Originally Posted by
mtseymour
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If you overheat 254mm rotors, it's likely that you're using BB7 or Bengal mechanical disk brakes with a single piston. These are obsolete designs without hydraulic brake's "mechanical advantage", dual pistons, and self-centering pads. Not surprisingly, you can't find mechanical disk brakes on good-quality single road or mtn bikes. If these brakes are not good enough for a single, why use them on a tandem? I also hope that you modulate your brake (squeeze and release) rather than use the rear disk as a drag brake to "save" the front caliper on steep descents.
This conflates different things. The ability of a disc brake to dissipate heat is dependent on the actuation only to the extent that the different designs, materials, parts, and construction may have different heat dissipation properties. So for example, hydro vs cable/mechanical may differ due to plastic parts on one melting or the brake fluid on the hydros boiling, which cant happen with cable actuated. Other than that, hydro vs cable/mechanical, dual vs single-piston, self-centering, etc, have no affect on the ability to dissipate heat. Nor does the mechanical advantage of the brakes have any affect on ability to dissipate heat. The advantage of hydros is that they require less force at the lever to generate the same force at the pad/rotor interface. Rotors- size and design, and brake pads- material and design, are what determines the ability to dissipate heat.