After a ride, roll to a stop without using front brake. Check temperature of discs by touch. If one is significantly hotter than the other you need to exercise and clean the pistons URGENTLY or you will warp a disc. Undo caliper, put a piece of thin wood between pads, pump brake until pads grip the wood. Clean any crud off pistons and polish until shiny. Apply a smear of Red rubber grease to shiny surface. Push pistons back into caliper and refit. Repeat with other caliper. If discs still getting hot, you need to strip and service the calipers.