It is not easy to ask what size a tyre is when you are talking about a
cycle. A 20" tyre could be as much as 4" different from another one! There
is a system that allows being more accurate when specifying tyres and
needing to know what rim they fit on. The system is laid out by
The European Tyre and Rim Technical Organisation and it gives the size for
the bead and it’s diameter. I have done some hunting on the net and found a
good resourse for all these sizes:
Here is a text verson of some of them:
SIZE BIKE NAME/TYPE ETRTO
16x1.75 BikeE, Common Juvenile Tire size 305mm
16x1 Primo Race Tire 349mm
16x1 3/8 Vision, Lightning, etc 349mm
16x1 3/8 Also called “400a” Euro Bents, Roulandt 340mm
17x1 1/4 Moulton, Lightning, WindCheetah 369mm
20x1.5 - 1.75 Ryan, Haluzak, etc, Common BMX size 406mm
20x1 Primo Race Tire 451mm
20x1 1/8 - 1 3/8 Tour Easy, V-Rex 451mm
24x1.75 Seen on a Trek 820, anything else? 507mm
24x1 - 1 1/8 King Cycle, V-Rex, Terry front 520mm
24x1 3/8 “600a” Juvenile lightweights 540mm
26x1 1 1/4 Also called “650b”, Triathlon bikes 571mm
no, the 571mm size is “650c”.
26x1 1/2 “650b”, Euro utility bikes, tandems 584mm
26x1 3/8 “650a”. 3-speeds, cheap 10-speeds 590mm
26x1 - 2.125 Common MTB size, Vision, Haluzak, etc 559mm
700c x 18 - 38mm Common Road size, Tour Easy, V-Rex 622mm
27x 1 - 1 1/4 Common Older Road Bike size 630mm
Roger
The UK’s Unicycle Source