The flavor of the week in mountain bikes is 27.5+, with a handful of companies debuting bikes built around the new size at Sea Otter last week. And rumors of more such bikes .
The sell on this new size is the ability to run decreased tire pressures, which results in聽increased traction and control. Of course,聽we already had a standard that offered all of that鈥攊t鈥檚 called 29+. We鈥檝e loved every 29+ we鈥檝e ridden, so why the abrupt switch toward 27.5+?
Over the last year, as I began hearing about the new size and grilling manufacturers over why they don鈥檛 just stick with the 29+ format, most have alluded to the difficulties that the extra dimensions and weight pose. Rocky Mountain put it like this: 鈥淲e needed a low-pressure, high-volume tire that didn鈥檛 exceed traditional 29er outer diameters鈥he [27.5+] outer diameter allowed us to design the Sherpa with proper full suspension in a full range of sizes.鈥
To paraphrase: it鈥檚 tricky to fit in all the bike鈥檚 bits and pieces and keep the ride quick and fun and light when the wheels get too big. And that鈥檚 especially tough with full聽suspension. (Though we know of at least one company, ,聽that鈥檚 done it.)
So, just three years after they launched, are 29+ bikes dead? Given the sudden momentum for 27.5+, we鈥檇 be tempted to say yes. Except that amid all the hype over the new standard, Trek last week announced its , which is built around 29+ wheels. Not to put to fine a point on it, but the largest bike company in the United States is investing in 29+.
鈥淲e tried all the sizes in developing the new Stache, and the 29+ was definitely the best option,鈥 says Travis Ott, mountain bike brand manager for Trek. 鈥淚t was easy to get to 27.5+ from an engineering standpoint because it鈥檚 the same size as a standard 29er so all you have to do is add a bit more clearance. But when we tested 27.5+, we thought, 鈥榃ell, it just feels like a 29er again.鈥 It took a lot of work and some pretty extreme measures to get the Stache right at 29+. But it feels like something new and better. The traction, stability, and confidence are unequaled.鈥
We loved the original Stache, a 29-inch, all-mountain, aluminum hard tail with a slack front end and a 120mm fork. So we鈥檒l be sold if the 29+ is better than that.
The Stache will be available in an alloy frame only and run three-inch 29+ Bontrager Chupucabra tires on 50mm-wide rims. 鈥淥ne of the big criticisms of 29+ is the excess rotational weight, but that Chupucabra is sub-900 grams, which is lighter than many of the 27.5+ tires out there,鈥 Ott says. The bike will use new wider axles on both wheels: Boost 148 in the rear and Boost110 in the front, both of which add stiffness for the oversize hoops and help with the chain-line issues presented by fatter tires.
Trek has also developed an interesting elevated chain stay design on the drive side, which allows the company to keep the rear end of the bike tight鈥攖hus getting around some of the issues that others say 29+ poses. Because of the design, however, the bike will only work with single-ring setups up front.
Perhaps the most interesting thing about the new Stache is the rear Stranglehold dropout, which allows the axle path to be adjusted fore and aft by 15mm. This means that the Stache isn鈥檛 restricted to 29+. Trek is even releasing measures and fork details for optimizing the bike with 29+, 27.5+, and 29-inch wheels.
That鈥檚 an interesting point because it shows that Trek isn鈥檛 dead set on the 29+. 鈥淔or the trail hardtail, it is the best option,鈥 Ott reiterates. The implication, of course, is that it may not be the perfect size for a full-suspension bike, though Ott wouldn鈥檛 be drawn into that speculation. 鈥淚 don鈥檛 want to back us into a corner. We are looking at all sizes, including 29+ and 27.5+. It鈥檚 always a question of choosing the best technologies for the platform.鈥
The Stache will come in three models, two of which (9 and 5) are available for purchase now. The Stache 9 ($3,880) and 7 ($2,520) will run 110mm Manitou suspension forks, while the Stache 5 ($1,760) will get a rigid carbon fork. There is also a frame-only option ($940) for those who want to build their own.