Back to 27.5
Last year 650b wheels rolled to victory in the cross-country World Cup and the world championships, and were second at the Olympics, all under Swiss superstar Nino Schurter. In less than two years they’ve gone from relative obscurity to forging a substantial presence in the upcoming catalogs of a vast array of bike brands. They are unquestionably the next big thing on the dirt.
Humorously, though, they’re a bit smaller than the last Big Thing — about an inch and a half smaller in diameter.
The 650b, or 27.5-inch, or simply 27, depending on who you ask, (we like 27.5) is being touted as the Goldilocks of wheel sizes. While the 26-inch is often a bit too small, 29-inch can sometimes be too large. Perhaps 27.5 will be just right. But this is not their first rodeo. Defined as having a bead seat diameter of 584mm, the origin of 27.5 is a bit hard to pin down. First, just like 700C tires and rims, you won’t find anything on a “650b” tire or rim measuring that number. Traditionally it has been known as 26-inch x 1.5-inch. While rejected by traditionalists, the 27.5-inch designation serves the purpose of clarifying that it lies between 26-inch and 29-inch mountain bike tires in diameter.
Since we’re never likely to use the most accurate 559mm, 584mm, and 622mm designations for the actual bead-seat diameters for these wheel sizes, we might as well adopt a system that’s clear— we’re calling it 27.5. In the 1960s and ’70s, 27.5 was the traditional size in France for loaded touring bikes, general utility bikes, and tandems. Super Champion churned out rims in that size, and Michelin built tough, 27.5 tires with a deep, road-touring tread. Nokian made winter tires called Hakkapeliitta in that size, including studded ones that were used for racing bikes on frozen lakes in Finland in the 1970s.
Gary Fisher imported Hakkapeliittas for a period in the early 1980s, and he, Tom Ritchey, and some other builders made mountain bikes around them — like the one pictured at left. Lack of further availability of the Nokians killed that early effort, and the wide acceptance of mountain bikes with 26-inch wheels killed their traditional uses in France. Kirk Pacenti, an American frame builder and bicycle designer, almost singlehandedly resurrected the 27.5 wheel size by being a determined evangelist for it. He had 27.5 tires and rims made with his brand and ceaselessly urged bike manufacturers to try them.
Over the past 18 months, 27.5 has spread like wildfire through the industry, largely due to the fear — on the part of many bike manufacturers — that they’ll find themselves off the back again by not moving quickly enough to the new size. Many of these manufacturers (and their retailers and distributors) were stuck with inventory of 26ers when they failed to adopt 29ers rapidly enough; they don’t want that to happen again. Instead, bike shops now have to stock bikes, tires, wheels, and forks in all of three sizes. The 29er itself took years to take hold, even with the urging of industry giants like Gary Fisher. The change came squarely from consumers, who slowly began to demand the bigger wheels, while the latest middle size is being pushed by manufacturers and brands keen on staying out ahead.
It’s almost mind-boggling how quickly the bicycling industry has made available all things 27.5 It was many decades before the real adoption of tubular mountain bike tires in the 26-inch size, despite the best efforts of Vittoria and Fisher decades ago. Tubulars of the 29er variety came around within a handful of years after wide adoption of that size.
But, in that case, equipment to roll the rims already existed, as the size is the same as 700C road tubulars; the rims just needed to be wider. 27.5 tubulars, however, appeared almost instantaneously with the appearance of bikes built for that size.
This time, we can all enjoy the second (or is it third?) coming of the 27.5 wheel size, due to the dizzying array of extremely high-quality bikes, tires, and wheels being made. Reformed 26er riders can roll a bit faster, and converts from 29ers can have lighter bikes that handle more nimbly and fit small riders better. Could it be a win-win situation?
The middle wheel size has seen indecisive branding since its resurgence. Companies are falling on either side of the debat e and some, like Ritchey, initially hedged their bets by using both options. This Ritchey is labeled with the model name P-650b, but early versions of the same bike went by P-275. The tires feature two hot patches, one reading 650×52, and the other 27.5×2.1. Ritchey is now using 650b exclusively, while other brands push 27.5. —LENNARD ZINN