This is more reference to myself, but others may find it useful. Here are the measured diameters of the bike tires which I own:
· Continental Travel Contact (26″ x 1.75″ / Wire Bead) @ ~55psi: 2027mm
· Specialized The Captain Control (26″ x 2″ / Aramid Bead) @ ~40psi: 2110mm
· Specialized Fast Trak LK (26″ x 2″ / Wire Bead) @ ~45psi: 2104mm
· Nokian Hakka W300 (26″ x 2.2″ / Aramid Bead) @ ~35psi: 2099mm
· Kenda Nevegal (29″ x 2.2″ / Folding) @ ~40psi: 2303mm
· Specialized The Captain Control (29″ x 2″ / Aramid Bead) @ ~30psi: 2285mm
· Schwalbe Racing Ralph (29″ x 2.4″ / Folding) @ 27psi: 2316mm
· Nokian Gazza Extreme 294 (29″ x 2.1″ / Wire Bead @ ~30psi: 2278mm
In case you are wondering why I’d measure this, these numbers are needed in order to calibrate a bike computer so that it may be reasonably accurate in measuring speed and distance.
The measurement was taken by rolling the tire (fitted to the wheel and inflated as listed) along the basement floor and measuring with a metric tape measure. Yes, I know the diameter will vary some as the tire is slightly flattened while rolling, but finding that variance will require some long distance straight line riding with a GPS and then a comparison. I may do that later on the smooth tires (Travel Contact), but not on the knobbies.