Are All Studs Equal?
FIRST: This page is
retained for historical reasons.
Second:, before you go out and spend your money, let me say you
DON'T normally need special rims for regular Commuter ICEBIKING or
recreational winter riding..
The wheels depicted on this page are specialty items, usually used for Off
Road riding, on single track, partially frozen trails, or snowmobile tracks. Most
commuters never encounter the need of these rims unless substantial portions of your route
are on un-maintained trails.
However, for the recreational ICEBIKER the wide rims described here open
up significant new opportunities for exploration and fun in areas you have never ventured,
perhaps not even in summer.
Why Special Rims?
Part of the problem is pounds per square inch (kg per square cm).
Riding on semi-frozen snowmobile trails or single track, or crusted-over lakes, you will
break through the softer portions, your front wheel will sink, and you may do an
Endo. The surface simply can not support the amount of weight you and your bike
At 40 PSI, 200 pounds of bike and rider will we carried on 5 square inches
on the bottom of your bike tires. This will be split roughly evenly between the two
tires. The trouble is, the snow can not bear 100 pounds on just 2.5 sq. inches.
So you sink. You keep on sinking until the amount of tire in contact with the
snow spreads the same amount of weight to more and more square inches of snow.
Once you have enough inches of tire on (under) the snow, you stop sinking.
More square inches on the
The other part of the problem is the shape of the tire. In cross
section, the mostly rounded shape of the typical bike tire causes it to slip sideways
rather than just straight down. Down would be bad enough. Sideways requires
steering input at the very least, may cause falls, and is ultimately unmanageable.
Snow tends to "squirt" out towards the edges of the tire, rather then being
packed down as the tire rolls over it.
A flatter tire cross section
Finally, when on really bumpy hardpack, or other uneven surfaces, high
pressure tires can tend to follow ridges, (diverting you from your intended course), and
bounce, breaking contact with the ground, reducing your traction, and allowing sideways
momentum to be built up while the tire is in reduced contact with the ground. Softer
tires tend to roll over small ridges and bumps, absorbing the bumps by deforming, while as
the same time maintaining contact with the ground.
Lower tire pressure helps.
Each of the above aids to off-road winter cycling has its own place.
On rutted ice, lower pressure and a flat cross section are better. Glare ice
calls for higher pressure. All three at once would be ideal for many off road
situations in winter.
The only way to get all three at the same time is to run wide
tires with a flat cross section at low pressure.
The problem is this is virtually impossible with a narrow rim, because if
you lower the pressure enough to get a flat cross section you run the risk of snake bite
(pinch flats) as the rim will bottom out inside the tire. Additionally, much of the
tires potential width it "consumed" by having the tire form a circle (in cross
section). If the tire only had to form half of a circle, it would be a much
wider circle. If you have ever spread a bike tire flat (pulling the beads away from
each other) you were probably amazed how wide it was.
A Brief History of the
Snow Cat Rim.
I designed the Snow Cat for snow riding but there had been hints of interest in them
for downhill racing from the beginning, so I didn't go ultra-light on the cross section.
That turned out to be a good idea. For a few years DH sales exceeded winter sales. I
started doing serious promotion at major DH events about five years ago and spent the next
few years watching over my shoulder for the big companies to pick up on the idea and crush
me. It took a surprisingly long time.
The bike industry is cash starved and very conservative. DH rim widths crept upward for
a few years with Sun, Mavic and a few others watching each other and giving out BS reasons
why really wide was a mistake.
Yet, people from the big rim companies would tell me they were glad I was making such
wide rims because it took pressure off them to do it. I got lucky when Sun's first really
wide rim (Fat Albert) flopped. It was fun being on the right side of the rumor machine.
My product worked, the big company's knockoff didn't, consumer accounts about why it
was bad were wild and widespread.
Nokian tire designer Jorma Tikka got interested in DH and came up with the idea of a
tire sized to really fit on the Snow Cat. Nokian took a bigger chance than I've seen any
other large company do in the bike industry. They made a three inch tire (the Gazzalodi)
when there was only one rim and NO BIKES to fit it. They introduced it at the '98 Winter
X-treme Games. Within a few weeks there were plenty of bikes to fit it. I was swamped with
calls from small DH frame builders wanting to know dimensions. The standard changed
So the little kitty led the DH world onto big rims and big tires. Eventually they got
it right and there are now wide rims more suitable for DH than the Snow Cat.
But the monster rolled right past me and I didn't get
crushed. DH rims are very heavy, so the Snow Cat is the lightest of the big rims. Disc
brakes are the standard for DH so very few of the wide rims have brake surfaces.
The market isn't big enough for even one winter rim. I could only get it in production
by doing silly, egotistical things with larger lumps of money than I should have. God
bless the oil economy. Rim manufacturers are smarter than I am and don't seem to want to
waste capital on a product with such limited appeal. So they try to do double duty with a
DH rim. We'll see where it all goes but I'm not afraid of competition. I took last winter
off; went away and did no marketing and had no product. It would be amazing if no one
tried to move into the (small) void.
One more thing I like about Snow Cats: I can drill them in any crazy way anyone wants
(see photos) even, (gasp), dishless rears. I mean really dishless, with identical spoke
angles and tensions on both sides. This is how Charlie Beristain (pictured below)
just got his. (You can see the offset spoke holes in the side-by-side pictures
below). Ritchey may have "invented" OCR but I'd been making 0-dish Snow
Cats for years before he did. Standard width rims can correct for dish by a few mm. Only a
big flat rim lets you shift the (w)hole pattern the 10 mm needed to completely compensate
for eight or nine gears.
Simon Rakower All
The Wide Rim Solution
These are exactly the conditions that Snow Cat rims
were designed to meet. Designed by Simon Rakower of All Weather Sports in
Fairbanks Alaska, the Snow Cat rim is 44mm wide, compared to 22mm
or 32mm for normal mountain bike rims.
There are several other companies making wide rims for downhill races.
Cats, these were not designed with winter cycling in mind, and may be heavier. They are, however designed to take a beating and have similar width.
This extra width of wide rims provides for a flatter cross section to any
tire mounted. This widens the contact patch, puts more square inches on the ground,
meaning you can reduce pressure and still carry the same weight.
Further, with wide rims, the rim edges sits directly above the side wall,
or, in some cases, outboard of the tire altogether. (See photos below). This
reduces the risk that the your rim will bottom out inside the tire. Instead it will
be riding above the sidewall of the tire. Hitting a bump with wide rims is far less
likely to cause a pinch flat.
This means you can reduce air pressure even further. Reduced air pressure
brings more tire in contact with the snow, as the contact patch is elongated (front to
Wide rim spreads tire, flattening it's profile and positioning rims directly above side
wall. Snake bite (pinch flat) is less likely.
With regular rim, tire bulges out from both sides of rim. Hard bumps will drive rim
down "inside" tire when run at low pressure. This can cause snake
With more inches in contact with the snow, you are able to spread that same 100 pounds
per tire over a greater area. At 10psi, the contact patch would be almost 10
square inches per tire. This is well within the load bearing capabilities of some
snow surfaces, such as snowmobile trails, and slightly packed areas. With lower
pressure, down to 5psi you might come close to 20 square inches per tire. Although
you can reduce air pressure to as little as 5psi with ride rims, most riders maintain
closer to 12psi as their minimum.
Some riders report less control on glare ice surfaces when riding with
real low pressure. This is not a problem caused by wide rims, just one you are not
likely to run into until you have wide rims.
When you lower tire pressure, you also lower the amount of pressure on the
studs. This is offset by bringing more studs into contact with the ice.
However, at some point (around 5 or 7 pounds from all reports) you get so little weight on
the studs that they do not dig into the ice at all. They simply skate on top of the ice,
providing less traction than rubber tires.
On bare ice, it has been found that studded tires should be run at near
their sidewall pressure, but you want to still show some sidewall flex while riding to
reduce tire-bounce. Tire bounce can happen by hitting even small bumps with tires
inflated quite hard. Normally not a problem in summer, but in winter when the wheel
loses contact with the ground it may come down with a slight sideways momentum and slip
out from under you.
Additionally, there can be problems getting wide rims to fit on your bike.
The front is seldom a problem, but the rear can be too narrow where the chain stays
join the bottom bracket, or near the bridge on the seat stays.
|In addition, it is hard to build a wheel with a wide rim and not end up
with an excessive amount of "dish" in the rear wheel while trying to fit the
gear cluster and the wheel inside the chainstays.
Many Snow Cat rims are drilled for
off center spoke holes for the back wheel. This allows construction of a wheel with
less "dish" than would otherwise be necessary, and provides the needed clearance
and centering of the rear wheel.
Note that since these rims are usually used with quite low preasure, the plastic liner
is all that is needed to keep the tube from protruding through the holes shown in this
shot of the Snow Cal "SL" model These holes save over 600 grams per set of
There are also problems with getting brakes to work correctly. The rim is so wide
that modification of the brake arm mounting and or the brake pads may be necessary.
Some brake arms can actually give greater clearance when mounted backwards, as carefull
study of this picture shows. Those brake arms are designed to have that curved
portion of the lever faceing the tire. By reversing each lever, more clearance is
||For this reason Disk Brakes and wide rims
are often found on the same ICEBIKE. Click here for a detail shot this bike's real wheel.!!
Finally, wide rims and studded tired can add as much as 4 pounds to your
bike over the weight of your regular rims and tires, especially if you end up using
down-hill rims. Much of this weight is attributed to the studded tires. If
riding of packed snow, you may not need them.
Wide rims provide all three of the desirable
attributes needed for winter snow travel. They still do not provide adequate
"flotation" to allow you to ride on top of powder snow or even heavy wet
snow. However, snow that has thawed and refrozen, or been rained on is often firm
enough to ride with wide rims and the proper tires. Winter snowmobile trails often prove
quite navigable with wide rims.
Additionally, in loose snow, wide rims provide a greater measure of
control, as the tires tend to wallow less with a flatter profile, and the reduced pressure
keeps more tire in contact with the ground, (and more studs in contact with the
ice). Handling is greatly improved, as is your speed over the ground. Some snow
terrain is simply impossible without wide rims.
If you spend much time off road in winter you will likely sooner or later
find your self on wide rims. They are virtually required equipment in some off-road
races such as the Alaskan Iditasport, and add greatly to the capabilities of your bike on
Photo Credits: Charlie Beristain, John Andersen, and Simon Rakower.