Why wear a helmet? Good question. A national survey on bicycle-helmet use by the Consumer Product Safety Commission estimates that more than 40 percent of cyclists never wear them, though the CPSC has also suggested that doing so can reduce the risk of head injury by 85 percent.

Superman! Not.

That's even more important than it sounds, because cyclists hospitalized with head injuries are 20 times as likely to die as those without, according to a monograph by the Johns Hopkins Injury Prevention Center, sponsored by the Snell Memorial Foundation and distributed by the Bicycle Helmet Safety Institute. Head injuries in cyclists are seen in 65,000 emergency-room cases and 7,700 hospital admissions annually, the monograph adds.

Of course, you might not even make it to the hospital after stacking it sans brain-bucket. The U.S. Department of Transportation's Fatality Analysis Reporting System estimates that 98 percent of the bicyclists killed in 1998 were riding bareheaded. And here you thought all those absent training partners had taken up golf.

	Care Much About Your Head? Read more about bike safety. Got any thoughts about wearing a helmet . . . all the time? Ever been in a bike accident? They happen.

First, call a bike shop and a hospital and inquire about the respective costs of a bicycle helmet and brain surgery. Should any nagging doubts remain afterward, try banging your bare head on the sidewalk a few times, really hard.

If it feels good, it's probably too late for you to waste hard-earned money on cranial protection. Fill out a living will and plunk a few bucks down on a nice cemetery plot instead.