# Singlespeed & Fixed Gear - Need help understanding tire sizes.

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Airbrushkid
07-01-12, 10:23 AM
I have a pair of 700c X 23c and a pair of 700c X 45c. I have notice the the 45c tires are taller by about 1". So how can I tell when buying other 700c tires with different widths how much taller they are?

Thank you for any help.

Retem
07-01-12, 10:34 AM
http://sheldonbrown.com/tire-sizing.html
above is an article on tire sizing
as a general rule 23~25 are about 1-1.25" wide at the tread
side wall isn't really taken into consideration

Airbrushkid
07-02-12, 07:51 AM
So there's no way to determine the actual outside diameter of the different width tires until I buy each one?

Canaboo
07-02-12, 07:55 AM
So there's no way to determine the actual outside diameter of the different width tires until I buy each one?
Seems like the depth increases fairly proportional to the width increase.

prathmann
07-02-12, 08:32 AM
So there's no way to determine the actual outside diameter of the different width tires until I buy each one?
When inflated the tires cross-section is fairly round. So in principle the 23mm tires would have an outside diameter of about 622mm (diameter of rim) + 2 x 23mm = 668mm or 26.3" whereas the 45mm tires would have an outside diameter of 712mm or 28". But in practice the actual widths vary some between different tire makes and models and it'll also vary a little depending on the width of the rim on which the tire is mounted

hockeyteeth
07-02-12, 09:05 AM
Well, I know the E.T.R.T.O. labels display bead seat diameter and width, but I am only familiar with height (which would be like "profile" or "aspect ratio" in automotive tires) displayed on high-end mountain bike tires.

Amusingly, here's an official complaint form on tire size discrepancy: http://www.etrto.org/page.asp?id=1727&langue=EN

hockeyteeth
07-02-12, 09:07 AM
When inflated the tires cross-section is fairly round. So in principle the 23mm tires would have an outside diameter of about 622mm (diameter of rim) + 2 x 23mm = 668mm or 26.3" whereas the 45mm tires would have an outside diameter of 712mm or 28". But in practice the actual widths vary some between different tire makes and models and it'll also vary a little depending on the width of the rim on which the tire is mounted

This will vary by width of rim used. Ever put a skinny road tire on a wider hybrid-type rim? You'll notice the tire lays much flatter and you can sometimes touch the rim to the ground when cornering sharply.

Airbrushkid
07-03-12, 09:04 PM
Thank you everyone. It is just messed up when you get a tire that says it's a 45c width and it is actually a 43.5c.