How-To Convert 26" to 27,5" / 650b MTB wheel size

Want to convert your 26 inch MTB to a 27.6 inch? That's a job you can easily do yourself. Converting your 26” mountainbike to a 27.5” or 650b wheelset isn't as hard as you might think. Kees walks you through the steps.

Why are there so many different wheel sizes out there anyway? The image below illustrates the difference between the various sizes. The angle a 29 inch-wheel needs to overcome in order to get over an obstacle is smaller than the angle required by its 26 inch counterpart.

A 29’er then rolls over obstacles more easily. The larger the obstacle, the larger the advantage of a 29 inch wheel gets. Now though, there’s the 27.5” wheel, which for some is the best of both worlds.

There is a snag though: your bike needs to be able to fit the larger wheels. A lot of bikes are being converted to 27.5” and there’s a lot to be said for doing so, but it doesn't use the full potential to be had from a 27.5” wheel.

The conversion of a standard 26” can come with a range of problems, such as inadequate frame clearance or geometry trouble.

Create enough clearance to convert your 26" to 27,5"

So how do you know whether you’ll have enough clearance, both at the front and back? Ask yourself the following questions.

1. Will the rear wheel fit my MTB frame?

Not all 26 inch frames are compatible with a 27.5” wheel, as it can easily rub on the stays or bottom bracket. There’s a number of lists out there, with all the frames suitable for a conversion to 27.5”. 650b Palace has one of those lists on their blog.

2. Will the front wheel fit my fork?

Fox forks are the only forks compatible with 27.5 inch wheels. Rock Shox and Magura forks aren’t, as the tyre will make contact with the arch of the fork. These two brands have made 650b-specific forks however.

3. What happens to the geometry of my MTB?

As the wheels are 1.5 inch larger than before, your bike will stand 0.75 inch taller. This will make the bike feel slightly less nimble through the corners. This is easily compensated however by the extra grip provided by the tyres.