Originally Posted by WhatNoise???

Could be deposits on the rotors. Or if the pads aren't stock, perhaps the pads weren't bedded correctly…

If you decide to try the hard stops, bring the temperature of your rotors up gradually, so you don't shock your rotors with extremely hight temps (this could definitely warp them). Start by slowing down a few times applying medium pressure for 2-second intervals to bring your temps up and then do a few fairly hard applications at speed (2-second intervals). Don't come to a complete stop, if you can help it. This may make things worse by adding more deposited material because the rotors are hot. Do a couple of hard slow-downs and then just cruise to let your brakes cool down for a bit.