20 by 1.75 and 20 by 1.5 - the rims are 406mm
1.5's are generally for 'expert' sizes
the funky thing here is..
mini and junior rims 20 by 1.1/8 and 3/4 are actually 451mm
yes they are bigger, hense some times you cant even fit a 20 by 1.5 into a mini/junior, as you cant get to the caliper 'more over new school canti's
plus a sew up is some where in the middle, they have never been given a metric 'etktro' whatever it is sizing - but they do fit minis
beacause 406mm is actually 16 inches
a sew up is 17 inches - a whole inch closer
-hense a 1.5 is for a if yoike 'normal sized bike, but with a smaller top tube 'expert' - 13 year old
where you arn't too heavy, and use a 1.5 tyre instead of a 2.1
its confusing old school to new school, as mini's and juniors i think differ a bit
