So as a 100kg+ rider on a disc brake road bike I made myself, who enjoys travelling fast down a steep descent, I reckon I can
weigh in on the topic. I've also had a decade or two in motorcycle racing and had the first disc braked MTB in the national series in Australia, so I've got some history.
Disc brakes work. We know why and how. The patents on the successful designs are set in stone and if you want to make disc brakes for bikes then you have to pay the designer/patent owner to license it. Option
B is to try and work out some
other way that engineers gave up trying to get around since Freddy Lanchester patented them in the late 19th century.
There are couple of absolutes in disc brake design. The first is that the rotors are
critical to brake performance. They're not an afterthought that can be machined away until they simply resemble a rotor's silhouette. As everyone pointed out, heat is the enemy of performance. The very purpose of a friction brake is to convert kinetic energy into heat energy...
period. The heat energy then needs to be transferred into the atmosphere before it overheats the hydraulic fluid, boils it and creates compressible bubbles of gas. The greater mass of the friction surfaces and everything connected to them and the greater its ability to conduct the heat, the better. This includes the rotor.
The second thing is sufficient surface area to dissipate the heat. The best component to catch and dissipate heat is the rotor. The design, again, is well developed and the best rotors have small cross drilled holes. The most fashionable have elaborate machining that a). Doesn't absorb much heat from the friction material yet climbs quickly to very high temperatures and b). Warps under moderate heat load causing the pads to have even less contact area and subsequently less stopping power.
High performance automotive brakes generate tremendous amounts of heat. As an example, my sports car has cross drilled, ventilated, floating CAST IRON brake rotors to absorb and dissipate the massive heat generated from those big red brake callipers. Now obviously we're not going to use cast iron rotors on a bicycle, but I think it illustrates a point about how heat-dissipating rotor design takes precedence over light weight, even to famous sports car manufacturers where cost is not an issue.
The other issue for my mind is the large number of fluid connections in the TRP hydraulic system (and many others). All these connection points present multiple areas for air to enter and remain in the system during both set up and under high heat loads where dissimilar metals expand at different rates/heat loads. Even a small bubble trapped in a banjo bolt connection can present a problem in a small volume system under stress.
In my view, this guy lost his brakes because he used those silly aftermarket rotors that failed to dissipate any heat which then caused his caliper to overheat the fluid which in turn stressed the system into introducing and/or releasing trapped gas into the fluid. The user's rotor choice error was exacerbated by having a typical opposed piston caliper with poor heat dissipating features. TRP supplied rotors that they've tested and work very well but, this
clever gentleman knew better than the engineers that put the system together... and as often happens, made quite a hole in the scenery, then blamed TRP and disc brakes in general.
Thousands of guys use a setup like this on massive descents like those at Les Gets and you see the noobs holding the brakes on the whole way down a half hour descent on a 55lb bike over bumpy terrain without ever getting fade. Other, poorer designed brake systems fade at the first hint heat build up because of the haphazard mix-n-match ebay sourced components that work together only because the bolt holes line up.
My bike has cross drilled stainless steel rotors (small holes
not big missing pieces). Cooling fins on the caliper. Airflow over the pads by using a sliding caliper design without opposing pistons. Lightweight ceramic pistons (under those cooling fins). A closed 'factory charged in a vacuum' hydraulic system with no hose connections and minimal exposure to the atmostphere, even under high heat loads. The caliper, including the master cylinder and sliding caliper carrier and brake mount weighs 169g each end and the 160mm rotor weighs 115g and the rear 140mm rotor weighs 95g. The result is a very powerful brake system that stops my fat ass without any problems at any speed at anytime so far. I use the same system on my MTB, my commuter and the road bike and I have never been less than amazed at Horst Leitner's brake system. The only problem is that you can't get them any more unless AMP-Research either start making them again or license the patent to someone who will.
Anyhoo, the moral of the story is:
Use the rotor specced for the system. That is
not the place to save weight. Just ask Brembo.
After hoping for the last couple of days that the TRP PArabox would arrive in my letterbox, I check the Royal mail Trace page only to get this message 
It's here !!! 
