A guide to buying a bike helmet

You shouldn't travel very far on that new bike - whether it's off to school in a few weeks, around town for some errands or on one of the city's bicycle trails - without the right helmet.

"If you're going a block from your house, you should always wear a helmet," said Dave Forsyth, owner of Dave's Bike Infirmary in Milton, Mass.

Whether you're an experienced cyclist or a recent convert, you shouldn't assume that a hand-me-down helmet will protect you in a crash.

Jim Quinn, owner of The Bicycle Link in Weymouth, Mass., said riders should replace their helmets every five years. During that time, the inner polystyrene padding can deteriorate, making it less effective at absorbing the shock of a collision.

All new bike helmets must meet specific safety requirements set by the U.S. Consumer Products Safety Commission.

That government standardization means you don't have to shell out a lot of money for safety. The price of helmets has dropped substantially in recent years, Quinn said.

Base models that used to sell for $85 eight years ago now go for about $45, he said. They can provide similar protection and ventilation as more expensive helmets.

Serious mountain bikers may consider a model with a visor and extra coverage for the back of the head, Quinn said, but most helmets provide sufficient protection for all riders.

Still, even the most advanced protective headgear won't save you in an accident if it doesn't fit correctly.

A helmet should always rest comfortably on your head, without pinching or blocking your field of vision, Forsyth said. Many newer models are "one-size-fits-all" and can be adjusted to fit most head sizes. But Quinn said shoppers should still try them on before making a purchase, preferably with a knowledgeable salesperson.

Wear it well

Quinn offers these tips for buying and using your bicycle helmet.

• Bicycle helmets generally come in three sizing categories: toddler (ages 2 and 3), youth (ages 4 to 12), and adult (ages 12 and older).
• If it fits properly, your helmet should rest right above your eyebrows and just over your ears.
• It's called a chinstrap for a reason: The buckle should rest snugly under your chin, but not so tightly that you couldn't swallow a gulp of water. If you do it correctly, the strap-adjustment buckle should hang under your earlobe.
• Don't wear your helmet like a hat. Make sure that it sits evenly atop your head, and isn't tilted forward or backward. A pushed-back helmet won't provide any protection if you fall forward, the most common kind of bicycle accident.
• Resist the urge to buy your child a big helmet in the hopes that he or she will grow into it. Children's heads don't grow as fast as other body parts, so the potential savings are minimal - especially when compared with the added risk of injury from wearing a too-large helmet. 

Photo: Gary Higgins/The Patriot Ledger -- Sam Pollock, manager of The Bicycle Link in Weymouth, Mass., shows a line of bike helmets.