Rim Sizes?

It should be mentioned (since it was kind of implied earlier) that a 700c tire IS NOT the same as a 27 inch.

27 inch is a 630mm diameter
700c is a 622mm diameter.

(this is bead fit diameter, btw)

On road bikes with tight fits (like a 700x20) that’s a huge freakin’ difference.

a 26 inch tire is the same as a 650c, however.

in case you don’t believe me:


ISO Bead Seat Diameter	Traditional Designations
635 mm	28 x 1 1/2
630 mm	27 x anything
622 mm	700 C
599 mm	26 x 1.25, x 1.375
597 mm	26 x 1 1/4, 26 x 1 3/8 (S-6)
590 mm	26 x 1 3/8 (E.A.3), 650 A
587 mm	700 D
584 mm	650B, 26 x 1 1/2
571 mm	26 x 1, 26 x 1 1/2, 26 x 1 3/4, 650 C
559 mm	26 x 1.00- x 2.125
547 mm	24 x 1 1/4, 24 x 1 3/8 (S-5)
540 mm	24 x 1 1/8, 24 x 1 3/8 (E.5), 600 A
520 mm	24 x 1, 24 x 1 1/8
507 mm	24 x 1.5- x 2.125
490 mm	550 A
457 mm	22 x 1.75; x 2.125
451 mm	20 x 1 1/8; x 1 1/4; x 1 3/8
440 mm	500 A
419 mm	20 x 1 3/4
406 mm	20 x 1.5- x 2.125
390 mm	450 A
369 mm	17 x 1 1/4
355 mm	18 x 1.5- x 2.125
349 mm	16 x 1 3/8
340 mm	400 A
337 mm	16 x 1 3/8
317 mm	16 x 1 3/4
305 mm	16 x 1.75- x 2.125
203 mm	12 1/2 X anything.
152 mm	10 x 2
137 mm	8 x 1 1/4

Info also stolen from: http://www.sheldonbrown.com/tire_sizing.html
'cause he’s awesome and his website taught me how to fix bikes oh so long ago. swoon

For a reference table of tire (tyre) sizes, try this link. It’s the UK National Cyclists` Organizations website that has the most complete chart I’ve seen anywhere; it’s even got more the Sheldon Browns! With a discussion of tire compatibility, how tires are measured, recommending the use of ISO ratings, as well as minimum pressure recommendations (for road use). For instance, a 26×1½ is a whole inch bigger than 26×1.5.

By the way, did you know that a Coker tire (which is not on the chart, by the way :astonished: ) is not really a 36 inch tire? I measured mine and the 36 inch measurment seems to be the overall diameter, not the rim as with most other tires.

ah? here we go, just like i predicted earlier… :astonished:

the 26 inch rim size used on unicycles and mountain bikes is not the same as the 650c size used in time trialing bikes…arg! stop the bleeding!

Pretty much all tire sizes are based on the outer diameter of the tire, more than the rim size. The rims are always smaller than their nominal “size.” For example, 24" rim is somewhere around 22" diameter. Further confusion for people trying to figure out what size things are.

So there’s the size marked on the tire, which is in most cases close enough. Except for the exceptions. Kind of like the English language.