Frequently Asked Questions:
"I want to ride on really
loose sand and snow, how do they work?"
Despite their ability to take you places no other bike can go, Fat Bikes do
have their limitations. Even with the 3.7" tires and 65, 80, and now 100mm
rims, you will probably find that they can bog down in really loose
conditions like unconsolidated beach and dune sand, powder and loose
granular snow, shale, and pea gravel.
Often you will be able to ride downhill and maybe even on the level in these
types of conditions but climbing won't work at all and steering can get very
sketchy. You can decrease tire pressure to increase the footprint of the
tires and increase flotation and performance but be aware that no tire can
hold up to prolonged riding at very low air pressures and I've seen a lot of
failed sidewalls and delaminated tire beads from doing just that.
Oftentimes, it's possible to find an alternate line or route to hunt out
those little pockets of firmer goodness and be able to ride without slowly
destroying your tires. On beaches, the sand is firmer where it's still
holding some moisture such as near the tide line.
On snowmobile trails, the trail is loosest where the machine's track has
rototilled the snow but it's often good riding if you can stay on the ski
track, the proverbial "thin white line". A wonderful feature of snow is it's
property of sintering, or packing down and becoming firmer after it's been
disturbed so if you wait a little while after traffic, it usually gets
firmer and much more ridable. Likewise, drifted snow can firm up into white
slick rock dunes which make for incredible riding. If you're riding in a
group, switching trail breaking duties will spread the burden out among your
companions.
An ironic thing, when I first started building FatBikes, I kind of intended
them as a great equalizer for bigger, heavier riders because light people
floated sooo much better on the SnowCat rims which were the current state of
the art. And it worked great for a while but then smaller people started
getting their hands on FatBikes and now guess what, we're right back to
square one. In retrospect, I should have lobbied hard to enact laws to
prevent this travesty. So yeah, being lighter is often a big advantage but
then there are times that being heavier helps keep you from wallowing around
as much as the lighter folks.
Being able to adapt to challenging conditions is an innate part of the sport
(can I call it a sport?) of Fat Biking. As you gain experience, you'll get
much better at putting together micro lines to come up with a ridable route
through seemingly impossible conditions and become adept at subtle weight
shifts from front to rear to avoid bogging down.
When worse comes to worse, just strap a wheel to each foot, and voila:
snowshoes. 
"How come you don't put studs on those
big tires for winter riding?"
Contrary to popular opinion, most snow trails have pretty good traction
because the big tires put a lot of surface area in contact with the snow.
And even a lot of ice has decent traction, especially if it's flat and
smooth, below freezing out, and/or there's a little windblown dust on it.
You just have to ride smoothly over the ice stretches and not try any abrupt
maneuvers.
Most winter XC riding, at least around here in Alaska, is mostly on packed
snow with short stretches of overflow or wind scoured ice. Adding studs
increases rolling resistance drastically, so most riders opt to not use the
studs and just be careful when crossing the occasional ice patches.
There are times, though, when studded tires are life savers: rough, uneven
ice, commuting, very slick ice with water on top of it, etc. I've had really
good success using the 26 X 2.25" Nokian Freddie's Revenz tires on Large
Marge rims. They are slow and sound like a freight train when you're riding,
but traction is great, and they're big enough to offer good rim protection
when hitting rocks or logs. Or if you have a spare set of 29er wheels for
your Fat Bike, Nokian now has a decent 29er studded tire on the market.
There's nothing like bombing down frozen class IV whitewater rivers or
highmarking on icebergs which would be almost suicidal without studded
tires. Just be careful, even studded tires have their limits.
"What's
the deal with the offset rear stays on some Fat Bikes?"
Here's how the offset came about:
-The tires and rims are much wider then a standard mountain bike. This
required the use of a wider chainline so the chain wouldn't rub on the big
tire and wear out the sidewall.
-In order to get the wider chainline, it was necessary to build the frame
with a wider bottom bracket shell for use with a wider bottom bracket
spindle. At the time, most MTBs used a 68 or 73 mm shell with a 113mm
spindle. That wasn't wide enough to clear the tire so we had to use wider
bottom brackets. After a couple generations to accomodate increasingly wider
rims and tires, we ended up with a 100 mm shell and a 145 mm bottom bracket
spindle. So that solved that problem but led to:
-Okay, the front problem was solved but led to a dilemma on the other end of
the drive train: how to carry the new wider chainline back to the rear hub?
At the time, there were very few wider then normal hubs available so we had
to figure out a way to move the cassette out further from the bike's
centerline to match the wider front chainrings using the available 135mm
wide hubs. We decided to create a "virtual wide hub" by offsetting the rear
triangle 18 mm out toward the drive side which brought the cassette out in
line with the front chainrings. So that problem was solved but led to:
-Now that we offset the rear stays, how do we bring the rim and tire back in
line with the bike's centerline? If you were to take a standard rear
mountain bike wheel and stick it in the dropouts, it would not line up with
the centerline of the frame, it would be way out of line toward the drive
side. That led to drilling offset spoke holes toward the drive side of the
rear rim to bring the centerline of the rim and tire back into alignment
with the frame's centerline. This allowed the use of equal length spokes on
each side for a nice strong wheel build. Problem solved, or was it?
-Somewhere along the line, the 29er market started taking off and I realized
that the FatBike geometry was almost identical to the 29er geometry. Why not
build a spare set of 29er wheels to make the FatBike a versatile, year-round
machine? Unfortunately, the 29er rims are skinny and do not allow much of an
offset spoke drilling. I had fairly good luck using a Bontrager offset rim,
but the offset spoke drilling was only a couple mms so in order to make
everything line up, I had to use much shorter (3 mm) spokes on the non-drive
side of the rear wheel to get everything to line up. Not ideal: the spoke
tension was very tight on the nondrive side and very loose on the drive
side. Some hubs had wider flange spacing and I was able to get them to work.
I've been riding the same rear wheel for years with no problems, but again,
it's not ideal. Which led to:
-Ditching the rear offset and using wider hubs which have recently come on
the market. With a 160 mm hub everything works out nicely for chainline.
Yes, they are a little heavier though the Chris King is lighter then many
top 135mm hubs. And for sure, they are more expensive then most 135mm hubs
but look at it this way: it allows your FatBike to be used rear round so
think of how much money you'll save by not having to have two different
bikes. That's why I've kept the 465mm axle to crown length on the rigid fork
allowing a summer swapout to a 29er suspension fork. Losing the rear offset
has the added benefit of making the framebuilder's job a lot easier: much
less chainstay and seatstay bending. And of course, summer 29er wheels build
up nice and strong.
It's
race time!
Go
race, or Go watch!
Alaska is home to some of the toughest
wilderness races on the planet.
Scroll down to see the hot events for this winter, and for
more information about the following winter events click on thier logos
and ride around thier "official" websites.
Susitna 100
a 100 mile bike or ski or run
9am start at Pt. McKenzie General Store.
Little
Su 50k
a 50k bike or ski or run
Iditarod Trail Invitational
a 350 mile bike or ski or run to McGrath and on to
Nome for some.
2 pm start at Knik
Lake, Knik, Alaska
Ice, ice...nothing but a wall of ice and ice carpet!
Alaska Ultrasport racers Mark Gronewald, Rok Kovac, & Bill and Kathi Merchant at the Rainy Pass Lodge during the 2006 race. Alaskan rider Peter Basinger won the 350 mile race on a Wildfire Fatbike.
RaceRStart of the 2009 Iditarod Trail Invitational
Knik, Alaska
