The bicycle has been described as the parent of the automobile and grandparent of the airplane. Indeed, most of the technology found in early--and, in some cases, current--cars and planes was created for bicycle. The most famous, and possibly important, example is the pneumatic tire: Automobiles would be no faster or better than horse-drawn carriages, and modern aircraft couldn't take off or land, without them. Ball bearings and variable gears are among the other innovations that "crossed over" from two wheels to four.
Moreover, many of the early designers, engineers, manufacturers and even mechanics for automobiles of aircraft got their start with bicycles. Henry Ford and the Wright Brothers are among the most famous examples. Speaking of whom: Mr. Ford didn't "invent" the assembly lines for automobile production. It had already been in use in bicycle factories, and he adapted that innovation for the automobile company that bears his name.
As the cars overtook bicycles as the primary means of land transportation, "borrowing" shifted the other way. But as the bicycle industry in the US saved itself by selling its wares as toys or, at best, transportation for kids who weren't old enough to drive, the car-to-bike migration wasn't as technological as it was stylistic: Bike makers chromed parts for a "streamlined" look and added stick shifters and steering wheel-like handlebars to make their machines adaptable to childrens' fantasies of driving cars and motorcycles. (The "muscle bikes" of the 1960s--on the eve of the North American Bike Boom--are examples of what I mean.)
The cycle of innovation and borrowing continued when mountain bikes were first created. Many used brake levers and other parts from motorcycles and early suspension systems could trace their development--from springs and cables to air and elastomers, and back--to what was found on Harleys, Hondas and BMWs. And, whatever you think of them (I'm still not using them), disc brakes have been standard equipment on all but the smallest and lightest cars for about 50 years and are becoming more common on bicycles.
Now, it seems that the trend may be coming "full circle." A crew in Stray's Garage, an Italian custom motorcycle shop, created this "cafe racer" from a Soviet-era Ural motorcycle. Its most striking element, apart from its engine, is the front-fork suspension which, according to Cristian Curmei, blends elements of mountain bike rear suspension systems.
Oh, and the suspension system's piggyback oil reserve (near the top of the spring) bears a name familiar to mountain bike riders: Manitou.