There is a lot of controversy, speculation, and misinformation around this topic, so I thought I'd share my experiences with it here. This is not a sponsor driven advertisement post, but instead is my genuine opinion that I have actually had to silence for many years due to sponsors association. I have used it in years past when racing as a privateer and during off season/training in other years when not allowed to race it due to sponsor compliance and of course, now with the Stan's Notubes Elite CX Team. Why so much controversy? Haters need something to hate and traditionalist are going to reject change no matter what it is, but also, it was born in a "cobbled together, use what is available" environment that went wrong for a lot of people.
I think this was one of it biggest early selling points. Someone can take whatever tire and whatever rim, throw a Stan's kit in there and blast air in it with a compressor and there you go. Tubeless! However, the problem with that is lack of standards. So you get an inconsistent rim diameter and an inconsistent tire bead diameter that sometimes resulted in catastrophic failure when run at low pressures in a small volume tire. This caused many folks to write it off as a complete failure and they still hold this belief today. The situation is greatly improved today with Stan's dialing in rims designed to be set up tubeless and tire manufacturers tightening up standards. Before I dive into the real talking points of tubeless tech, I'd like to address a couple points that I believe to be misinformation.
Tubeless tire/rim combos are heavier - I see no reason that this would be the case. We are adding a tire bead, but losing three layers of material that would normally be on the bottom side of a tubular tire (base tape, casing, tube). In my experience, it is quite the opposite. Seems like most people are racing on a 1400g tubular wheel like a Zipp 303. A light tubular tire like a Challenge Chicane is 400-450g. Mud tubular tires even more. I am currently racing on a Stan's Valor wheelset that is 1300g and our Kenda tire selection ranges from 310-340g. Our "heavy" mud tire is 340g. Sure, you add 1-2oz of sealant, but don't we run that in our tubulars anyway? I did.
Tubeless tires won't be as supple - My logic would assume otherwise. We have a volume of air enclosed by a fabric that is attached in 2 different ways, but none-the-less, attached. If the volume of air is the same then, in theory, you can make that fabric to be whatever you want it to be, supple or not, and all things should be equal. The fabric enclosing the air volume in a tubeless tire is 1 layer of stuff. A tubular is 2 layers. 1 layer of stuff generally has the potential to be more flexible than 2. Of course there are some clincher tires that have a really thick 1 layer and therefor aren't as supple as 2 thin layers. However, the set up on my bike now uses 1 layer of thin material that, to me, seems to exceed the casing flexibility of any tubular I have ridden.
Ok, moving on to the claims that are real issues, or at least potential issues.....in my opinion.
Burps - This is an area that I think Stan's has made huge gains in the last couple years. Personally, I have never burped a tire. I don't even know what it sounds like. Does it really sound like a burp? The first thing brought up right here is, "yeah, but you are 135lbs". True. Good argument. However, to compensate, I've put my set up at 10lbs and tried cornering it, with leg out, off camber, hard as I can, to try and put it into an extreme situation that would cause a burp. Nothing. The tire folds over, rim on the ground, but the bead of the tire doesn't budge. However, I do see this as something that could happen and believe there is more to be done in the design department that could eliminate any possibility of this. Some of it has to do with, again, lack of standards. This is something Stan is always wrestling with. Tire bead diameters are getting better, but still all over the place. So Stan has to design a rim that will accommodate all of these, therefor sacrificing a bit of burp resistance in the process. If tires were all held to a high standard and exactly the same bead diameter, then the rim could be made to match it exactly for a perfect, tight fit.
Pinch flats - Without a Stan's rim, a tubeless set up is far more susceptible to these than tubular because the sidewall of the rim is basically putting the tire between a knife edge and immovable object. With a Stan's rim, the rim's sidewall has been designed to be so low, that the material of the tire bead actually hits an object before the rim sidewall has a chance to puncture the tire. In my experience this has proven to be the case. I have been on off road MTB trail rides on my CX bike where I have spend a good portion of it hitting the rim on stuff and been fine. These rides far exceed anything one would experience on an actual cyclocross course. Another design feature that Stan's build into their carbon rims that address this is radial compliance. A Valor wheel, built up, will move vertically, 7mm while maintaining exceptional lateral stiffness. This is huge, for a few reasons. First, CX bikes these days are really rigid. This is adding suspension, but that's a whole other topic. It's relevant here because a rim that moves is likely to hit objects with less force, lessening the force available to compress the tire and it's bead and cut the sidewall. I do, however, still see pinch flats as a place where tubeless tech has more room for innovation. There is still the possibility that an object can bypass the tire bead and hit the sidewall, which is still quite sharp. We will see what the future holds, but for now, the technology is more than capable of running low pressures on a typical cyclocross course without any added risk of pinch flatting.
There is still a world of innovation left in this sector and it is this that I have always like the most about it. The potential for what it could become. It is really just a baby in the cyclocross scene and if it gains some backing and support, it really holds the potential to make things much easier and convenient.....especially for the amateur racer.