|Avid BB7 mechanical cable disc.|
At present, with most of the mechanical disc brakes out there now, you have control of the cable length and tension as well as the position of both the inboard and outboard brake pad. Through these individual adjustments you control how far away from the rotor the pads sit at rest. This is very different from hydraulic brakes, which are self centering in their pad position and distance from the rotor. They also self compensate for pad wear, a key aspect of the mechanical brake issues.
The only way to adjust for pad wear with a cable actuated disc brake is to readjust the pads. This unfortunately requires getting off the bike and screwing the inboard and outboard dials individually on an Avid BB7, a pain in the butt. You can, however, get half way to dynamic in-ride adjustment by installing an inline cable adjuster, which effectively lengthens the cable housing, shortening the slack on the cable. This has the effect of actuating the lever arm which sets the outboard pad inward, toward the rotor. The downside is that the inboard pad remains fixed still. The new TRP cable actuated mechanical calipers that are supposed to be out soon actuate both pads via a crossover arch and will solve this issue, making them manually adjustable on the fly. Of course, the TRP hybrid cable actuated hydraulic calipers will be really sweet when they show up.
|Avid BB7 SL rear.|
The last tip is one that I've discovered to be helpful over the years. What I do is to preload the actuator arm a little bit. This means that with the cable taught, there is some back tension on the cable from the arm wanting to return to full rest. I'm not sure if the arc that the actuator arm makes during the travel stroke is slightly non-linear (doesn't appear to be) but this seems to drastically improve the feel. Of course by preloading you start actuating the outboard pad but as long as it isn't rubbing, you are fine.
With this setup I have been able to race up to 1:08 in some very, very sloppy and gritty conditions (2012 Plymouth P/1/2/3 day 1) and 45 minutes in some insanely sloppy conditions while working the brakes over really, really hard on the steep downhills (2012 Downeast M45+ races), for the entire races on the same bike, without losing braking. I was also never required to adjust mid-race via the inline adjuster. I'm not sure why so many people were running out of brakes but I have to guess that it was due primarily to setup.
|Noticed the bulge last night. All done.|