My 49 Chevy truck has a 3 piece split rim and I've changed tires and inflated them without a cage, but never stand over the rim while inflating and make sure the rim pieces have no rust in the grooves and everything seats together well. I assemble mine and put in a few pounds of air, then lightly tap the lock ring to make sure it's firmly seated, then inflate all the way. I can't tell from the picture exactly what style rim you have, but it might have some rust issues in the grooves.