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Adam Smith installs a studded tire on one of the many customers that poured into the Oregon City Les Schwab store in this 2004 photo.

(The Oregonian/File)

Oregon and Washington drivers using studded tires will need to swap them out before Friday or face a hefty fine.

Tires with protruding metal studs are allowed under state law between Nov. 1 and March 31. The season can be extended, but the Oregon Department of Transportation said weather forecasts offer no reason to delay.

Using the tires out of season can come with a $200 fine in Oregon. That's because the tires grind on roads, costing Oregon $8.5 million a year in premature repairs to state roadways, according to the state transportation department. They also leave ruts in the roads that can contribute to slick conditions in wet weather.

At one time, 16 percent of Oregon drivers used studded tires, but transportation department study found that number had fallen to 4 percent in 2014.

Previous efforts to ban studded tires in the state, or to limit their use, went flat. The state has taken to encouraging drivers to use rubber traction tires, which perform nearly as well as studded tires on ice but better in other conditions, including snow, slush and dry weather.

-- Elliot Njus

enjus@oregonian.com

503-294-5034

@enjus