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Old 07-27-2013, 08:46 AM
scr4 scr4 is online now
Join Date: Aug 1999
Location: Alabama
Posts: 15,013
I've read a lot about this topic as I've been riding recumbent bikes for a long time. (Many recumbent bikes have small wheels, some as small as 16", but some have 700c wheels. This is a topic of endless debate on recumbent bike forums.)

On a perfectly flat and smooth road, the wheel size makes negligible difference. Rolling resistance is mainly a function of tire construction and tire pressure. (However, if the tire construction and pressure are exactly the same, a larger wheel has less rolling resistance.)

On anything other than a perfectly flat pavement, wheel size has a bigger effect: larger wheels have less resistance. A large wheel effectively smoothes out the irregularities in the road. If there's a dip in the road, a smaller wheel sinks deeper into it, which means it takes more energy to climb out of it. If there is a bump, a smaller wheel climbs it at a steeper angle.

Also, you know the early bicycles with huge front wheels? The pneumatic (air-filled) tire hadn't been invented at that time, so a very large wheel was the only way to get a reasonably comfortable ride on solid rubber tires. The conventional ("ordinary") bicycle became popular after John Dunlop invented the pneumatic tire. (Yes, the large wheel also helped achieve a high speed without need of gears and chains, but gears and chains had been invented much earlier. Geared bicycles were invented, but did not become popular until it was combined with pneumatic tires.)

Last edited by scr4; 07-27-2013 at 08:49 AM.