Ok, let me try here. Your car has a certain amount of mechanical steering limited by the steering blocks hitting the c hub. Your servo should provide more movement than is nessisary to have the steering block contact the c block, so when that occurs and your servo continues to power its self you are creating tweak, and could even damage the servo's internal gears. You dial back the EPA so that the servo no longer forces the steering block into the c hub but just stops shy of contacting it.
It could be a worse case senario here that you are jumping teeth in the servo explaining why your steering doesn't return to straight on.
Last edited by AlBundy; 01-29-2017 at 07:12 AM.