Sacrificial helmet or not
Posted by: pikabike on Oct-23-12 5:38 PM (EST)
Bike helmets are a sacrificial layer of protection. One hit and the helmet has done its job already.
Paddling helmets may have to protect against multiple hits in just ONE outing, never mind on other days.
Also, bike helmets are designed for impact protection, not necessarily pierce-through resistance. Remember the ultralightweight foam Giro helmets that you covered with a lycra half-dome? Yeah. Those have been replaced by helmets that all have at least a thin hardshell, but some of the shells don't feel like they'd protect against a sharp pointy object. Not to mention all the venting holes and slots in bike helmets! Paddling helmets' shells are thicker and very hard.
I don't know this, but I would guess that rock climbers' helmets have to protect against falls from much greater heights than either cyclists or paddlers incur. And those helmets are probably heavier for this reason.