Mechanical disc brakes

[Moodyman]

Is there a technique for applying mechanical disc brakes? (Shimano if it helps)

I find they're great when I need to make an emergency stop i.e. sharp braking and briefly. The bike stops instantly.

But, on long descents they start to lose power the longer I go into a descent. The harder I break, the less the breaking.

I know you're supposed to break in intervals, but is there a specific technique? e.g short sharp dabs?

I've checked all the usual stuff: lever only comes back a third of it's full distance, the pads are aligned correctly.

 

[GrasB]

Sounds like good old fashioned fading to me. Basically the disc &/or pad gets too hot & so applying more pressure only serves to decrease braking efficiency through increased thermal load. There are 3 ways around it:
1) Brake less on one brake. If you're using your front brake all the time try using the rear for general drag & the front to give you more power when needed
2) Fit bigger discs. These have more surface area to dissipate heat. You're using a larger swept area to brake so each bit does less work for the same braking performance. Apply more retardation for the same pad pressure so you don't need to brake as hard to start with so they are less prone to overheating
3) Use vented discs. Heaver but they are much more effective at dissipating heat so don't fade as much.

I believe option 3 is only really available in hydraulic applications, so you're left with 1 & 2.

So to answer your question, use the back brake to lower your coasting speed but use the front when you want to decelerate quickly. I've personally found that a 183mm front disc is much better than a 160mm though a lot of fork manufactures only rate for 160mm.

 

[GrumpyGregry]

I found when I first took up with discs my technique changed. With V's I'd feather the brakes and ride with them on just a bit for a long time. Then I blew a tube doing that and vowed not to make that mistake again...

...with discs I find I grab bigger handfuls less often and much later than I did with rims. The relative predictability of discs lets me get away with this (most of the time)

 

[GrasB]

I once rode down Mucklows Hill on a tandem with disc brakes. You could have fried bacon on them by the time we got to the bottom.

Oh yeah 4 options... get better pads that work over a wider temp range! Mintex M1155 or Pagid blue please