Cycling UK Forum

Is there any particular reason why we ended up with 622s and 560s? Why was there a decision to phase out 26(fractional) sizes, 27" and 650b? There must have been a reason
a - before they became standard for race/mtb
b - why they became the standard

Standardisation. Every country had its own standards/sizes so they were standardised under the ETRTO system. See here

Tyres and rims used to be made by the same manufacturers, so there was an incentive to have different size rims to lock the buyer into your make of tyre. Later on, rims started being made by different companies so tyre makers had to make their tyres to fit available rims. The less popular sizes dropped by the wayside, with less choice of tyre and fewer companies making them, as a result of which fewer new bikes used them and fewer people bought them. I wonder how many more Guv'nors Pashley would have sold if they hadn't made the somewhat perverse choice of a 635mm (28") rim?
In general terms, somewhere in the 26" to 28" size range is best for a bike - too small and the wheels don't roll so well, especially on rougher roads, too big and the bikes don't fit smaller people. (559 MTB with road tyres can be down to 24", but roads now are better than they used to be.)

Tubular tyres have always just been a single size, and 622 (700c) became a popular rim for race style bikes because you didn't have to adjust your brakes when putting the race wheels on. 630 (27") was always a UK only size, pretty much, and dropped out with the decline of British manufacture and increasing imports.
559 came about because 26" x 2" was the size of rim for the fat tyres available in the US when the initial MTB boom started. If MTB had initially developed in France, I dare say MTBs would all be on 650B instead.

ETRTO sizing was an effort to make sense of the confusion caused by fractional inch sizing. Even the tyre manufacturers were getting confused and labelling tyres incorrectly in some cases, let alone customers buying the wrong size for their bike.

I've read somewhere, probably in the CTC mag, an explanation by CJ which went into the history of this. I can't remember anything about mountain bike wheels, which is all wrapped up in the history of American bikes*, but I think the 27" versus 700C thing is that the industry more or less settled on 700C and the Brish bike trade, for protectionist reasons went its own way with 27" which was near enough to work the same but meant the British market for tyres and rims was unique. (Remember British meant half the world "sun never sets" etc.) This was similar to Raleigh having its own thread sizes etc. Around the same time that the manufacturing part of the British cycle industry went belly up, the importing part of the British cycle trade decided what would be what.

* There is something on SB about American bikes - I think he uses the expession "clunkers."

andrew_s wrote:I wonder how many more Guv'nors Pashley would have sold if they hadn't made the somewhat perverse choice of a 635mm (28") rim?

dunno, but don't knock 28" or 29" till you've tried it. the comfort over bridlepaths, cobbles and the like has to be tried to be believed.

andrew_s wrote:Tubular tyres have always just been a single size,

Not correct, they came in 27" size before 700C

andrew_s wrote:Tyres and rims used to be made by the same manufacturers, so there was an incentive to have different size rims to lock the buyer into your make of tyre. Later on, rims started being made by different companies so tyre makers had to make their tyres to fit available rims. The less popular sizes dropped by the wayside, with less choice of tyre and fewer companies making them, as a result of which fewer new bikes used them and fewer people bought them.

So our current sizes are mostly based on market forces "back in the day" which dictated the "popular" sizes and therefore the ones that continued to be made?

Tonyf33 wrote: Not correct, they came in 27" size before 700C

Are you sure? I'd have put my money on andrew_s being correct.

THERE IS ACTUALLY NO SUCH THING AS A "27 INCH" TUBULAR.

That's what SB has to say on the subject and the capitals are his, although I agree it's written in the present tense.

I think a lot of the sizes that were prevalent over here i.e 27/630, 26/597, 26/590 were down to Dunlop making slightly different sizes to corner the UK market. I wonder whether this happened in other countries (650B/584 being prevalent in France and it's colonies).

Chaps, may I draw your attention to The Dagworth & District Gentlemen's Cycling Society's guide to tyre sizes. There's a little bit of history thrown in for good measure, which helps to explain a little of how come we are where we are with tyres.

http://www.users.globalnet.co.uk/~pattle/ddgcs/tyres.htm

I hope it helps throw a little light on the topic, or at the very least lessen the shadows

A further drift away from the original system occurred in the 1960s with the introduction of the well-known 27×1¼ tyre. (Note: there was a 27×1¼ pre-war but it had become obsolete when this later version was introduced. If you have a cycle with this pre-war 27×1¼ size wheels, the bad news is that the post-war tyres won't fit... but the very good news is that 700C tyres will.)

I cannot speak about the rest of it but that bit - which is central to this thread - is simply wrong. By that I mean that there is nothing in the bit I have quoted which is correct.

PS To reinforce the point this is not IMO, IMHO, IIRC or anything else which might provide me with an escape route if somebody comes along with something different. There has only ever been a single 27 x 1¼ size of tyre and it will not fit 700C.

I picked up on that too.
700c fits 27"?????

thirdcrank wrote:PS To reinforce the point this is not IMO, IMHO, IIRC or anything else which might provide me with an escape route if somebody comes along with something different. There has only ever been a single 27 x 1¼ size of tyre and it will not fit 700C.

He seems to be suggesting there was a 27 x 1¼ pre-war which was different to the much later 27 x 1¼. I don't think he's suggesting the 1960s-onwards 27 x 1¼ is the same as a 700C.

He may be wrong, he may not be; I wasn't around pre-war, but these chaps have some very unusual and ancient iron in their bike sheds, so I can't rule out anything.

I can only tell you that for wired-on tyres as opposed to tubs, when I started cycling in the late 1950's with some pretty ancient stuff, there were only two common sizes 27 x 1¼ on 'lightweight' bikes and 26 x 1⅜ for utility bikes. Although my memory does not go back pre-war, I know that during the war when tubs were difficult to source, people raced on very lightweight 27 x 1¼ wired-ons the "25"s were really light and the "50"s a bit heavier.

I suspect that the author of your piece is getting mixed up with tubs, which were always 700C, and wired-ons. As I mentioned above SB has an explanation about how similar confusion occurred in the US. In my lingo, wired-on = clinchers in his.

http://www.sheldonbrown.com/gloss_tp-z.html#tubular

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Edit to add I've found this in Classic Lightweights:

http://www.classiclightweights.co.uk/de ... onloy.html This is the relevant bit:

Sometime during 1935 Constrictor introduced a new version of the hollow rim which was just a little narrower and a little lighter. This was the classic Asp rim ...Now all Constrictor crescent shaped rims are often known as Asps but the name was reserved for the narrower section rims. At about the same time Dunlop introduced a new wheel size, the 27 x 1¼in (630mm bead seat diameter) which was not related to any other size. Constrictor soon offered the Asp in Dunlop’s new size as well as the two common 26s and what Constrictor called continental 27s – what we know as 700C.

thirdcrank wrote:I can only tell you that for wired-on tyres as opposed to tubs, when I started cycling in the late 1950's with some pretty ancient stuff, there were only two common sizes 27 x 1¼ on 'lightweight' bikes and 26 x 1⅜ for utility bikes. Although my memory does not go back pre-war, I know that during the war when tubs were difficult to source, people raced on very lightweight 27 x 1¼ wired-ons the "25"s were really light and the "50"s a bit heavier.

I suspect that the author of your piece is getting mixed up with tubs, which were always 700C, and wired-ons. As I mentioned above SB has an explanation about how similar confusion occurred in the US. In my lingo, wired-on = clinchers in his.

http://www.sheldonbrown.com/gloss_tp-z.html#tubular

Lots of good info I've never used tubs, so hadn't even considered them. Sounds very likely it has confused the author of that article