JAC wrote:Using Sheldons calculator, 700 wheels with 20mm tyres , 48/18 = 5.6m, and 49/16 = 5.7m, so these combos don't work for your son.
To confirm the actual rollout you are achieving with a wheel/tyre/gear combination, roll the bike along in a straight line and measure the distance covered for a full rotation of the pedals.
Have looked at Sheldons' calculator and keyed in the numbers so many times and kept getting 5.4 for 48/18, 700 x 20, 165 mm crank length. i might be using the wrong calculator.
Had previously looked at the Cycling Australia chart and yes 45/18 is perfect. 5.6 is the closet rollout that can be achieved with the current chainrings and sprockets. Unfortunately it looks like we can't get 5.5 with only changing a sprocket also. Will have to get a 45 chainring by the look of it.
Good advice to actually roll the bike when you have it set up. Thanks.