keep us “posted”!:smiley:

It is strange, and something I wouldn’t suspect, that a problem with a 36" tube could cause the tire to blow off the rim. I’m not sure what the suspected tube defect could be. My best guess is that the valve stem might be a possibility. Maybe the rubber was extra thick there or extra large and pushed the edges of the tire the wrong way. The valve stem area can be a problematic area making it difficult to get a tire correctly seated on some rims with some tubes.

Or maybe some of the tubes had inconsistent rubber thickness and thin areas that herniated and blew off the tire.

I don’t know???

If it is indeed the fault of some faulty tubes at least we know now. Fixing the problem is just a matter of replacing the bad tube with a good tube.

From reading peoples blow-outs, it seems like this is the case.

Ive had the valve problem you mentioned before, but a little different. Long story short, the stem blew of the tube, and about 15 feet into the air, while green slime sprayed from the tire.

Sorry, but I don’t buy the “it’s the tube” alibi. What we need is an objective analysis. I’m no Harper, but last I heard numbers still meant something:

Measure the outside diameter of your 36" rim (airfoil or steel or Quax or whatever). Is it more or less than 805mm (31.7")?

Maybe we could set the standard for 36" rim diameters, such that all manufacturers could know it and use it. Granted, the effective rim diameter (ERD) which is used to determine spoke lengths, may vary from rim design to rim design, but the bead area should be constant.

Take 700c rims for example. While the different designs might have different ERDs, the overall diameter of 700c rims is fairly constant at 630mm, with bead seats (valleys) at 622mm. The parameter standards for bigger rims should be no different in terms of how a rim is measured.

Also another observation: if you look at an airfoil, sometimes you will see that the distance between the 2 spoke holes closest to the weld (directly opposite the valve hole) is LESS than all the other spoke hole distances. Those rims were NOT made like that. It indicates that the rim was cut at the weld, shortened, and re-welded. Take a look at your own rim & see if this is the case.


Objective is good. Insisting that someone is holding back on information is destructive. Let’s keep those rider reports coming and try to make our judgments on the facts, not what feels right.

This fits with what John D. said about the 2nd batch of Airfoils, where they were larger than the first and were returned to the manufacturer to be cut and re-welded.

You aren’t going to wait for Coker’s announcement?

Yes, as we all are. But I also want to have a coker to ride and enjoy asap! Coker only states that the new 36-er will be coming out “soon”. They couldn’t–or wouldn’t–specify when, or even what month.

When mine blew off I noticed later there was damage around the valve, the circular rubber base of the valve had pulled away from the main tube rubber. At the time I presumed that the forces of the tube trying to excape out the gap between the tyre and the rim and led the valve to be ripped off, as obviously it was fixed in place by the stem passing through the rim. Now I’m beginning to wonder about cause and effect. UDC UK doesn’t say which tubes theyre selling, just that they’re appropriate for coker Qu-Ax and UDC 36ers.

Regardless of the “problem” with these rims or tubes or whatever, as Pete said there should be a standard bead seat diameter established. Seems like that wouldn’t be unreasonable to require of a manufacturer. On the other hand it looks like options are on the horizon or here depending on which horizon you live on (QuAx and maybe the new Coker). I’m thankful to have one of the “old reliable” Airfoils myself. I think that QuAx Isis hubs with some of the new multi-drilled KH cranks sounds ideal. Has anyone verified that the KH cranks will fit the QuAx hub? I’d also like to here how the narrower Quax/48 spoke wheelbuilds work with a brake.

Yes, according to the local Qu-ax supplier. They are a tighter fit compared to the qu-ax cranks, but I guess thats actually a good thing.

There is no braking surface on the new Qu-ax rims, which is what stops me from buying one.

Yes, I did. I bought KH double holed cranks in April and put them on my Qu-ax
cross 24" with red isis hub (the same as the one in the new Qu-ax coker).
They fit. At first I had some trouble, because they fit quite tight. After every ride, however, I had to tighten the bolts holding cranks, and now they are well settled – just how they should, I think. :slight_smile:

I still wonder whether to use them on mu quax coker, because they’re quite heavy in comparison to those lightweight quax cranks.