Originally Posted by
Lazyass
I measure with my calipers. You don't know that 42"c" means 42 millimeters? Look up the history of bike tire sizing and you'll learn why they put a C on it.
The 'c' is appropriate when referring to the size of a rim; i.e. 700a vs. 700b vs. 700c vs. 700d (only the 700c is in common use anymore). But when you say you measured the tire width as 42c it's pretty meaningless - the measurement of the the width would be in mm, so why not say that you measured it as 42mm?