To go with 650b or not to go with 650b?

The new bike on the singletrack for the 2013 has a wheel size of 27.5″. You’ve definitely heard the hype over it. The wheel size seems to produce Goldilocks machines: not too big, not too small, but just right. In brief, the 26″ is tops in manoeuvrability, acceleration and travel options. The 29″ has a larger contact patch and diameter that allows it to roll over stuff better than the little guy. The new 27.5″ is more manoeuvrable than 29″, can offer more travel than the large diameter wheel and can get over obstacles better than 26″.

The new guy, however, is not really that new. The wheel size, which is also known as 650b, has been around for a quite some time on touring and randonneur bikes. In the early days of mountain biking, when standards and bike designs were in a great state of flux, the 27.5″ appeared on the bikes by Joe Breeze and Tom Ritchey. About five years ago, 27.5″ wheels were once again on bikes by more independent and adventurous builders. But why, in model year 2013, do the in-between hoops, the “tweeners,” have a notable presence? Part of the reason is parts.

P.J. Hunton, engineering manager who oversees the design, development and engineering of Norco’s bikes, says the 27.5″ was on his radar two years ago. “It had always intrigued us at Norco, but there was never any product to support it, namely forks. As soon as we caught wind that both RockShox and Fox were going to make dedicated 650b forks, we knew that there was an opportunity for us to use that wheel size on a production bike.” For 2013, not only Norco, but Scott and Rocky Mountain rolled out 27.5″- based bikes. Kona and Intense have machines in that category too. So far the bigger brands – Giant, Trek, Cannondale and Specialized – don’t have 27.5″ models, but Giant has shown photos of nearly production-ready models.

So what does this trend mean for you? Do you need the new wheel size in your stable of bikes? If so, why?

If you race XC, the big rolling momentum you can have with a 29er may trump the other features of the 27.5″. “Twenty-nine-inch wheels are slightly more appropriate for cross country riders because they are ultimately concerned with efficiency and less concerned with the fine details of handling.” Hunton says. “Rolling efficiency is more important than optimal weight balance on corners.” Thus, Norco’s 27.5″ offerings, the Sight and the Range, fall into the trail and all-mountain categories, respectively, groups that the company feels are most appropriate for the tweener hoops.

The size of the rider may also be a factor in picking the most appropriate wheel size. The 29″ size can feel too big for more some riders. “For a smaller person, when you have a bigger-wheeled bike, you have a higher centre of gravity,” says Doug Lafavor a designer from Kona Bikes. However, that’s not to say you should treat wheel size as you might treat frame size. It’s not a matter of choosing small, medium or large. Really, it comes down to the type of ride you want. If you are a smaller rider, but want that big rolling advantage of the 29″, go with the 29″. But if you want some of those 29″ advantages – the good contact patch for traction and the better ability to roll over obstacles – you can have them in a more agile 27.5″ bike. Big riders might be into those features too. “You can have a person who is big enough to ride a big-wheeled bike, but he’ll notice that when he goes to a 27.5″ bike, it responds quicker. For example, it might be easier to flick the back end around or to get the front end of the bike up with the smaller wheel. So, it’s become a discerning performance decision for the rider.”

Another feature to consider when deciding between 27.5″ and 29″ is travel. With the smaller wheel size, you can get more travel, a bonus for those freeride folks.

With 27.5″ and 29″ each offering has its own set of pros and cons, it’s the 26″ size that seems like it might get squeezed out by the bigger guys. Its advantages – lending itself to long-travel options and quick accelerations – might not be enough to keep it around, especially if riders gravitate to the Swiss Army knife– array of features that the 27.5″ offers. “This may be a bit of a premature statement, but what we’re looking at is the phasing out of 26″,” says Lafavor. “As far as the trending is going with the 27.5″, we still have to look at what the market is calling for out there. If I was a gambling man, I’d say it’s here to stay. I’m not going to say you’ll see 26″ disappear, but it’s probably on the way out. For a longtravel bike, it will still be easier to design an 8″-travel or 200-to-210-mm-travel bike, so the 26″ may still fill that niche. But, it may all eventually start trending to 27.5″.”

For more on the 27.5″ wheel size, see world champion and Olympic silver medallist Nino Schurter’s video discussion.