Originally Posted by BlazingPedals

You probably have BB5s on your trike, since those seem to be the lowest-level brand name ones around. BB5 are pretty fiddly to set up since they lack an adjustment for the inner pad. I think you're stuck with shims to adjust the inner pads. Are you sure this isn't a problem with truing the rotor? Most mechanical disc brakes work by moving the outer pad and deflecting (bending) the rotor into the inner pad. This leads to warped rotors.