Well I got around to more tire dismounting/mounting. I had a Mil trailer with 9x 20 tires and I got a flat. I also still had several 11x20's sitting around that needed work.
I finally got a real duckbill hammer, but the handle was junk so I replaced with a nice hickory handle derived from a Mattock handle. The handle was longer than normal which works perfectly as I am 6'2 and almost all handles feel too short.
Anyway I got some soapy water for lube and proceeded to try beating the 11x20 tire down from the lock ring.. No go.. I was going to try my jack hammer but I found I was missing a bit..
For some strange reason I had a gallon of corn oil in the garage .. I think it was in some vehicle I bought?? Anyway, I decided to try corn oil for lube, so I poured probably 2-3 cups (yes .. that is a lot of oil) around the lock ring and then called it a night.
A couple of days passed and I pulled out the duck bill hammer ... this time the tire moved. It pounded down with effort but at least it moved. Once I got the duck bill under the lock ring I used a 5 lb sledge to drive the duck bill down further. (Much safer than swinging that big hammer) I pulled the lock ring and removed the tire and it was evident that the oil had soaked down through the corrosion as it was actually on the tube in a few places behind the flap!
Tire #2 - a 9x20 which had been on a trailer for a long time - probably 20+ years but the tire was still like new.
More corn oil.. let it sit overnight. The tire slid right down with probably a dozen swings.
I put the 9x20 back together after patching the tube. I used my pressure washer to wash out the tire, the rim and ring and flap.
Wire brushed the rim and ring after it dried and sprayed the steel parts with rustoleum and let that dry.
Reassembled the tube and flap and put a little corn oil on the rim and flap to facilitate assembly.
In just a few minutes I had the ring snapped back on and aired up the tire after mounting the wheel with the ring facing the frame.
I'm sold on corn/veggie oil. I have uses Pam kitchen spray for years on rubber so the corn oil just made sense.
The nice thing about corn oil is that is is non destructive to rubber yet it is very slippery and apparently it penetrates very well also.