Ok, so how exactly do I fit a 11 inch wide at the setting bead tire onto a 12 inch rim? Tire shop refuses to do them, says they are too narrow. Diameter is same, 10 inch, but rim is 12 inch at sealing area and tire is 11?
Same way as you fit a new tyre that is squashed to a funny shape.
put the tyre on the rim , support the tyre clear of the ground, lube the top bead and push down hard on the rim to get one bead in place.
remove the valve core so you can use a duster gun to inflate the tyre
Flip the tyre over and wabble the rim up & down to try and get the second bead to touch while applying air through the valve body.
method 2
Start as per above but put a strap around the tread.
Tighten the strap to force the side walls out then inflate as per above.
Remove strap & if the beads stay put replace valve core & inflate as normal.
Method 3
Put a tube in the tyre and inflate till the beads are seperated by well more than 12 "".
Leave in the sun for couple of days.
Sometimes the tyre will then mount as normal
Method 4
Explosion.
Start as per method 1
put some flamiable liquid in the tyre, open end up,
With a flame on the end of a long stick, hold it near the open bead till the fluid ignites
Watch ewe tube videos on this method a few times to see how it is done
Remember fire safety, chance of stuff flying everywhere ( eye protection ) and being burned , thus the long stick.
I have used all methods, they all work, some will work better with some tyres than others.