A lot of my riding is in country lanes as well as motorway
In good weather my rear brake pads lasts a long time (relatively) but when the weather is wet and roads dirty [and flooded] I can get through a set of rear pads in about 300 miles.
The rear caliper is checked regularly and the pistons and caliper cleaned. both pistons are happy to be pressed in by finger pressure and nearly match each other when pumping out. the holes in the disc get cleaned out often as well. I am now in possession of an overhaul kit and the spring plate that locates at top of caliper should I need to rebuild
I have checked that I am not dragging the brake with my foot, I have also bled out some fluid in case that was causing binding.
Now could it be that I have a hugger fitted and its directing a lot of the dirty water onto the disc; it certainly helps with keeping the silencer cleaner???
Goodness Brian, surely the discs must be getting red hot if you are consuming a set of pads in 300 miles! There must be something seriously wrong. There was a thread on the “1400 California” section that might be worth reading although the problem discussed, and eventually solved was not as severe as yours.
Cheers
In my work, we run test vehicles on an off road proving ground sometimes, which has very sandy soil.
On normal roads we can get about 1000-1500 hours from brake pads. On the test site we get about 50 hours, and if not checked daily they’re down to the back plate and then it’s new discs as well!
So I think your dirt theory may have some credence.
Ian