I have seen a number of ways to add fluid to tires on Utube, etc. Yesterday I decided to try it on my tractor (tire size is 23x8.5x12). I managed to get 5 gallon in each tire, weighed the tire and rim before and after, it increased the weight by 40 lbs. I put tubes in the tires and used -20 degree washer fluid.
I took the center out of a valve cap (white plastic punched out from threaded end) & clamped it in a piece of clear tubing on the other end I used a fountain pump. I also put a tee and a cap inline so I could burp the air out if needed. The ruler was to tell when it slowed down pumping.
Note, tee was not needed, when I unplugged power it would clear the air on it's own, I took the pump out of one of the wife's projects but Harbor Freight has some for less than $10.
It is a inexpensive rig and seemed to work well ( or at least better than I was expecting )
Good luck if you try it this way. Approx. 2 Hrs
Edited by grattone, January 18, 2017 - 04:16 PM.