17th December 2014

27.5 inch-wheel mountain bikes – the new standard

Giant Anthem Advanced 27.5 2 '15For 30-odd years, almost every mountain bike rolled on 26 inch wheels. Like many international standards, the 26-inch mountain bike wheel became the norm by accident.

Mountain Bike Wheels – A Short History Lesson

It’s generally accepted that the mountain biking phenomenon got going in the 1970s when Californian cyclists such as Charlie Kelly, Joe Breeze and Gary Fisher, looking for new thrills, began organising downhill races on Marin County trails on single-speed Schwinn beach cruiser bikes.

These Schwinn klunkers rolled on 26×2 inch ballooner tyres. This size of tyre worked fine on dirt, especially when tyre makers created knobbly versions, so 26 inch became established as the standard for MTB wheels.

Mountain bike designers love to think outside the box however and around 10 years ago, some of them asked the question: ‘Taking a blank sheet approach, which size tyre would we use if we were to design the mountain bike from scratch today?’


The answer many came up with was 29 inch. Many riders loved the bigger tyres for their extra cushioning, larger contact patch, better traction, improved ‘rollover’ and their extra speed potential.

What’s not to like? Well, some riders were less impressed by the 29er’s extra weight, slower steering and their comparatively sluggish acceleration till they got up to speed – especially riders below around 5 foot 9 who did not necessarily get on with a bigger bike.

27.5 inch – the happy medium

This encouraged bike designers to come up with an in-between size. 27.5 inch (AKA 650b) wheel mountain bikes first hit the trails in numbers in late 2013.

The vast majority of experienced riders who tried them agreed that 27.5 wheels did indeed offer an improvement on 26 inch without the drawbacks of 29. Such has been their general acceptance, it has taken less than two years for 27.5 inch wheelers to become the new standard to the extent that they now outnumber 26 and 29ers put together in the 2015 catalogues of the major mountain bike companies.

Giant was one of the first companies to champion 27.5 inch wheels. Here’s why in their own words.

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