Originally Posted by
Andrew R Stewart
Many riders don't know how to shift a front der well. So they complain about how poor their bike's gears are. Bike companies hear this and see a market. Riders are greatfull they don't have to shift/drop the chain in front any more and they can also be "with the times". Also bikes with rear suspension have challenges with frt ders and suspension elements playing nice location wise. Andy
It doesn’t help that the front derailer is a poorly designed mechanism for what is supposed to do. Torque and tension on the chain are higher when moving towards lower gears. For the almost all rear derailers, except for Shimano’s Rapid Fail, the cable is used to move the derailer and chain while under this kind of torque and tension. In other words, the derailer is
pulled onto the gear under load so it has to shift. Very seldom will a rear derailer balk at a downshift.
Compare that to the front derailer where the spring has to push the chain off onto the lower gears. If the spring isn’t strong enough, the cage will just rub up against the chain until the chain drops when the rider reduces torque on the pedals. Often it won’t drop at all. Years ago, Suntour made a front derailer for mountain bikes that was high normal like Shimano’s Rapid Fail. The cable drug the chain off the chain wheel which made shifts more like a high normal rear derailer does. It was a much better mechanism.
Rapid Rise was supposed to make shifting easier since the levers moved in the same direction for front and rear from low to high. If they would have made a high normal front derailer, we’d probably still have triples and front derailers.