Wheel ruts, which form as a result of repeated passes of the towers over wet ground, can be a problem. Unless the site is very sandy, and you are sure that wheel ruts will not cause problems, machines should be fitted with “dry-wheel packs” (half-throw sprinklers on solid drops or boombacks at each tower), to minimise the amount of water hitting the towers and wetting the wheel tracks.
Minor additional capital expense on a dry-wheel pack (say $1500 to $4000) can prevent significant repair jobs later. More than $25,000 has been spent on several sites to repair severe ruts - see DPI Agnote “Centre Pivot Wheel Rutting”.
Bad Wheel Rutting
Hopper and crowder developed to drop gravel in wheel ruts
Wheel track filled with gravel