I am having similar issues with my 32. I had the wheels blasted and painted 20+ years ago but some of the tubes look as you described. I think if there is any roughness condensation/water will get in the pockets and rust develops causing the issue due to the flexing of the tire. As they fail I have been blasting the rough area and filling so the surface is smooth.  I am hoping that will solve the issue and prevent future problems.

Are you using rim strips? https://cokertire.com/instantsearchplus/result?q=rim+strips

I have taken wheels apart that have had duct tape in place of strips, not sure how well that worked.

Dave

Use tube flaps. You can get them at Tractor Supply, Amazon and others.

@david-dunton The rim strips only fit over the center of the rim to provide protection where the spokes are. My issues are where the very outer edge of the tire bead is in contact with the rim. I do have the rim strips.

@tiny do not see my size on tractor supply site. Have you got some from there do you have a part number. Thanks

I'm not sure what sizes they carry or what size you need. I've heard of folks, but never done it myself, making flaps themselves out of old tubes. Wherever you get them, my point was to use flaps to protect your tubes.