why 700c tyres were called 28"?

[Mick F]

When I ordered my Mercian Vincitore in summer 1986, I had the choice of 27" or 700c clearances.
Thank goodness I went for the (modern) 700c.

[Bmblbzzz]

My first ever brand new bike, in 1985, came with 27" wheels, but less than five years later it made sense to replace them with 700s.

When I started riding in 1976 most bikes had 27x1 1/4 wheels. When I moved to racing wheels they weren't referred to as a size - after all you went to the shop and just bought your tubs which were mostly a nominal 23mm. It was only later when viable lightweight tyre appeared on the market that 700c became common parlance to distinguish from the 27's.
28“ was however the typical size on many imported bikes, particularly town bikes. It wasn't until the late 80's that 27 wheels were replaced by 700 on lower priced 'road' bikes.

Yebbut which sort of 28" wheels? 622 or 635? And who called them 28" - the manufacturers or the UK retailers?

[NATURAL ANKLING]

Hi,
Not really sure whether we are getting any closer -
http://www.users.globalnet.co.uk/~pattl ... /tyres.htm

"Potted History

Before World War Two all tyres were measured in the same way, whether they were for lorries, cars, motor cycles, pedal cycles or wheelbarrows. This size was expressed as two numbers: the first being the overall diameter of the tread and the second being the height of the tread above the wheel rim; eg: 28×1½. If, for some reason, you wanted to know the rim diameter you just doubled the second figure and subtracted it from the first; eg: a 28×1½ tyre fits a rim 28 - (2 × 1½) = 25 inches in diameter. Of course, this meant that a 28×1¾ tyre could not be put onto a 28×1½ rim but, since no one was daft enough to try it, this didn’t really matter. This system was simple and easy to understand; therefore it had to be changed."

[Bmblbzzz]

Well that system might have worked when the ratio between tyre height and width was fixed. As soon as you start making tyres of different widths in the same "size", it breaks down.

[Brucey]

the 622mm rim originated in the UK (over 100 years ago) as the rim for 28 x 1-3/4" size, which has a rolling diameter of 28". The French used this rim size for what they called '700C' (not '700c') and in much of Europe tyres to fit these rims/tyres retained a 28" marking of some kind (anything rather than rely entirely on a French marking scheme...?... ).

So to this day in much of Europe they are called 28" wheels even if the tyres are narrower and didn't make the wheel 28" in diameter. In the UK if you ask for 'a 28" tyre' in a traditional bike shop you are most likely to be given a 28 x 1-1/2" tyre to fit a 635mm rim, which is the only 28" size that is still commonly found (there were lots, including some that fit 642mm rims).

The original 28 x 1-3/4" size lost popularity in the UK but 622mm rims did become popular again, having become the most common rim size in European sporting bikes, and almost universal in professional road-racing.

The 27" rim size was a late-comer; do check but IIRC it didn't really exist (and certainly wasn't popular if it did) until after WWII.

cheers

[RobC]

Thanks Brucey! That's a very useful explanation and was just what I was looking for. Now I can rest easy haha.

[NATURAL ANKLING]

Hi,
VHS & Betamax....................even Video 2000.
I remember the 27" coming home from school one day and rubbing on back wheel, the tube had popped out but still inflated, can't of been much air in it IIRC I just forced it back in
Every time I walk into Halfords for a gander we have another new sized wheel
I always though from what I had read that we started with 28" somehow.

P.S. was the 622 rim just a direct conversion of and English imperial size at that time

[tod28]

28"-2 x (1 3/4") = 24 1/2". 24.5" x 25.4 = 622.3 mm

[Brucey]

I found this chart in my travels, dated 1911;



the upper table shows the overall rim diameters for 'wire-on' tyres. Subtracting 9/16" from the rim sizes gives the bead seat diameter in each instance. All six sizes listed are still known today.

By contrast the 'beaded edge' tyres and rims in the lower table are extinct.

cheers

[NATURAL ANKLING]

Hi,
Even by todays standards that chart makes no sense as in imagine the confusement when you buy a tyre

"Clincher" Am I right in saying it started as a name of tyre not referring to type of tyre, I saw something the other day that suggested that?
As today the type is called hook bead rim?

[pete75]

The 27" rim size was a late-comer; do check but IIRC it didn't really exist (and certainly wasn't popular if it did) until after WWII.

cheers

Yep. I think the favourite with British club/sporting riders before the war and into the fifties was the 26 x 1 1/4 size - 597 in metric. I've an early fifties BSA "Clubman" type bike which runs these. The tyres are still available. The BSA has all British components apart from the Michelin tyres and even they were made here.

[Brucey]

Hi,
Even by todays standards that chart makes no sense as in imagine the confusement when you buy a tyre

Not really; the slightest examination of the rim profile would tell you what type of tyre you need, and then it is a case of choosing between six (very different) sizes, each of which fits only to one rim.

"Clincher" Am I right in saying it started as a name of tyre not referring to type of tyre, I saw something the other day that suggested that?
As today the type is called hook bead rim?

I don't know of its exact origins but I have carefully avoided referring to 'clinchers' because the name means entirely different things to different people.

Modern hook bead rims do provide some 'clincher' effect for sure, but neither the tyres or the rims are what vintage motorcyclists, motorists or cyclists might understand by 'clinchers'.

cheers

[NATURAL ANKLING]

Hi,
http://www.oldbike.eu/museum/tyres/pneu ... ghtbox/17/

"The advertisement above (adapted for my Online Sunbeam Bicycle Museum) is interesting in that it combines two products, Sunbeam bicycles and Clincher Tyres. Both were launched in America in the 1890s, a boom time for both bicycle and tyre manufacturers. This was also the beginning of the advertising industry as we now know it. In America and France in particular, full colour posters used dynamic messages and pictures of women to launch products …with such success that they transcended mere adverts to become a new artistic genre. Adverts in Great Britain (below) were somewhat staid by comparison"

[Brucey]

that is interesting but they were (fundamentally) not a very good idea; they could come off the rim entirely (without warning) if the pressure dropped below a certain point. The danger point wasn't always obvious (varies with load, speed, and exact quality of tyre fit) and was often at a pressure that was still too high for any real comfort to be obtained. Some folk routinely glue such tyres to the rim, and/or use MX style tyre clamps, because they are so troublesome otherwise.

These tyres were involved in numerous accidents back in the day and owners of vintage machines (cars and motorcycles mainly) with them fitted are still at risk today. One vintage motorcyclist has been killed in an accident which was caused by such a blowout quite recently. IIRC he'd been running his (new) tyres at 45 psi. He'd apparently been running 60psi (which would have been 'safer') but found the ride quality 'unbearable'.

It is probably difficult now to understand just how unreliable tyres were back then; the roads were less often nicely paved too (a state we seem to be reverting to.... ) which can't have helped but basically the tyres were not very good. Very many motorists would routinely carry more than one spare wheel/tyre, and if planning a long journey (say 1000 miles) it would certainly be necessary to carry at least one full set of tyres because they would wear out in that time, even if they didn't split for no good reason or blow off the rim in the meantime.

In the end the buying public voted with their feet and the wired-edge tyre became the norm.

cheers

[mercalia]

but 26" is just 26"? with my Marathon 1.75" tyres is more than 26" quite tall? must be atleast 27"