Somethings been puzzling me

Jac · Post by **Jac** » 3 Feb 2007, 5:25pm

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?

Post by **Mick F** » 3 Feb 2007, 5:42pm

Gordon only knows!

Just done some measuring ....

My 27 inch wheels measure 27 inches including the tyre.
My 700c wheels measure 670mm including the tyre.
I don't have a 26er to measure!
????

Mick F.Cornwall

stevew · Post by **stevew** » 3 Feb 2007, 5:52pm

Have a look on Sheldon Brown's web site. it's all explained there.

http://sheldonbrown.com/tire-sizing.html

Dai · Post by **Dai** » 3 Feb 2007, 6:52pm

Presumably the measurements were done by one of us blokes - you know what we're like!

Mrs Tortoise · Post by **Mrs Tortoise** » 3 Feb 2007, 7:27pm

Dai wrote:Presumably the measurements were done by one of us blokes - you know what we're like!

I see we're back to size again! :roll:

Terry T · Post by **Terry T** » 3 Feb 2007, 10:36pm

Try measuring the widths quoted, they're way off as well :roll:

reohn2 · Post by **reohn2** » 4 Feb 2007, 12:06am

Mrs Tortoise wrote:
Dai wrote:Presumably the measurements were done by one of us blokes - you know what we're like!

I see we're back to size again!

Yep yer right MrsT you can always tell when the men are posting :wink:

Jac · Post by **Jac** » 4 Feb 2007, 4:15pm

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. :roll:

David · Post by **David** » 4 Feb 2007, 4:25pm

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.

Terry T · Post by **Terry T** » 4 Feb 2007, 4:30pm

Oh I see, it's OK for the ladies on here to make sexist remarks is it :?:

Jac · Post by **Jac** » 4 Feb 2007, 4:36pm

Sorry - I did not mean to start another war :wink:

I expect it was a non gender specific illogical person who devised such a complicated system for measuring wheels. :lol:

Terry T · Post by **Terry T** » 4 Feb 2007, 4:42pm

That's better

reohn2 · Post by **reohn2** » 4 Feb 2007, 6:25pm

wheely Jac I don't what we're going to do with you!:0)

stevew · Post by **stevew** » 5 Feb 2007, 9:18am

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.

Charlie · Post by **Charlie** » 5 Feb 2007, 11:00am

I'm surprised nobody's yet asked the ever popular question......

Why are they called "clipless pedals" when you clip in and out of them?