Tyre/wheel sizes

For discussions about bikes and equipment.
Brucey
Posts: 42911
Joined: 4 Jan 2012, 6:25pm

Re: Tyre/wheel sizes

Postby Brucey » 5 Nov 2019, 9:48am

Chris Jeggo wrote:Brucey has mentioned ISO bead seat diameters of 584 and 590 above. These sizes were common in the UK for many years, but under another name. 26" wheels were in the majority, and their overall diameter, including the tyre, was pretty close to that nominal 26". The two common sizes were 26 x 1-3/8" and 26 x 1-1/4", but a tyre so labelled would only fit on a rim identically labelled....


26 x 1-1/4" tyres fit onto 597mm rims.


The reason for 'overcomplicated' answers is because 'simple answers' are usually also wrong answers.

The OP almost got the idea that 28" = 700C = 622mm rims. This is essentially repeated above as if it were true.

It isn't.

It is both wrong, (there are several different -incompatible- 28" sizes in current use) and also fails by omission; you will also find tyres that fit 622mm (BSD Bead Seat Diameter) rims labelled as 29" tyres.

So armed with a 'simple answer' someone could either buy the wong tyre or assume that a given tyre isn't going to fit because it says it is a different size. 'Simple answers' like that are no use to anyone.

The CUK page on tyre sizes is similarly incomplete and needs updating.

cheers
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Darkman
Posts: 144
Joined: 30 Aug 2019, 8:46pm

Re: Tyre/wheel sizes

Postby Darkman » 5 Nov 2019, 11:40am

Must say, the answers prior to tim_b and the utility cyclist were, with the best of intentions, super-confusing.

Didn't realise tyre/wheel sizes were this much of a minefield.

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Chris Jeggo
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Joined: 3 Jul 2010, 9:44am
Location: Woking

Re: Tyre/wheel sizes

Postby Chris Jeggo » 5 Nov 2019, 11:47am

Brucey wrote:
Chris Jeggo wrote:Brucey has mentioned ISO bead seat diameters of 584 and 590 above. These sizes were common in the UK for many years, but under another name. 26" wheels were in the majority, and their overall diameter, including the tyre, was pretty close to that nominal 26". The two common sizes were 26 x 1-3/8" and 26 x 1-1/4", but a tyre so labelled would only fit on a rim identically labelled....


26 x 1-1/4" tyres fit onto 597mm rims.



You're absolutely right. Thanks for correcting me. I knew that, but had a temporary memory lapse when writing my last post.

And 26 x 1-3/8" tyres fit onto 590mm rims, a mere 7mm smaller.

The ISO numbers are the only reliable ones.

Brucey
Posts: 42911
Joined: 4 Jan 2012, 6:25pm

Re: Tyre/wheel sizes

Postby Brucey » 5 Nov 2019, 12:07pm

once in your hands, it is not difficult to say whether any given tyre will fit your rims or not; just look at the ISO size markings.

But tyres are not always described for sale using these markings , so if you want to have a simple statement that captures all the different ways such tyres might be described, with no omissions, caveats or exclusions, it is less simple than that.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

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The utility cyclist
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Joined: 22 Aug 2016, 12:28pm
Location: The first garden city

Re: Tyre/wheel sizes

Postby The utility cyclist » 5 Nov 2019, 3:57pm

Brucey wrote:once in your hands, it is not difficult to say whether any given tyre will fit your rims or not; just look at the ISO size markings.

But tyres are not always described for sale using these markings , so if you want to have a simple statement that captures all the different ways such tyres might be described, with no omissions, caveats or exclusions, it is less simple than that.

cheers

Yourself and others have added reams of superfluous information which confuses those that aren't in the know, just say what identifies the tyres sizing wise, that's three different versions, answer in basic terms the questions plus giving some direct pointers to suitable example tyres would have also made it easier for the OP, however none of you did that, hence they've taken up rowing and not being back! :roll:

Brucey
Posts: 42911
Joined: 4 Jan 2012, 6:25pm

Re: Tyre/wheel sizes

Postby Brucey » 5 Nov 2019, 9:18pm

'superfluous information' is IMHO infinitely preferable to misleading folks with the impression that all 28" tyres will fit 700C rims etc etc

Advice like that is not worth having; it both allows you to buy the wrong tyres and it omits to mention tyres that will fit.
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fastpedaller
Posts: 2777
Joined: 10 Jul 2014, 1:12pm
Location: Norfolk

Re: Tyre/wheel sizes

Postby fastpedaller » 5 Nov 2019, 9:52pm

The utility cyclist wrote:
Brucey wrote:once in your hands, it is not difficult to say whether any given tyre will fit your rims or not; just look at the ISO size markings.

But tyres are not always described for sale using these markings , so if you want to have a simple statement that captures all the different ways such tyres might be described, with no omissions, caveats or exclusions, it is less simple than that.

cheers

Yourself and others have added reams of superfluous information which confuses those that aren't in the know, just say what identifies the tyres sizing wise, that's three different versions, answer in basic terms the questions plus giving some direct pointers to suitable example tyres would have also made it easier for the OP, however none of you did that, hence they've taken up rowing and not being back! :roll:


People (many 'bike shops') also disregard the ISO measurement. All that is required (to ensure a tyre will be 'best fit') is to use the ISO sizes :D