In a final attempt to get immediate strong rear braking, I swapped out my '14 FX's 25mm-piston J Juan rear brake caliper with the 30mm J Juan unit from the '15-'17 FX's. After packing the pin tubes with quality hi-temp grease (J Juan used a tiny amount of clear stuff and the pins started binding immediately) the brake is now almost perfectly consistent, and stopping power is quite good in the dirt using only moderate pedal pressure.
Pads: first I tried the
Brembo 07BB02TT carbon/ceramic units, which had decent bite & power, VG consistency, and quick break-in. After a while I wanted more power & bite, so I tried
Brembo 07BB02SX sintered pads: these had very good bite & power & excellent consistency, with a longer break-in. Neither pads squealed at all.
On the '14 FX, a different RH rear wheel spacer is needed to accomodate the thinner 30mm caliper mount, which is designed to work with the ABS wheel sensor on later models (diagram below, 'OAL' = .872"):
Caliper on bike - note standoff just visible at R edge of pic to keep brake line straight & above front of swingarm:
Ray