Fatbikes have been a growth area but the next big trend may be towards semi-fat tyres—more specifically the 27.5+ size. Based on the middle wheel size, they will run 3.0 to 3.5 inch tyres along with appropriately wide rims.
What’s the point? True fatbikes are designed to excel where flotation
is the overriding goal; soft sand and snow. The 27.5+ bikes are likely to serve
as regular trail bikes whilst still offering enhanced traction and flotation.
Its exact use remains somewhat up in the air but suspension manufacturers Fox
and RockShox have announced that they’ll be making 27.5+ compatible forks, and
to make space for the wider rims and tyres, we are now seeing more new axle standards.
2016 FOX
Fox will be offering a 110 - 150mm travel fork that specifically caters
to the 27.5+ market. It employs a 110mm wide, 15mm diameter thruaxle. This
allows the rotor and hub flanges to be moved outboard by 5mm, providing better
triangulation and a stiffer wheel. It also means that you’ll need a special
110x15 front hub and the different rotor position means you can’t just space
the end caps 5mm further out on a current 100x15 hub. Apparently this new fork
will clear tyres up to 3.25 inches wide.
Aside from being 27.5+ compatible, the fork also offers a glimpse of
the features that we can expect to see on their regular fork line. This fork is
based on the Float 34 platform and it features an updated air spring and a new
version of their Fit damper cartridge.
SRAM
RockShox is also introducing a 110x15mm front axle with 5mm wider
spacing on the rotor and hub flanges—SRAM calls it ‘Boost’ and like the Fox
setup it’ll require a special front hub. While Fox has only announced the
110x15 system for their 27.5+ fork, RockShox will employ their Boost hub to increase
the wheel stiffness on a number of regular 27.5 and 29er forks. The Sid, Reba
and Pike will all be offered in a Boost version (27.5 and 29 inch only).
Additionally, there will also be a Boost equipped Pike that will cater to the
emerging semi-fat 27.5+ market.
To complement the wider front end, SRAM will be producing a new rear
hub and drivetrain system dubbed Boost 148. The axle will be 3mm wider on
either side when compared to the existing 142mm axle standard. As with the
front end, the wider spoke flange spacing is aimed at producing a stiffer
wheel. As everything is pushed a fraction further out from the centre line of
the frame, Boost 148 also requires updated cranks to suit a wider 52mm chain
line.
