The bigger tires have less compaction to them than walking on a lawn. Most of a persons weight is on the heal of the shoe, so you can have as much as 200 or more pounds of weight in a 3" X 3" area. Another thought, when your heal hits the ground,it is doing just that, hitting the ground, where a tire is rolling smoothly over the ground. A big tire has around 300 or 400 pounds over a much larger area, so they don't compact the ground as much as just walking on it. Aerating helps with this and many other things, so my nicer lawns all get spring and fall aerating.<p>----------<br><a href="http://www.townserver.com/elm/">Eric@ELM</a><br>