Why aren't hub/drum/roller brakes suitable for touring? I've got a Dutch town bike with Shimano IM80 roller brakes. They're brilliant. Maintenance free, clean, and effective. 

I've been looking at getting a long range touring bike for an initial 3 month camping/hostel trip to Japan, and so I need a more suitable bike. It's probably best that I stick with what I know and like, but it seems that everyone says roller brakes just won't do it.

Why is this? Here's a summary of the issues and my initial thoughts.


"They can't cope with sustained braking on descent."
Is this because of temperature? The cooling fins on a Shimano IM81 roller brake are huge compared to disc brakes. Why is this a problem?
"They can't handle heavy loads."
I give lifts to adult passengers on the back of my heavy bike (a total weight of at least 150kg) and while braking performance is affected it's not catastrophic.


I would really appreciate answers that address the technical performance and safety issues that mean hub brakes aren't recommended. I'm aware maintenance (particularly in the field), weight, interoperability, and style are other factors that need consideration independently from the operation. Thanks!
Their main problem is your first bullet hypothesis: They can't cope as well with sustained braking on descent, as that is where brakes are challenged the hardest. 

Even with the extra cooling fins, on a long descent, the brake may overheat, and may catastrophically fail. Riders using roller brakes have reported the brakes getting hot enough to ignite the internal lubricants inside the hub when making descents on tandems or loaded bikes. 

Even if you had cooling fins the size of the wheel, you are generating heat inside the hub, and that heat has to travel out to the fins, which is surprisingly slow. Going down a mountain, you theoretically could have your hub start on fire, while the outer parts of the cooling fins could be cool to the touch. Disc brakes don't have that as the source of the energy is at the caliper which is on the outside of the rotors, but even then those have failed from overheating too.

The weight aspect on its own isn't too big a deal, even with heavy loads,
you can only slow down so much before you are completely stopped. However, when descending, you can drag the brakes and build up heat faster than it can be dissipated, and combining a descent with a heavy load doubles the demands on the brakes.

Ultimately, every bicycle brake system turns kinetic energy into heat, and has a maximum wattage it can operate at continuously. What increases the wattage is greater deceleration or greater loads.

If you were touring across Iowa, you'd be totally fine. Japan is pretty mountainous. If you are going to only be traveling where the terrain is pretty gentle, you'd probably be OK. If you are going into the mountains though, you'll want a different brake system.