Old 01-09-19, 06:02 AM
  #14  
PMK
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Join Date: May 2008
Location: Royal Palm Beach, Florida
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Bikes: 2006 Co-Motion Roadster (Flat Bars, Discs, Carbon Fork), Some 1/2 bikes and a couple of KTM's

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Originally Posted by mtseymour View Post



There is a fundamental difference between the Spyre and Hy/Rd due to "mechanical advantage" or leverage. Although the Hy/Rd is cable-actuated, it has a Master piston and two caliper pistons to close the brake pads. According to Pascal's Law, .pressure exerted on a piston produces an equal increase in pressure on another piston in a hydraulic system. If caliper pistons have an area 10 times that of the master cylinder (actuated by a brake lever), the braking force is multiplied 10 times. This is the basic principle behind heavy hydraulic lifts, car brakes, and truck brakes. This is why it's easy to get 1-finger braking with full hydraulic brakes. Attached is a diagram of the master and caliper piston in a hydraulic system.

Since Spyre lacks "mechanical advantage", it won't come close to a full hydraulic brake (eg. R785). The Hy/Rd comes second because it suffers from cable friction and smaller hydraulic capacity. The Sypre is a distant third, and is rarely found on new single bikes of good quality.
Fully understand hydraulics and the ability of hydraulics to multiply force.

The downside to multiply hydraulic force is the requirement of piston A vs Piston B linear travel. Multiplied you no longer have short stroke, but longer stroke.
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