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Old 09-03-08, 08:07 AM   #1
TexasKid
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Tire size question

I have several bikes. One has 700x32c tires. Another has 700x38c. The 700x38c tires are slightly smaller than the 700x32c tires - I mean the circumference of the tire, as if you're putting the tire in your palm and wrapping your fingers around it and touching your fingers and thumb. Know what I mean? I thought 38's would be bigger than 32's. What do I not understand about tire sizing? Thanks!
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Old 09-03-08, 08:20 AM   #2
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Many tires are not "true" to size labelled.

Best to actually measure with something caliper like, for accuracy.

Are both tires on the same width rim?

Are they both carrying the same pressure?

Variables abound....
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Old 09-03-08, 11:24 AM   #3
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Actually, the "38c" part really only refers to the width of a tyre. The cross-section profile of a tyre isn't always perfectly round. You can have a wide squat tyre, like the Tioga CitySlickers which are modeled after a motorcycle tyre. It is roughly 1.5 times as wide as it is tall. On the other extreme, you can have narrow-profile time-trial type tyres that are about 0.8 times as wide as they are tall.

Pull out the calipers and measure the actual casing-width. The rubber part doesn't count. May be tough on some tyres due to the knobbies, but you can usually wedge the calipers in between them.
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Old 09-03-08, 12:11 PM   #4
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Thanks, Now I'm totally confused. I'll read up on this and if I'm still feeling totally ignorant, I'll post another thread. Looks like someone else posted a similar topic right before me.
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Old 09-03-08, 04:59 PM   #5
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Yes, they did, use that link I posted there to learn the same stuff I learned.
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Old 09-03-08, 05:00 PM   #6
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Here I feel good today: http://www.sheldonbrown.com/tire_sizing.html
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