RedGL

New to the board and need some advice. I have am 89 GL10 wagon (bought new, only has 124,000 on it, just getting broken in). Anyway I had some tires put on about 15K ago. When I was having some work done on the rear axle, the mechanic noted that I was getting belt seperation on one of the tires. The warranty covered replacement but the tire is no longer made. Right now I have 185/70R13 on it. I can get a replacement all season in this size or the tire shop said the could replace the current tires with a set of 175/70R13. Now the manual says the 185 is rated for a "full" load while the 175 is rated for a "light" load. What's the difference between a full and light load?? Is having 3 passengers a full load while 1 is a light load?? Is it better to have the 185 size or would the 175 work? My son drives the car commuting to school and work. Thanks a bunch Joe