Why do some bicycles have so many gears?
Actually, you can’t use all the gears in a bike. That means you shouldn’t cross chain (use the leftmost gear at the front ant the rightmost gear on the rear, or viceversa). So a 27 spd mountain bike will likely have only 13 or 14 usable gear combinations. Having this range will make the bike adapt better for the type of riding you’re doing at any single time. If you’re on a long climb you could use a low gear, but if you want to clear a short steep climb, probably a mid-range gear would let you stand up and hammer. Or if you’re on paved roads you would want a larger gear. About mountain bikes, most bikes comes with the crankset with 3 gears and on the rear with 7, 8 or 9 speeds. Mostly, the largest gear at the front is seldomly used. Some bikes go with only 2 or a single gear up front, depending again, of the type of bike (freeride bikes usually replace the largest front gear for a bashguard, and downhill bikes usually have only a single gear upfront with a chain guide). Most mid to hi
