Generally....the rear tire has it's valve stem on the brake side this is to keep you from getting grease on you from the sprocket when checking tire pressure). But on SOME models, they did put it on the sprocket side. It's really kind of hard to screw this one up. The brake rotor bolt holes are samller than the sprocket bolt holes and the tire has an arrow on it, showing direction of rotation. So if you have the sprocket and rotor on properly, and the tire going in the right direction, it doesn't really matter what side the stem is on.
