Originally Posted by gastro
It would appear that the OP (as well as the majority of riders on this forum) use mechanical discs. Why would they get hydraulic fluid on their brake pads?
The contamination often comes for chain lubing. In my classic example, the kid at the bike shop lubes my chain by spraying Finish Line onto the cassette while pedalling backwards. The overspray hits the rotor and contaminates the system the first time the brakes are applied.
The second example is using any "dry" lube which ironically goes on EXTRA wet. The liquid lube splatters as you pedal backwards and gets on the rotor.
Actually, I think I need to cut a "rotor shield" out of cardboard for lubing. I had previously bought a Pedro's Chain Keeper, then I switched to a Karate Monkey which requires you to break the chain in order to remove the rear wheel at all. It kinda defeats the whole point of the tool ;-)