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D
D Lock
A type of lock in the shape of a “D” which is considered to be very strong.
Derailleur
Simple device that pushes the chain sideways from one gear cog to the next. A rear derailleur is slightly more complicated as also has to compensate for the slack in the chain caused by changing gears.
Domestique
A rider on a cycling team whose main role is to support the team leader and keep him out of trouble.
Drafting
Cycling close behind another rider in order to take advantage of the fact they are making a hole in the air.
Drivetrain
The parts of a bicycle which have to do with generating forward motion. These include the pedals, cranks, bottom bracket, chain, derailers, rear sprockets and rear hub.
Drop Handlebar
A drop handlebar is most often found on road bikes built for speed or long-distance riding. They provide a range of different grip positions, allowing the rider to change positions for comfort and to adapt to different road conditions and gradients, and to create an aerodynamic position.
Dura Ace
Shimano’s top of the range componentry.