All single speed bikes, including fixed gear, have an absolute minimum of moving parts possible. Fixed gear bike, in fact, is the winner in this competition. It’s one chain, two sprockets, a pair of pedals and a handlebar. Of course, you still need two working brakes, but that’s a lot of money and energy savings on maintenance. All you need to worry about is to keep your chain well oiled and keep your eyes wide open. Fixed gear bikes are famous for their absolute minimums of maintenance needed. Most probably it is one of the main reasons they did become so popular with New York bike couriers in the 80s and 90s. A fixed gear bike is a simplicity itself on two wheels, but that’s only one side of the argument there.