Gaining Traction: 27.5+

Have you heard of 27.5+? Heard about it but still a little confused? You’re not alone! Here at Cyclepath, we’ve been fielding tons of questions about mountain biking’s newest “standard” and we’re here to help address the confusion.

Devinci Hendrix Maxxis Chronicle 3in Tire

Simply put, 27.5+ takes the popular 27.5″ wheel platform and makes it wider. Tire size goes from your average 2.3″ up to an average 3.0″ and rim width expands accordingly to provide tire support. All this mass means wider hub spacing is needed too – which means, you guessed it – you need a new frame and fork to run an optimized 27.5+ setup.

The increase in hub width – called Boost spacing – means 100mm front hubs jump to 110mm and the rear 142mm gets bumped out to 148mm. Boost accomplishes two things: first, it creates more space within the frame and fork to handle the increased volume of 3″ wide tires.

The second feature is less obvious; the increased distance between hub flanges translates to an increase in wheel stiffness, thanks to a wider spoke bracing angle. This becomes significant when you consider that the 27.5+ tire is not just wider – it’s taller as well. The outer diameter is roughly equivalent to a 29er wheel with a 2.25″ tire, making the two interchangeable. In other words, the new 27.5+ platform means you’ve essentially got two bikes in one – a 27.5+ bike for maximum grip, comfort and stability, and a 29er trail bike with lighter wheels that are purportedly as laterally stiff as 27.5″.

Devinci Hendrix Swingarm Tire Clearance

Get a Grip: Why Go 27.5+

In 2015, we saw two major trends in mountain biking tech: a push to maximize rim widths and a resurgence in popularity of the 29er, thanks to refined geometries featuring slacker head tubes and short chainstays. The best 27.5+bikes can be viewed as a natural evolution and synthesis of these two trends. Take the speed, rollover capability and geometry of the new gen. 29er and mate it to a 3″ tire for absurd traction, control and comfort, and you’ve got 27.5+.

That’s the rational argument. But for all the talk of increased contact patches and super-low tire pressures, we think there’s a more compelling argument – 27.5+ bikes are fun as hell! Semi-fat tires provide incredible grip and stability in the gnarliest conditions and they want to roll over everything you throw at them, without the sluggish feel of true fat bike tires. Simply put, 27.5+ means more fun on more trails in more diverse conditions for more of the year. This is particularly attractive for those of us who live in climates that provide plenty of “less than ideal conditions.”

Is 27.5+ for you?

The answer is…a definite maybe. Like everything in our industry, whether or not a product is right for you depends on your specific wants and needs. One thing is certain – the positives of 27.5+ make for a pretty compelling argument, and now that nearly every major frame and component manufacturer have gotten onboard, we can confidently say that the mid-fat standard will be here for the foreseeable future.

27.5+ Conversions

In some cases, you may be able to convert your existing 29er to run 27.5+ wheels and tires, with a few caveats. If you’re working with a frame we’re familiar with, we may be able to help from a distance, but generally these conversions are case by case and require some trial and error setup in the shop. For more information, please contact us here: info@cyclepathpdx.com.

  • Disclaimer: this article is meant as a general introduction to 27.5+ and is not intended to be exhaustive or the final say on the matter. Please contact us with questions here: info@cycleapthpdx.com.
Posted by on January 13th 2016