The following article, A COMPLETE FAQ TO DISC BRAKES, was recently posted on CyclingTips.com and below The BRAKE Report is excerpts portions.
What are the advantages of disc brakes?
Similar to the brakes found in modern cars or motorbikes, disc brakes are widely thought to provide more consistent braking control versus a rim-based brake. Moving the braking surface away from the rim means that the rim no longer needs to serve the double duty of handling braking heat, retaining the tire, and resisting friction-based wear. And doing so allows the braking surface to be made from consistently surfaced steel or a similar effective heat-managing material, which in turn means the brake pads can be made from a harder and more durable material, too.
What are the disadvantages of disc brakes?
There are a few notable disadvantages to disc brakes.
Firstly, hydraulic disc brake technology is obviously more complicated and intricate than a mechanical rim brake system.
Disc brakes carry increased costs, something that’s especially applicable to road and gravel bikes where the hydraulic master cylinder must be integrated with the shifter.
Similarly, disc brake technology has more components to it and therefore, is more expensive. And at least on drop-bar bicycles, disc brakes typically introduce a small weight penalty, too.
There’s also the aerodynamic argument – I’ll return to this point.
Are disc brakes more or less aero than rim brakes?
All things being equal, disc brakes alone are marginally less aero than rim brakes. However, an increasing number of bike brands, such as Giant with their Propel Disc or Factor and their Ostro, claim that by removing the clutter of rim brakes and being able to open up room around the fork, the aero effects of a disc rotor can be more than balanced out.
If I imagine my rim as a disc rotor, surely I have disc brakes already, right?
In theory, yes, and also, no. Frame builder Rob English has jokingly argued this point nicely before.
Just to ruin a good joke, the advantages of disc brakes lie not in the size of the rotor, but in how efficiently force is transferred from the lever to the braking surface. The friction coefficients of carbon fibre and aluminium rims aren’t nearly as good as steel disc-brake rotors. Meanwhile, rim-brake calipers and housings are much more prone to power-robbing flex than compact hydraulic disc-brake calipers. Exceptions do exist, such as some specially treated rim-brake sidewalls and hydraulic rim-brake calipers, but for the most part, it’s really not the same thing.
There is much more information, as well as images, in the CyclingTips.com post and can be viewed by clicking HERE.