Safety experts say you should check your helmet before you hop on a bike this summer.
They say many people keep helmets longer than they should and the hot dry weather can make the styrene plastic more brittle.
Bike experts say even worse--some people continue to wear a helmet after a fall instead of throwing it away.
"You get one good crack in it and it loses its structural integrity. It just may not do what it is intended to do and definitely, you're more at risk for a head injury," Doug Barnett of Ruby Canyon Cycles told 11 News on Wednesday.
Helmet manufacturers say a helmet should be used no longer than two to four years and if you get a crack, get a new one.
Also, the fit is crucial. They say the helmet should not slide around and if it does, it could be more dangerous during a fall.