Rule #40: Tires are to be mounted with the label centered over the valve stem: Pro mechanics do it because it makes it easier to find the valve. You do this because that’s the way pro mechanics do it. This will save you precious seconds while your fat ass sits on the roadside fumbling with your CO2 after a flat. It also looks better for photo opportunities. Note: This obviously only applies to clinchers as tubulars don’t give you a choice.