Most cars are unibody construction and the trailer hitches for cars generally don't mount on to any type of "frame". The risk of damage is not the hitch, but rather the sheet metal to which the hitch is mounted. Many cars have tongue weight limit 100lbs nowadays. Even if 150 lbs for the rack and two electric bicycles do not exceed the GVWR of the vehicle, it may exceed the tongue weight rating of the vehicle.