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My other half had a blowout today on her vintage ladies bike. The tyres are all cracked and dry so it was inevitable eventually.
No problem I thought..I'm a bicycleist. I can fix it!
Only, the wheel is some crazy old fashioned thing from like, when I wasn't even born and shit..
The tyre that came off there has written on it thus, 40-584 (26 x 1 1/2) - N716
Two bike shops couldn't help with the exact size, but I came away with a tyre that was a 26 x 1 3/8. I thought 3/8 is a smidge under 1/2" so it'd probably be fine, thinking that the 1 1/2 relates to the width?
It doesn't fit anyway. But, it doesn't fit in an unexpected way. Seemingly the tyre is a little too big in diameter and will not hook into the rim. When I try to inflate it kind of expands off the rim.
The rim itself measures 23 1/2" inches, or 600mm in diameter. The old tyre measures just under 26" outer diameter.
I is confused. I tried to read a bit of Sheldon Brown's site but quickly glazed over.
Can anyone shed any light? 👍
Yeah, I googled the numbers too, but take those tyres for example. They're both 27.5". The tyre that came off is 26".
The new tyre I'm trying to fit that doesn't fit is 26".
Hence the confusion.
Ignore the 26” 27.5” thing
If you just go by the ISO numbers
The 40-584 is the important bit
https://www.cyclinguk.org/cyclists-library/components/wheels-tyres/tyre-sizes
And yes shock horror 27.5” is not a new thing after all
Organisation (ISO) in addition to more familiar markings. The ISO size comprises two numbers separated by a dash. The three-digit number after the dash is the more important. This is the bead diameter at which the tyre fits onto the rim.
Thanks Orangeboy. Very helpful article. I'm glad that confusion about wheel size is a thing... 😊
Reading off numbers is one thing, but understanding what they relate to is another 👍
584 is a 650b, not an imperial size tyre. Is the bike French by any chance?
The tyre you have bought is for a 590 rim.
You shouldn't have any problem getting a suitable tyre, 650b is a common size.
(There's about 5 different rim sizes for 26" tyres, ranging from 571 to 597)