The recent winter-like conditions that have swept through Northern California are a good reminder to travelers to check their tire tread.

A recent government study of more than 11,000 passenger vehicles found that 10 percent of them had at least one bald tire.

Wet roads and rainy weather make braking and handling much more difficult, and Consumer Reports says that will have the risk of accidents going way up.

That's why Consumer Reports' auto engineers recently tested tires on a wet track. The test is for hydroplaning, which is when the vehicle hits a puddle of water, and the tires lose their grip on the road.

"You start to lose steering feeling, steering control, and you just go straight ahead no matter how much steering you put into the car," said Consumer Reports Gene Peterson.

The test car that had brand new tires did fine navigating the hydroplaning course. Then Peterson and Consumer Reports' Jennifer Stockburger replaced the new tires with ones that had only half their tread and repeated the test. This time, Peterson hydroplaned and hit the course cones.

"You can see with new tires that have their full tread. They have a lot of slots, which provide spaces for water evacuation and biting edges. But when the tires start to lose their tread depth, many of those slots disappear, and you have nowhere for water to go or to give you a biting edge in snow," Stockburger said.

When Consumer Reports tested the half-tread tires in the snow, the engineers found they had a lot less traction. And in braking tests on wet pavement at 40 mph, the half-tread tires took three to six feet longer to stop.

Consumer Reports says that if you drive a lot in wet or snowy weather, you're better off replacing your tires well before they're completely worn.

To check your tires, you might want to pick up a tread-depth gauge sold at auto parts stores for about $5.