Originally Posted by jputnam

Most cars are designed to keep the weather out. Weatherstripping, door seals, galvanizing, undercoating, anti-corrosion primers, etc.

I've been riding year-round in Seattle-area rain for so long I don't really consider the forecast unless we're in danger of snow or ice. My bike has fenders, mudflaps, a chain guard, and a packable set of rain gear that stays in the saddle bag year-round, because we can get cold rain in August.

Many racing-inspired bike parts have pretty lousy weather sealing, they're the equivalent of old MGs that were fun in dry weather but constantly damp if driven in the rain. Some road bikes will actually fill their bottom brackets with water when riding in the rain -- water seeps in higher on the frame and accumulates at the low spot.

Things have gotten a lot better for the average non-racing consumer since mountain biking became popular -- plenty of reasonably-priced components designed to resist water and mud.