Despite the fact that the majority of a bicycle's stopping power comes from the front brake, many novice and casual riders worry that if they apply that brake too hard, they'll go flying over the handlebars. As a result, to be on the safe side, they often only use the rear brake. It was for cyclists such as these that the Slidepad system was created. It allows both brakes to be applied with the squeeze of a single lever, in such a way that the front brake will never lock up on its own.
Here's how the system works ...
The rider squeezes the one and only handlebar-mounted brake lever, which has a traditional-style cable and housing running to the rear brake (Slidepad only works with rim brakes, not discs). As the brake pads engage the forward-turning rim, one of them actually slides forward a bit with it – the brake calipers and the other pad remain in place.
A second cable, attached to the back of that sliding pad, loops forward and proceeds up to the front brake. As the pad moves, it pulls on the cable, thus activating the front brake a split-second after the rear one. The process is illustrated in the video below.
Various manufacturers already offer an alternative – single brake levers that can accommodate both front and rear brake cables at the same time. Why not just use one of those? "Two cables hooked up to one lever means there is always a fixed amount of braking to each front and rear brake, it doesn't change if you're on a slippery surface, leaning too far forward, etc." explains company president Brian Riley. "Slidepad's breakthrough innovation is that it allows the front brake force to intelligently change based on the riding situation ... For example, if the rear wheel begins to lift off the ground as if you grabbed too much front brake, the front brake is instantly released, which will likely prevent an unwanted accident."
Slidepad was developed primarily for bicycle manufacturers to build into their new models, and is already standard equipment on several of Jamis' latest bikes. It will also be featured on soon-to-be-released models from Sun and Torker. It can additionally be purchased as a kit for retrofitting existing bikes, which is priced at US$49.95.
Source: Slidepad
If it jams up in those conditions then it is not fit for general use.
http://www.google.com/patents/US4102439
The Calderazzo design cites the earlier Peckham patent which achieves the same thing.
http://www.google.com/patents/US3882971
David Gordon Wilson wrote in his book, Bicycling Science, that prototype testing for the Calderazzo system eventually caused fatigue failure of the fork. Given that much stronger forks are easier to design today, that shouldn't be an insurmountable problem. Patent disputes did kill the system back then, though.