Quote:
Originally Posted by motto
Some makers back then actually gave the tyre outside diameter as part of its identity i.e. 7x34 although that wasn't general practise and fell by the wayside.
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I don't have a source to quote but am quite sure the 7x34 size designation was for a separate series of tires, sometimes referred to as "high pressure" tires. I think the "high pressure" was in comparison to "balloon" tires that were supposed to be lower pressure and thus give a more comfortable ride. For the "high pressure" tires the 7 referred to section width (and approximately height) and 34 was the overall diameter which would go back to a 20 inch rim.
Until they started putting belts on tires (either bias or radial) all tires were close to 100% aspect ratio as there was little to stop the tire from taking on the shape that would give maximum volume for minimum circumference - cylindrical. once the use of belts started, the belt limited the diameter of the tire which in turn permitted the tire to be wider than it is tall. Think of the long skinny balloons clowns manipulate into other objects for the amusement of the crowd. (animals, hats, swords etc.) (Actually, a sphere has more volume per surface area - but is awkward to use as a tire.)
Here I am, finally getting some use from the calculus courses I failed so often at university.