The cable doubler increases the probability of a cable failure, and only insures that you will skid your rear wheel under maximum braking. Get rid of it and use a standard front brake, with a second lever in a different but reachable position for a rear brake. You can use the rear brake on downhills to prevent front brake overheating, and you will have a redundant system. The front brake will stop you just as fast as two brakes, and without skidding the rear wheel.
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Last edited by eddy m; 07-08-19 at 06:50 PM.