I am considering filling the rears on my XR3037HC. After using the loader and forks a few times it seems the rear feels kind of light. I am thinking of using either washer antifreeze or RV antifreeze. My local TSC store has RV AF on sale for $3 a gallon. I figure I need about 35-38 gallons per tire so that figures to $210. or so plus tax, plus an air / water fill valve. I have a 10% coupon for TSC so the price would be $189.
70 plus gallons of washer fluid (the good stuff) is about the same price. Estimating each gallon weighs between 7-8 lb. I'd be adding 490 lb at 7 lb per or 560 lb at 8 lb per gallon. I already have the pump so the fluid, valve, and my time is the only expense to me.
Beet juice / rimguard is a little heavier by weight but would more than double the cost.
Calcium requires tubes and if you ever get a leak it will eat the metal rims.