ENVE Composites' Twenty9 XC carbon fiber mountain bike rim has always been marketed as tubeless-compatible but now it's official, having earned genuine UST certification from the standard-keepers over at Mavic.
Moreover, ENVE say that information gleaned from the company's high-profile sponsorship of the Santa Cruz Syndicate downhill team has helped make the latest version of the 29in cross-country rim stronger and more rigid than earlier iterations thanks to use of more impact-resistant laminates. Claimed weight for a single 24mm-wide (external; 18mm internal), 31mm-deep hoop is just 385g, as compared to 330g for the equivalent 26in version.
"Our investment in new testing equipment has strengthened our ability to take real world results and feedback, validate it in the lab and then reintroduce it to the athletes and testers to validate any of the changes we've made," said ENVE engineer Kevin Nelson in a press release. "This process is very apparent with our new cross-country mountain bike rims. We took what we were learning from our test riders and made changes accordingly. As a result, the new rims are stiffer, stronger, and now tubeless."
As with all of the company's rims, one of the Twenty9 XC's defining features is its molded-in spoke holes, which are said to be stronger than ones that are drilled conventionally since no fibers have to be cut. The internal nipples still require pierced outer rim walls for access, though, so tubeless setups will require the use of airtight rim strips.
The ENVE rim's pierced outer wall requires the use of an airtight rim strip in order to be run tubeless
Unfortunately, ENVE still haven't gotten around the tubeless issue on their more versatile AM rims. According to the company's Jason Schiers, the wider rim profile has proven harder to adapt to UST in carbon and development has been pushed back far enough that there's no set timeline for release. Schiers says official UST approval for ENVE's Twenty6 XC rim is pending, however, with the delay being attributed to nuances in the approval process between the two different sizes.
However, one might wonder: Why the emphasis on UST certification when others – notably NoTubes and other companies like Sun-Ringlé who use the same licensed shape – have managed to successfully do the tubeless thing using rim profiles of their own design? "We talked about doing our own and potentially working with Stan [Koziatek – founder and namesake of Stan's NoTubes]," Schiers told BikeRadar. "[But] UST to us seemed the most user friendly and you have an enormous tire selection. It was an easy decision after all things were considered.
"The unique thing about UST is that they really push the concept that it can be inflated with a floor pump and not require a compressor. It was more challenging than we expected to get approval, especially with the holes in the rim, but the bead lock concept is an additional security feature that we thought was attractive both as a manufacturer and for consumers."
ENVE will offer the new Twenty9 XC as part of a complete wheelset with DT Swiss or Chris King hubs, or as standalone rims in 28- or 32-hole. Pricing is expectedly on the premium side of things. A set of Twenty9 XC tubeless clincher rims laced to Chris King quick-release hubs will run you US$2,550; subbing in a pair of DT Swiss 240s hubs will change that to $2,500; and using through-axle DT Swiss hubs will cost $2,520. The bare rims will cost $899 each.
ENVE Composites feel the true UST rim bed profile offers consumers a more secure tire fit and easier inflation than other tubeless designs