Using tire durometer

[ssanto]

I've got a stack of 12 used wheels and Goodyear NASCAR racing slicks. I've got 4 on the car and I've got room for a stack of 6 in the garage. That means I have to put two up in the attic. I know that's not the best environment so I want to pick the two worst ones to stick up there.

I got a Longacre tire durometer and I'm having trouble getting repeatable results.

Question... Does it matter if the tire is inflated? Would the pressure in the tire pushing it outwards affect the reading? Or is it just the same as doing it to an uninflated tire?


Thanks,
Sal