<font color="blue"> Looking at used tractors which have foam in the tires. These were rental tractors and the foam is used to prevent flats. I was planning on filling the tires, Ag's, with water for better stability. Im just not sure if the foam filled tire is an advantage over water filled. </font>
Hi,
Foam around here is on the dense side apparently, and weighs more than water they tell me [and I believe it after feeling the weight of my front tires after foam filling].
The difference between foam and water as far as the affect on the overall center of gravity is probably a moot point. With water the center of gravity of the tire will be slightly lower than the axle, due to the air space, but the foam filled tire will be a little heavier...probably equals out in the end.
Rat's point about traction is interesting. The foam filled tires will probably not deform much...but you could run lower pressure in a water/liquid filled tire and increase the contact patch improving traction. The foam tire will probably just be a "what you have is what you get" situation. No option to run different pressures...
Personally I would not worry too much about the tires being foam filled. I know my rear R4s at 12 psi do not seem to flex out much if any even with my backhoe on [Kubota B2910].
I filled my fronts because of punctures from glass in one area I was cleaning up. Seems like the people who lived here years ago use that place as their dump, back before trash pick up was common.
If punctures on the rear were common I would be back at the shop getting my rear tires foam filled too.
Personally, if I were buying a used tractor and it had foam filled tires I would consider that a positive...as long as the tractor was in good condition. Hopefully the need for foam tires on the tractor is not also an indicator of abuse by the former users...