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confused about tire sizes?(6 posts)

confused about tire sizes?Gall
Oct 3, 2001 3:20 PM
hello again...

today i got a pair of 28mm conti top tour 2000. when i put them on they looked really narrow. when i measured them with my caliber tool i got 24mm. i went and measured my conti GP 3000 on my "good" road bike and got the same measurement!

could someone please explain this to me

Oct 3, 2001 3:23 PM

He says it all.

re: confused about tire sizes?Gall
Oct 3, 2001 4:11 PM
this might sound stupid but do the tires flatten out as they are used... making them "wider"???

do any of you all use tires like this on dirt roads?
No.Kerry Irons
Oct 4, 2001 4:54 PM
What possible physical mechanism could be proposed that would cause a tire to widen with wear? The only thing that keeps a tire's shape is air pressure, and that shape will always be round unless the casing stiffness is greater than the tire pressure. That would be hard to imagine.
not the same number!!Rusty McNasty
Oct 4, 2001 7:54 AM
That 28 on your tire (clincher) is not a width measurement, but a height measurement! That way, you can get the diameter of the entire wheel. 622mm + 2*28mm = 678mm.
The only time that # is supposed to be a width is when the tire is in inches (27x1 1/4), or on tubular tires, where the 2 digit # is usually very accurate
Oct 4, 2001 2:57 PM
but bear in mind that the two measurements are usually coincident: ie, the tube always inflates the tyre to a perfectly round cross section. A little extra tread thickness may make a difference, but nothing else will... 28mm high (off the rim bed) usually means 25-28mm wide.