Monday, December 8, 2008

 

Wide Tires Are Bad on Snow

From Clayton Cramer:

The source of the C5's problems with traction on snow and ice is the combination of rear wheel drive and very, very wide tires. As the tires get wider, the amount of force per square inch declines. There's roughly 700-750 pounds of force per rear tire--and with the standard tires of the Corvette, this spread over an enormously wide piece of rubber. My measurements suggest that the contact patch is about 30-40 square inches--so roughly 19 psi of pressure. At a certain point, the down force is so little that the tires simply have no hope of getting any grip on either snow or ice.

The way that chains work, and studded tires, is by concentrating the roughly 750 pounds of force per tire into a relatively tiny area--perhaps as little as three square inches for chains--so 250 psi, or a square inch for studs (so 750 psi). That's enough to break a hole in the surface of the ice, and allow you to move forward. Ditto for brakes.

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