How Slippery Is It?
Technical Discussion of Traction on Ice
How Safe Is It?
What are the risks injury in Icebiking
WindChill
How to figure the Effective Temperature
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Riding
Techniques
Hardpack
After cars have driven over and packed down snow you end up with hardpack. This
is usually still white, but may be anywhere from a quarter of an inch to 3 or 4 inches
thick. Its not quite as hard as ice, but almost.
If relatively smooth, it presents no special problems, other than being slippery.
The other side of that coin is that it usually comes with embedded gravel supplied,
most often, by your tax dollars. This embedded gravel makes it possible to ride
hardpack without studs, as it really does supply ample traction.
There are some down sides, (pun fully intended) to hardpack.
Hard pack can have a smooth as glass surface. More often, you end up with a
certain degree of rutting, caused by cars or bumps caused by footprints that freeze over.
Hardpack on road is often bladed off by road maintenance crews making it skating rink
smooth. If this gets a little water on it it can be really slippery.
Hardpack will eventually melt, making for some of the most bumby riding conditions you
will ever find. Uaually it will break up in chunks due to auto traffic first. Watch
these, as they can be very effective at diverting your front wheel.
 Hard Single
Track
Multi-use trails can become hardpacked and trampled by foot traffic. These are
quite hard to deal with because the foot prints can be quite deep. This leads to an
incredibly jolting ride. Full suspension bikes really help here. Taking the
bumps with as much speed as you can manage sometimes works (especially with studs) as you
don't fall into every hole, you just skim the tops of the bumps.
When hard frozen, there is often enough traction to take these trails at a moderate
speed. They become very difficult to ride when thawing causes them to get wet
and slippery. Nothing but studded tires work then.
Just off of the hardpacked area you may find easier riding, but it may be deeper and
crusty. Try it if you are having problems with the foot-worn portions of the trail.
Ruts
Hardpack on roadways often accumulates ruts. These can be shallow, less than a
quarter of an inch, or very deep, I've seen them 4 inches deep and polished hard as solid
ice.
Longitudinal ruts (running in the same direction you are traveling) are very
dangerous. They will divert your front wheel, landing you on the roadway.
In longitudinal ruts, steering becomes a full time 100% concentration job. You have to
plan every transition from rut-top to rut-bottom. You have to manage your momentum,
not daring to go too fast, but yet needing some speed just to steer.
Tire Pressure
For smooth hard pack, if you have studs, pump them up to the rated pressure. If
there is significant gravel imbedded in the hard pack even regular tires can be ridden
pumped hard.
For rutted hard pack or foot paths, I recommend reduced tire pressure. This will
allow the tires to supply some smoothing to the ruts, and allows the tire to grip the back
side of small ridges that the wheel is still climbing the front side. With hard
tires, you bounce up and over, and generally have no traction on top of the ridge.
Further, lower pressure puts more of your tire tread (or studs) in contact with the
surface. This supplies more traction.
Finally its just plain more comfortable to take hard knobby surfaces with less
pressure.
Much as I dislike rutted hardpack, it does pay to ride around on it to improve your
bike handling skills. There is nothing like it in summer riding other than real
rocky places like streambeds, and they don't even come close.
Techniques
Cross tire ruts as close to perpendicularly as possible. Do not try to steer out
of a deep rut. This risks a wheel diversion. Instead, try jumping the front
wheel out or traveling along the rut until there is a good place to steer out.
Maintain just enough speed to maneuver. Studded tires help quite a bit on hardpack,
and do much to reduce wheel diversions.
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