My question about lead shot in tires was mostly in jest, but after reading the posts here I realized that if I were to do something like this it would be better to use large balls rather than shot because the lead would eventually grind itself into a really nasty slurry. This slurry would still work great but would be terrible to deal with come tire change.
I checked with the local scrap yard and 1/2 inch thick steel plate is 40 cents per pound. So what I'm gonna do is buy enough plate to make 4 ea. 2 foot diameter discs. The corners that get cut off of the rectangular plate to make discs I will weld to the discs, so no metal lost but for the kerf of the plasma cutter.
40 cents per pound seems like a pretty low price for weight. I think it's cheaper than beet juice. Since I already have about 200 pounds of lead I am also considering casting it into a frame that I can then bolt to the tractor using the same holes that the drawbar brackets use. There won't be a ground clearance problem for what I use the tractor for and the extra weight down low will help to lower the center of gravity.
My other tractors are a Ford 9N and a Case 580 CK backhoe. The Ford has calcium chloride and water in the tires, the Case just has air. The Ford has never seemed likely to tip over, but its rear wheels are set at the widest they can be. The Case does not have added weight, it really doesn't seem to need it. But it can get tippy feeling. Lowering the outriggers and swinging the hoe boom around really helps keep all 4 tires on the ground.
My little YM2310, though similar in size to the 9N, feels much more tippy. Even though, like the Ford, I have the rear wheels set for the widest stance, it still feels like it wants to tip over. The added weight will not only add much needed traction, it will also add stability. Especially the lead below the rear diff.
Since I retired recently I still have a complete machine shop along with torches, welders and a plasma cutter just 300 feet from my house. This makes fab jobs much easier. So adding the steel and lead should be cheaper for me than folks who don't have the resources and skills I am so fortunate to have.
Eric