free parking spot to get to münich airport (Munich)

hi,

i am living in allgäu and fly quite often from munich airport. although i usually get the train to get there, from time to time i need to drive myself. if my trip is over a week or so, i pay quite something for the parking at the airport..

i would like to know, if anyone knows parking possibilities which are safe and free of charge with an easy connection (s-bahn, bus, etc.) to the airport..

answers would be appreciated..

cheers,

umut..