Good advice guys. I'm going to test drive Akstraw's chaulk thing. For what it's worth, (and because I didn't know any better) I have been using the tire pressure recomended for the original bias tires on my 1952 Mercury sedan, for the radials now on it, no problem. I recently drove 125mi mostly highway at speeds up to 65mph, again no problemo! The tires have been on the vehicle at least 20,000 mi.