Even in dry conditions, Dan Cheever, store manager of Portland-based BicycleTires.com, contends that on a road bike, tread pattern has no affect whatsoever on the tire's ability to grip the road. Instead, traction is based on how supple the tire is (both casing and rubber compound), tire pressure (lower pressure provides more traction), and width (wider tires get better traction). Road bike tires are generally smooth and tread-free, for these reasons. Well, that and treads increase drag, and we know how you feel about drag, aero-boy.

This system works beautifully in all seasons except winter. Ever felt like you were just out spinning your wheels and going nowhere? Squishy or slippery material like snow and mud yields a low coefficient of friction for a tire without tread. It’s simple physics:

µ = f / N

Where µ is the coefficient of friction, f is the amount of force that resists motion, and N is the normal force. Normal force is the force that your bike tire normally exudes on the pavement. If your bike (with you on it) weighs 176 pounds, then the normal force is 176 pounds. Since we’re talking Newton’s Laws, it would be measured in newtons, not pounds, but you get the point.

The higher µ is, the more resistance there is when two objects are sliding past each other, or in the case of your bike, rolling past each other.

Physics aside, a low µ means there’s not enough traction to move your bike forward. Mountain bikers increase µ by increasing f – the amount of force that resists motion. They do this by using tires with both tread and knobs to provide more bite on loose surfaces.

This same concept can be applied to your road bike in the winter for a safer, smoother ride. If you’re only dealing with wet roads, it may be enough to just select an “all-weather” tire with a stickier rubber compound for improved traction, a tougher casing, one with a higher TPI (threads per inch – 290 is the highest we’ve seen - this allows greater flexion when the tire encounters the salt and grit that accumulates on the roadside in winter), and an additional layer of a material like Kevlar or Vectran for protection against punctures.

But if you commute in really sloppy conditions, or insist on riding outdoors no matter what the weather (both of which we highly recommend), consider winterizing your tires to something beefier and treadier. And no, you can’t just use your mountain bike tires – good idea, considering they’re typically 26mm, but they’re a different diameter and won’t even mount on your road wheels.

You’re probably sporting 23-mm tires on your road bike, which is the most effective compromise between aerodynamics, weight, and rolling resistance. But most road bikes can support up to about a 28-mm tire before there is just no clearance left between the tire and the frame. Deal with the winter slop by bumping up to a 25-mm, or even a 28 if it will fit. (A bit of history for the buffs out there: the 27-mm used to be the typical road bike tire, back when Schwinn was the dominant bicycle manufacturer in the U.S. and established it as the standard tire size. If you’ve got an old Schwinn Varsity taking up residence in your basement, it surely rolls with 27-mm, but those are hard to come by these days).

Before you get out there and crush that slush, remember to purchase new tubes to correspond with your enlarged tires. While it’s possible to run your old 23-mm tubes, it’s not exactly recommended, according to Matt Hayes at Full Cycle in Boulder, Colo., who claims that safety starts with having components in good working order that fit together optimally. Look for 700 x 25, or 28, depending on which size tire you upgraded to.

Your larger tires will provide instant friction, thanks to the larger surface area. As for treads, well, here’s the thing – currently, no road bike tires manufacturers make a “winter tread” tire. The industry perception is that if you’re riding in weather so inclement as to require significant tread, you probably shouldn’t be on a road bike. Doh! Bust out the mountain bike, or if you insist on going swifter, then get yourself a cyclocross bike (and get in on some ‘cross races while you’re at it). But what you can do, besides swapping bikes, is switch from a totally smooth road tire, to one with a bit o’tread. Look closely, and you will find tires with subtle tread patterns. Vittoria, for example, has a special edition tire designed for the Paris Roubaix, aka, the gnarliest road race known to man, called the Pave. Besides grippy rubber designed for wet weather traction, the tire comes in an upsized 24-mm, and features Vittoria’s most aggressive tread pattern – which is barely discernible to the naked eye, but hey, it’s something.

Happy slushing!