I've had this problem for some time now, both of my disc brakes on my MTB barely work, when i pull the front lever for example i can still push the bike very slowly. They have been properly setup like the tension in the wire and all and the pads seem to have plenty left on them. I have tried cleaning the pads and discs with rubbing alcohol and the problem still remains. Any ideas on what i could do would be appreciated.
Update So I decided to try and buy new pads and after going up and down a local hill a few times and bedding the breaks in, in a few minutes I managed to be able to do an endo. Still unsure why the other pads behaved as they did as before I installed the new ones I compared the new and old ones and the old ones had pretty much the same amount of compound left on them.