Excellent question. As someone who has twice dodged severe head injuries because of my diligent wear of a bicycle helmet, I’m pretty sensitive to this topic.
And you raise the exact point—what effect does sweat and the sun have on a helmet? And the answer is this: Quite a bit. Sweat and the salts it releases are acidic and corrosive, even eating away at plastic. And the sun is simply brutal on plastics, which is why any pack you wear for a few summers will start to fade (and the fabric greatly weaken).
So what to do? You can take a few steps to prolong the life of a helmet. Every other week or so, dunk it in a bucket of cool water and swish it around some. That will help clean out dried sweat. And of course, try to store it out of the sun, someplace dry and cool.
Otherwise, I really recommend getting a new helmet every other year or so, if you’re a real consistent rider. Otherwise, every four years. I mean, why take the chance? Even if it looks fine, it will have been weakened by the elements. And of course, any helmet that has suffered an impact should immediately be taken out of rotation. After all, a decent helmet is exceedingly cheap insurance—under $100, unless you really want the latest and sleekest.
If you are due for a new lid, these are my picks for the best, most affordable helmets out there for every biking style.
Road Biking: Giro Savant
It’s true you can easily spend $180 and up for a road helmet. But for good protection you don’t need to.
So take a look at Giro’s Savant ($90). A few years back it would have been the top of the Giro pecking order, now it’s just a great value in a light, 25-vent helmet. I like Giro’s “RocLoc” fit and strap system, and of course the Savant meets all current standards for head protection.
The Alternate: Of course, you can splurge as well—on a Mavic Plasma ($160). This is a very hot-looking helmet, but one with enough venting to keep you plenty cool. Plus it has exceptional fit, and a removable visor.
Mountain Biking: Bell Sequence
Mountain-biking helmets really are different from road helmets.
Mountain helmets typically have more venting at the top of the helmet, so warm air can escape when you’re grinding up a long slope in the big ring. So take a look at the Bell Sequence ($80). It’s an excellent all-around mountain helmet, with plenty of ventilation and a removable visor.
The Alternate: Here’s a new take on the trad MTB helmet: The POC Trabec ($150). The Trabec inherits features from POC’s ski helmets, such as a more all-head fit than some other helmets, which tend to sit on top of the skull. Plus it’s a very cool-looking helmet.
Urban: Bern Brentwood
Not everyone wants a "bike" helmet. So try one of these.
Bern’s Brentwood helmet ($80) works fine on bikes, but also gives you good head protection for skateboarding, skating, skiing, or anything else. It’s close-fitting and subtly designed, so doesn’t look like a fighter jet has landed on your head.
The Alternate: The ProTec Classic Skateboard Helmet ($33) is unlike some other skateboard helmets out there—it actually meets the same safety standards as bike helmets. It has a soft foam liner, ABS shell, stainless steel hardware, and a sleek look that’s perfect for the streets.