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Sanding a contaminated rotor does fuck all
Tim has spoken! I’d like to know why it works so well for the 100 or so times I’ve done it? When combined with some sort of cleaning fluid. If I drop the sandpapering I get worse results.
MCamb-
I’d like to know why it works so well for the 100 or so times I’ve done it? When combined with some sort of cleaning fluid.
Because you've cleaned it.
Sanding takes off the embedded pad material from the rotor (which is microns thick, not enough to hold a contaminant) so it's useful when switching to another pad compound, but there's no reason to do it when cleaning. All it does is mean you have to repeat the bedding in process again, and wears your rotors and pads out quicker.
TooTallTim
You don't need to sand rotors unless you're switching pad compound. Sanding a contaminated rotor does fuck all apart from move the contamination around. Assuming it's mineral oil, clean rotors with IPA. If they're resin pads, bin them and put fresh ones on. Sintered you might get away with burning off the oil in the oven, but at today's energy prices, new pads are cheaper.
Assuming DOT, wash the rotors in hot soapy water. See above with pads.
Then bed the pads in properly, drag them til they're warm then 10 or so firm brakes but don't come to a standstill.