Huh, am surprised! Perhaps the other tyres I've tried on my Donohue are larger than their states sizes then, as it's nowhere near as tight with Veloflex ones as is current with some Bontrager tyres.
Yeah I think most of them tend to come up larger. I suppose the Veloflex have no rubber sidewall which I expect would add 1mm on an otherwise identical tyre. And those ones I measured are on a 17mm internal rim which is a bit wider than older 700c wheels.
Actually...