And today I picked up a contaminat on the rotor while ridong around. I'll be busting out the brake cleaner tonight when I get home.
Can you spray that stuff (brake cleaner in a can from an auto shop) on the pads? No worries if not, I am familiar with the dishwashing technique and the BBQ flambe method.
Take the wheels off, spray the rotors and clean them. Take the pads out then either blow torch them or give them a spray/clean with brake cleaner... then use some fine(ish) sandpaper on a flat surface and scuff off the surface of the pads.
Give the calipers a good clean with brake cleaner when the pads are out.
Shimano 4 piston brakes ? I have found are very susceptible to contamination... cant put my finger on why but I have had issues with every set I own with occasional pad/disc contamination... which I have never had with any other set of brakes, ever. Also cant find any brake fluid residue coming from anywhere obvious on the caliper but originally though it may be spraying from the piston area onto the disc on hard braking.
Own 4 sets BTW, 3 x XT and 1 x Deore.