So you went and switched to a 29-inch-wheeled mountain bike. Traded in your old ride with its dinky 26-inch wheels and tires. You were sold on the idea that larger mountain bike wheels steamroll over rocks, roots, and ruts and make running lower pressure tubeless tires even better. It’s just too bad the bike business is already moving on the next new thing, 27.5-inch wheels, a.k.a. 650b (the metric name).
Yes, the bike industry is seeking the Goldilocks middle – after going from “small” 26 to big 29, it’s settling on the (maybe) just-right 27.5. Just as in the ski world, where full-bore rocker was then later viewed as an overkill, now with bikes the engineers are saying that big wheels have too-large limitations; some even say privately they wish that the 29er revolution hadn’t happened, that 27.5 came first and supplanted 26, because it combines the best of both sizes.
What it means is that at the bike world’s annual spring industry trade-show in Monterey, California, this week you’ll see a raft of new 27.5 product: SRAM is launching a range of wheel sizes and forks in 27.5 options, Fox will have its'40 FLOAT RC2 downhill fork in a 27.5,'and Shimano will introduce new XT and SLX triple chainring cranksets and XT-level wheels. And this doesn’t even count bikemakers – including Scott, Intense, Rocky Mountain, Norco, Jamis, and now Santa Cruz (with the Bronson, above) – embracing the happy middle.
Why is 27.5 is all of the sudden the new industry darling? We asked some of the leaders of the bike industry, Yeti’s Chris Conroy, SRAM’s David Zimberoff, Specialized’s Sam Benedict, Fox’s Mark Jordan, and Shimano’s Eric Doyne, for their opinions and predictions.
29ers are great…for some applications, and some riders
Yeti’s Conroy says that 29ers'force a lot of compromises. “You need to lower the bottom bracket a great deal, and standover [crotch clearance] gets problematic.” It’s less of a big deal if you’re taller, of course, but for bike designers there are still headaches, especially with more suspension travel. The way the rear wheel travels also gets difficult, or you end up with a very long bike.
Long bikes are difficult to make corner; bikemakers call them “truckish” and it often takes a taller rider to generate the leverage to lean them over. Also, Conroy says, 29ers can make feedback muted. “A lot of what riders like in 26 is a certain playfulness.” Conroy and others argue that you can get that playfulness back with 27.5, and of course a smaller wheel equals a shorter wheelbase, and part of what bikemakers call playfulness is just about quicker cornering.
Big wheels add weight
A less expensive 29er with its larger wheels and tires (and that much more rim, spoke, and rubber) is going to have fairly heavy wheels, says Fox’s Jordan. It’s expensive to make a bigger wheel even close to as light as a smaller one, and as you reduce materials you have to think about flex, too. And of course there’s that much more material in the bike frame, too. Yes, 29ers still have leverage advantages, but pedaling a heavier bike uphill is never fun. You can attack these issues with dollars chasing lighter frames, but deciding to adopt a 29er full-suspension for under $3,000 means you’re buying a heavier bike. Go 27.5 and the engineering challenges are greatly reduced: Less expensive full-suspension 27.5-inch bikes are a lot easier to make reasonably light.
The new-new of 26/27.5/29ers'
Specialized’s Sam Benedict thinks only some'26-inch bikes will give way to 27.5 and that some will stick around. “We see [27.5] more in the longer travel all-mountain/enduro category than anywhere else.” But Fox’s Jordan says 26 is strictly going to be for the low end – Fox already says the shift has happened because they see bikemakers beta testing 27.5 in all forms of racing, from XC to DH. “If there is an advantage to be had with using a different wheel size then the pros want to know. I think it’s going to blow up.” Yeti’s Conroy agrees, especially for gravity.
As for why the shift is happening now, Conroy characterizes the bike industry as perpetual tinkerers, but also explains that while 29ers took a long time to penetrate the marketplace, once that happened it opened eyes. Bring along 27.5 and suddenly parts makers and frame builders wanted to experiment; they didn’t resist. “You have to look at what’s worked. A lot people laughed at the Prince oversized tennis racket – then it really worked. It’s the same thing with an oversized driver head in golf or rocker in skis. When it works you have to try it.”
And Fox’s Jordan'believes that while large-framed 29ers pose some awkwardness, particularly for shorter riders, 27.5, with lower standover, makes most riders comfortable from the first pedal stroke.'”You gain the advantages of bigger wheels without having to change your riding style so most people dig it right away.” Jordan predicts that 27.5 may grow to be the most popular wheel size, period. Hardtail 29ers may still sell well, because you get more inherent cushion from the bigger tire contact patch, but he thinks full-suspension 29 will be more of a niche for taller riders.
SRAM’s Zimberoff and Shimano’s Doyne essentially echoed the idea that 27.5 is going to be a big deal. And though neither was willing to make predictions, they didn’t have to: Their companies are rolling out enough 27.5 product to meet demand, which says that the revolution has already happened. Again.