W, 200 W inputs, gave results as follows: Efficiency testing of bicycle gearing systems is complicated by a number of factors - in particular, all systems tend to be better at higher power rates. 200 W will drive a typical bicycle at 20 mph, while athletes can achieve 400 W, at which point efficiencies 'approaching 98%' are claimed. At a more typical 150 W, hub-gears tend to be around 2% less efficient than a derailleur system assuming both systems are well maintained. See also Cogset Comparison of hub gears Cycling Electronic gear-shifting system Gear inches Cycling terminology Mountain biking Outline of cycling Sprocket Sturmey-Archer References Bicycle gears ja:変速機 (自転車)