As other posters stated, primary tractor task is mowing. Unloaded tires work best for this application, again wet spring is a detriment. Also use tractor for snow removal. Was using the FEL float feature and that defeats the advantage of front wheel assist. When holding the snow pusher an inch or so above plowing surface, non-loaded tires perform adequately. The winter mounted back blade is only 400 lbs., not enough weight for true ballast.
Fact is, adding a heavy implement should provide all the needed ballast w/o loading tires. The wide R-4 tires used by compact manufactures isn't the best tractive solution. A narrower tire section width would actually provide better results but not look as cool!!