I have a post coming soon with some final thoughts on road tubeless tires but I thought I’d pass along this article that the Technical Editor at Velonews, Lennard Zinn, penned about a month ago about the dangers of accidently burping tubeless road tires. You can find the full article here.
It is not a secret that you can burp tubeless tires if the pressure is too low or say, you’ve done a ‘ghetto’ tubeless set-up with rims not designed for tubeless use. In the past I’ve heard these stories associated with mountain bike or fat tire wheels. But this article seems to show that burping road tires is also possible and that the consequences can be devastating. No one wants to crash and when it’s caused by equipment failure you really begin to look at and question your equipment choices.
That said, this story has to be framed against the overall picture: there have been plenty of crashes on sewups and clincher tires. No one I know in Different Spokes is still using sewups or even has any experience with sewups. But I did. I stopped using sewups not because of safety but because they’re really a lot more work to maintain than clinchers. Sewups are glued to a tubular rim. Those of us who did use sewups knew that the glue job had to be carefully done in order not to peel a tire off in a turn because it could be devastating just as in the story above. In the 2003 Tour de France Joseba Beloki had a terrible career-ending crash due to a sewup tire coming off his rear rim. (Video here, at 1:44 minutes). If you glued a sewup, you let it cure for days in order to make sure the solvent in the glue was completely evaporated and the adhesion was good. Yet as the Beloki incident shows even glue jobs at the highest level of the sport can fail.
Clinchers have a similar story. Catastrophic failure of clincher tires due to blow-outs are not unknown. If you hit a rock hard at high speed you can instantly deflate it, and since nothing holds the tire on the rim except air pressure you risk crashing just like the dude above. We had exactly this experience on our tandem while touring in France many years ago. We hit a rock with our front tire at high speed (>40 mph) descending and our front tire went flat very quickly. But because of luck and Roger’s excellent tandem instincts and the fact that the curve we were in was very broad he steered the bike straight to a stop just off the road by applying only the rear brake. The tire (and tube) did not come off the rim. Fortunately we did not run out of road.
So yes, you can burp a tubeless road tire and because the tire’s air volume is small you risk deflating it to the point it comes off the rim. Note that Zinn calls a rim with spoke holes “standard” in contrast to “tubeless-specific” rims, which he takes to mean ‘has no spoke holes’. The general point he makes is a good one: be careful when it comes to marketing lingo. Many rims are called “tubeless compatible” and what that means is vague. A rim may have no spoke holes and still not be “tubeless-specific”. The HED Belgium rim in the above story is a “tubeless compatible” rim whatever that means. That said, I use exactly those rims in my tubeless setup. What Zinn doesn’t explicitly mention is the Universal Standard Tubeless (UST) rim and tire combination. This was invented by Mavic, Hutchinson, and Michelin originally for mountain bike tires but they now have moved that over to the road. This has a very specific rim and tire bead shape to help the two interlock and so mitigate the danger of burping and rim-tire detachment. If the above story gives you pause but you still want to try road tubeless, consider using official UST rims and tires. Just know that you will be limited to a small subset of available wheels, rims, and tires, as the UST has not taken off either for mountain or road bikes.