Originally Posted by
Sy Reene
Random thought.. is a tire's width-as-measured best defined as ideally the inside carcass width, vs. just taking a caliper and measuring the inflated tire? Reason I ask is for example, some tires have the thicker tread (that runs down the center) extend and wrap further around the tire toward or all the way(?) to the bead. Some tires only have the thick center tread on the tops of the tire and a caliper wouldn't be touching this section when doing a measurement.
If the heavier tread thickness could be eg. 1mm thicker than sidewall thickness, and doubling that when measuring a tire's inflated width, could be inadvertently adding comparatively 2mm to one tire vs. another. Maybe an example is a Gatorskin vs a GP5K ? Both have the exact same 26mm measured width according to BRR's site, but is one including a bunch of protective rubber, while the other is not. From an inflation/PSI perspective, is the GP5K more air than a Gatorskin. The default conclusion being that the Gatorskin should be inflated to a higher PSI ?
They're measured as mounted.
As for your example, I wouldn't worry about it. a) big whoop - you're going to take inflation recommendations with a grain of salt, anyway, given preference, road conditions, gauge inaccuracies, etc b) in your scenario, the extra tread thickness would also result in a less supple casing, probably making up for the small psi recommendation difference and then some.