Archive for November, 2012

I went tubeless this season by trolling the internets for a tubeless wheelset and quick selling one of my tubular wheelsets — pretty much a direct swap. It’s a nice wheelset — American Classic hubs and Stan’s ZTR 355 rims — and chose Clement PDX Crusade tires because I had used them for training last season and was impressed with their performance. I also understood them to work well in tubeless applications even though they are not rated as tubeless tires. I decided to make the switch because tubular tires are really expensive. I was fine with gluing my own tires and really appreciated the performance of tubular. But my tires were wearing and I needed new rubber.

Three races and a few vigorous weekly world sessions later and I have had no issues with the setup and am pleased with the performance. I am absolutely sold on the technology. However, I’ve been reading about racers that have had lots of trouble with their tubeless installations which aroused my curiosity. The conundrum is that there are many people racing successfully with tubeless but there are still a significant number of people unable to do it without catastrophic burping events (CBEs).

I used the local race email list to troll for user experiences and got quite a few, about half of them bad. That’s not surprising since failures elicit an emotional response and thus people are more likely to report poor experiences than good ones. A sampling:

“Raced clinchers before tubeless, and currently racing tubular. Of the 3 systems, tubeless were by far the least reliable for me in race conditions.   Burped tires seriously affected my results in at least 4 races, so I lost all confidence in them for racing.”

“The ride quality is awesome but I have burped my front wheel one too many times. Last time it happened the front tire completely blew out.”

“I would discourage going to tubeless. Maybe I didn’t find the right tire/rim combination but there have been several of my teammates with similar experiences. When running tubeless in cross, the pressure has to be so high in order not to burp air that it doesn’t really give you any advantage over standard tubes. In addition, it is more annoying to set up than standard tubes.”

These disgruntled voices are a marketing liability for manufacturers of tubeless products because they will inhibit acceptance within the cyclocross community. Tubeless for mountain bike is well established and it’s increasing on the road too. And just as road tubeless has a different set of rules than mountain tubeless, cyclocross has enough differences from either that people need to understand the complexities to have success. Here are some of the rules as I’ve been able to ascertain:Burps are the bane of cyclocross and it’s worthwhile to understand how they happen. The tire deforms in such a way as to allow a (temporary) gap between the rim and tire allowing air to escape. Since CX tires don’t have lots of volume, a single burp can make a tire unrideable. The most common pattern is for the wheel to encounter an obstruction that completely deforms the tire to the rim — bottoming out. Depending on sidewall construction and bead security, the sidewall folding can pucker the bead in such a way as to form a gap. Once pressure drops, the tire will bottom out more and probably burp more. A second and rarer method is for lateral forces to pop the bead. This usually results in a CBE and may be paired with a previous bottom out burp.

  1. Just because you can seal up a tire on a rim doesn’t mean you can race on it. There are a lot of variables that determine a viable tubeless racing setup and they go above and beyond holding air.
  2. The bead has to fit tightly. Tubeless specific tires have special beads that don’t stretch and provide a secure connection to rims with adequate bead retention mechanisms. Let me elaborate:
    1. The rim needs a sufficient hook to retain the bead. Since CX requires low pressure, virtually all clincher rims have an adequate hook. However, it also requires a shoulder to prevent the bead from being pushed down into the rim channel when the sidewall deforms. When tubeless conversions cite building up the channel with tape, what this really accomplishes is creating that shoulder on which the bead will rest. You want a really tight fit for the bead between the hook and shoulder.
    2. If the bead stretches, it will be easier to deform and may have enough play to slip over the hook. Using tires that aren’t tubeless specific is a gamble. Mud2 and PDX Crusades set up well and appear to have a bead that resists stretch — for some period of time. The older a non-tubeless tire is, the more the bead stretches. I recommend using those tires for a single season only. And don’t take them off the rim unless absolutely necessary since removal stretches the bead. Double-and never use a tire that blows off the rim for tubeless again — the bead is stretched too much.Note: Every time I’ve heard of a Clement PDX Crusade tire mounted to a Stan’s ZTR burping, the tire was well used.
  3. Tubeless tires on tubeless rims are your best bet for ease of setup and confidence for reliability.
  4. Wider rims appear to be more secure. Since the rim is wider, the tire profile is not quite as high. Perhaps this reduces the pressure sidewall deformation exerts on the bead. Aside: A wider rim will make your tire wider. If you are worried about UCI width requirements, this might concern you. I compared my PDX on the ZTR 355 (wide rim) side by side with a tubular PDX. Mine was 3-4mm wider.
  5. Rider weight, tire pressure, and riding style make a difference. People should be riding a pressure where they are on the cusp of bottoming out on the rough stuff. If you are light and know how to float, you can run ridiculously low pressure. If the opposite is true, then run some more pressure. Sometimes I get the impression that tire pressure is a “how low can you go” pissing match. Experiment and find a pressure that works for you. If you are rattling around on the rim and/or folding over your tires in the corners, it’s too low. If you don’t bottom out ever, it’s too high.

And that’s about it. CXMag already published a three-part series on tubeless how-to and the third installment is really important to take to heart. After trying out my tubeless solution, I divested my wheel collection of the last of my tubular wheels. I’m all in and have no misgivings. Failures can happen with any tubular, tubed clincher or tubeless setup. If tubeless isn’t working well for you, you are doing it wrong — and it’s likely from lack of information rather than poor technical savvy.

At a recent race, one of my teammates commented that he had to run his tubeless solution at a higher PSI than when he used tubes. He then went on to say that he had burped them repeatedly and had even blown one off the rim. He was using Clement PDX on Mavic Ks. I gave him my two minute spiel on tubeless and how I was confident that he could make it work at reasonable (read low) pressures. He seemed weary of the effort and resigned to tubeless not quite living up the hype. I can only hope that he revisited his setup in light of some of my suggestions and you can be sure I’ll follow up.

Since I’ve gotten email from them, I know there are plenty of racers out there like my teammate. I’m not sure what it’s going to take to change minds as quickly as the technology warrants. Maybe companies that make tubeless products should sponsor some ambassadors who dispense their expertise for free at big events. Or they can just wait a few years while best practices emerge piecemeal and the stigma of CBE fades. Personally, I’d want to sell more product now.