Fat and fast: SRAM’s XX1 drivetrain helps keep things running
strong in adverse conditions. Borealis’ carbon fork not only
looks the part, but is stiff enough to handle the excess force of
the wheels. The stout bottom bracket provides efficient power
transfer while fitting around the wide tires.
Bottom bracket height
Top tube length
Head tube angle
Seat tube angle
28. 6 pounds
Surly Rolling Darryl ( 26”)
Surly Bud (f), Surly Lou ( 4. 8”)
WTB Rocket V
Truvativ Noir T40
Truvativ Noir T40 ( 28. 3”)
Race Face Turbine
Race Face Narrow Wide (32T)
SRAM XX1 11-cog (10-12-14-16-18-21-24-28-32-36-42)
24. 3 feet (per crank rotation)
5. 8 feet (per crank rotation)
None (weighed with Shimano XT)
Beyond snow: Fat bikes are most well-known for their ability
to handle snow, but they also excel anywhere traction is low,
including sandy or shale-covered trails.
BOREALIS YAMPA XX1
will eat up a few hits at a time, but try to send it through a
rough section with repeated hits and it’ll remind you that
at its heart is a rigid frame.
Braking: Avid’s XX brakes paired with 6-inch rotors do
an adequate job of getting the Yampa shut down, but we’d
opt for a bit larger rotor in the front to help the brake
work a little less hard.
TRICKS, UPGRADES OR TIPS?
The 32-tooth chainring is okay for areas with mellow
climbs and packed snow or sand, but if you plan to tackle steeper climbs or thicker trail surfaces, we’d opt for a
30-tooth to help make more of the cassette usable.
Take the time to experiment with tire pressure.
Depending on the terrain, we found anything from about
6–10 psi was ideal.
The Yampa probably won’t be the first choice for the
casual mountain biker who wants to try his hand at fat
biking, but that’s not the point. While there are plenty
more basic fat-bike options out there, Borealis is making
bikes for riders who see fat biking as more than an off-season hobby. ❏