Radial Location of a Bicycle Tire
From Pvdwiki
Attention to Details
A bicycle tire should be mounted so that the markings on the tire can be read, from both sides if possible, at the valve. This is so that the valve can be located as quick as possible in a race situation.
An Argument Against This Logic
For a trail rider, it may be better to mount mount the markings that exist on one side of the tire at the valve so that when a flat occurs, the location of the flat can be located on both the tire and the rim. This assumes that one side of the tire looks different than the other.
Trail Style: