Originally Posted by ultrachrome
I drag my brake to prevent lurching due to chain slack. Perhaps there are other reasons but controlling this slack that is inherent to the design of the bike makes it much easier to control when riding a bike just off idle.
I asked about using the rear brake to a driver instructor that I know.
This was the answer:
The easiest way to explain this is to think about towing a car.
The front car tows (the engine of your bike) and the other one can be seen as your rear wheel.
The rope that connects the cars can be compared with the chain and gears of your bike.
To tow the car without jerking, the rear car should have just a little more resistance (for example by using his brakes) to keep tension on the rope.
your bike has the same principles, by braking your rear wheel and have the engine towing, the gears and chain will remain with tension and you have less jerking and become more stable by doing so.
this is also usable at higher speeds, but it requires more practice.