This is the new Genesis Bikes 27.5+ prototype, launched at the company’s annual show this week, which takes a steel frame and alloy fork and the new Boost 148 rear axle standard and combines it with 27.5+ wheels and tyres. 

There has been sudden rise in the number of 27.5+ mountain bikes, which take the now popular 27.5in (650b) wheel size and use a wider rim to accommodate up to a 3in tyre. Think of it as a happy medium between a regular mountain bike and a fat bike, well that’s the way some in the industry see them. Whether these bikes are just a fad like the fat bikes which do slowly appear to be retreating into the shadows remains to be seen, but there does seem to be quite a bit of interest in this new standard.

Genesis Bikes have developed this prototype, using a steel frame and 120mm suspension corrected rigid alloy fork – we expect a suspension fork model will be available when the new bike makes it to production.  Details of the geometry haven’t been revealed, but they do let on that it’ll be “long, low and slack,” so it should be a hoot to ride.

The frame has some modern details, particularly at the back-end where we find a Boost 148 rear axle – it’s a 148mm wide axle  which means the hub flanges are more widely spaced and should produce a stiffer wheel than is currently possible with a 142mm rear axle.

Aside from the potentially stiffer wheel, another benefit is improved chainline with shorter chainstays, as the cassette is pushed 3mm further outboard. Meanwhile, up front the alloy fork has a 110mm wide axle with a 15mm bolt-thru axle.

The low slung frame offers generous standover clearance and there’s routing for a dropper post for negotiating steep drops. All the cables are externally routed so it’s easy to service and setup.

The prototype was wearing new Maxxis Chronicle 3×27.5+ tyres, part of the growing choice of wider rubber in this new size.

More at www.genesisbikes.co.uk