Somethings been puzzling me
Somethings been puzzling me
I know its not very important in the big scheme of life but something has been puzzling me about wheels.
Why are 26 ins wheels called 26 ins when they only measure 22ins
700 wheels don't measure 700
and 27 ins wheels are not 27 ins
none of them measure their stated size if you include the tyre either
so why are they called what they are?
Why are 26 ins wheels called 26 ins when they only measure 22ins
700 wheels don't measure 700
and 27 ins wheels are not 27 ins
none of them measure their stated size if you include the tyre either
so why are they called what they are?
Have a look on Sheldon Brown's web site. it's all explained there.
http://sheldonbrown.com/tire-sizing.html
http://sheldonbrown.com/tire-sizing.html
- Mrs Tortoise
- Posts: 453
- Joined: 8 Jan 2007, 11:44pm
- Location: Dorchester, Dorset
Jac wrote:Well - I've just read the Sheldon Brown website that Stevew kindly suggested.
It has to be men that devised such complicated 'systems' for measuring wheels and tyres.
Why not just measure the diameter of the wheel - or is that too obvious and simple.
The problem with that is that different tyres on the same size wheel will give different overall diameters, not a big problem on bikes but on a car it could mean the speedo reading incorrectly.
Whenever I fit new tyres to my bikes I always check the settings on the computer just to be sure that it is still accurate to the tyre.
Jac,
Best thing to do is to forget all the 700s and 26 inches etc and just go by the ETRTO sizes that will be on every tyre you see. This is the metric size of the rim, so you are looking for a figure like 28 x 622 or 42 x 559 with two digits and three digits. This system is standardised all through the bike tyre world and although some bike shops wont understand it, most will. Even if the shop doesn't understand you can be sure that you can rely on it if you read what's on the tyre.
The two digit number is the width of the rim and the three digit number is the diameter of the rim where the tyre bead sits.
So as you suggest Jac, someone has decided that it was all too much of a mess and tried to standardise but cyclists being an extremely conservative lot are very reluctant to change and still talk of 27 inch and the likes!!
I recently visited my LBS and asked for a 630 tyre and they didn't have a clue!
Hope this helps.
Best thing to do is to forget all the 700s and 26 inches etc and just go by the ETRTO sizes that will be on every tyre you see. This is the metric size of the rim, so you are looking for a figure like 28 x 622 or 42 x 559 with two digits and three digits. This system is standardised all through the bike tyre world and although some bike shops wont understand it, most will. Even if the shop doesn't understand you can be sure that you can rely on it if you read what's on the tyre.
The two digit number is the width of the rim and the three digit number is the diameter of the rim where the tyre bead sits.
So as you suggest Jac, someone has decided that it was all too much of a mess and tried to standardise but cyclists being an extremely conservative lot are very reluctant to change and still talk of 27 inch and the likes!!
I recently visited my LBS and asked for a 630 tyre and they didn't have a clue!
Hope this helps.