This is a useful -- if gratuitously contentious -- thread. In particular, the advice about rolling slowly to cool off brakes, is very helpful. I poked around a bit since my first post here, and on the eMTB forums, there was a very similar debate, and those folks aren't stupid, either.
The consensus definitely favored intermittent braking, but with an important caveat for those of us who ride dirt: Sometimes, this is simply not possible. Descending Brand Park Motorway, and intermediate/advanced trail that has many patches of fine, loose, sierra sand, and VERY short stretches of up to 27%, I did notice that the steepest segments were not the problem-- I instinctively dumped speed before I hit them. What was treacherous was the gentler, 10%ish sandy stretches that are somewhat rutted and have modest amounts of rocks that
preceded the steep segments, or that happened before other problematic terrain-- sharp or blind curves, deeply rutted trails, or rock gardens.
Instinctively, I gritted my teeth and used continuous braking in these situations, and it seems like there is some broader agreement on this. Your brakes will lock up much sooner on sandy terrain, you have to avoid anything like hard braking or you'll lose traction. The sand builds up under your wheels or something, only very light braking is possible, and intermittent braking won't take off enough speed. (If you're going from a sandy section into an easy section with good traction, it may not be a problem -- you can brake intermittently and let the bike float a bit, that's part of the fun. Same thing if the sandy section is predictable, doesn't have ruts or rocks.)
@Stefan Mikes , I wouldn't say that riding the brakes is
wrong. I would agree that it is best avoided when possible.
I use both brakes on fast decents to slow down at my comfort speed.
On dirt or gravel road I only use rear brakes
Riding the brake is not advisable
Front vs. rear is a separate issue, but I do use the front brake even on sandy trails. I start by braking lightly with the front, to burn off some speed, then squeeze a bit harder for the rear. There's almost no danger of going over the bars with light front braking-- but descending a trail, I'd rather lose traction with my rear wheel than my front! If the front tire loses traction, I may not be able to turn properly. Gravel is easier-- only one gravel track that I ride, it's a circular route, and I only ride it going up!