i have searched the forums and found alot of people describing thier tires that they run on thier cars. now to describe my situation is my speedo is off about a steady +15mph. when i leave from a stop it almost instantly jumps to 20 mph. so my question is im running 205/40/17's and would that be enough to through it off that much. or does this sound like more a vss problem. also the car appears to have been converted from a/t to m/t. im trying to fix all the problems with that before i swap my tires for more reasonably sized tires like a 45 or 50 series. any suggestions would be appreciated.