The quick and simple way to know the rim size is to try a tire on it. Find a 26" tire, easy because they are so common, and try mounting it to the rim. If the tire goes on it's a 26" rim, if it won't it's a 650. Simple as that.
Tom HarrimanSan Francisco, Ca
> Date: Tue, 11 Jan 2011 19:49:14 +0000
> From: firstname.lastname@example.org
> CC: email@example.com
> Subject: Re: [CR] How to ID a rim: 650b vs 26"?
> On 1/11/2011 6:19 PM, Eric Elman wrote:
> > Hello List Friends,
> > I have three NOS Mavic Mod E rims that have no size markings on them. Can anyone advise what/where to measure (please be very specific) and the dimensions I should look for for in order to determine if they are 650b or 26"? They are not 700c just based on size comparison to numerous other 700c rims I have in my stash.
> > Thanks in advance,
> > Eric Elman
> > Somers, CT USA
> Start with ETRTO sizing which is logical
> beaddiameter for a 650B tyre is 584mm, 650C = 571mm, 26" MTB is 559mm.
> With an inch at 25.4mm, it shouldn't be to difficult to keep them apart
> Marten Gerritsen
> Kiel Windeweer