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Low-Profile
From WikiPedalia
- Low Profile Cantilever Brakes
Traditional cantilever brakes have arms that stick out fairly far to the side. These protruding arms sometimes get in the way of pannier bags, and the rear brakes sometimes interfere with the rider's heels on smaller frames. As mountain bikes became popular in the 1980s, the heel clearance issue became a serious problem, because mountain bikes generally used smaller frames than traditional designs, placing the seatstays lower. The riders' heels; banging into the ends of the brake cantilevers became a real concern.
The industry responded with a re-designed cantilever whose arms were angled up higher, and didn't stick out so far to the side. This fixed the heel clearance problem, but introduced problems of its own.
With low profile cantilevers, the mechanical advantage decreases as the brake shoe moves inward toward the rim, an undesirable characteristic which causes the braking performance to deteriorate sharply as the pads wear down.
See also my article on Cantilever Geometry. - Low-Profile Cranks
Traditional cranks run roughly parallel to the bicycle's centerline from the bottom bracket to the pedal. Most newer cranks use the "low-profile" design: the bottom bracket is made shorter, and the crank runs outward at an angle from bottom bracket to pedal, giving improved heel clearance for riders who tend to pedal splay-footed.
Note: That a crank is "low-profile" says nothing about its tread width (a.k.a. "Q factor.") In fact most "low profile" cranks have fairly wide tread, but this has nothing to do with the "low-profile" design.
The trend toward wider tread resulted from the wider chainstays introduced with mountain bikes, and also the additional clearance required to keep the right crank from rubbing against the cage of the front derailer (newer front derailers optimized for triple chainwheels require more crank clearance than older front derailers did.)
