Truth about dually tires rubbing each other

I've heard that dually tires touching is a really bad thing, and I understand how it could be... sorta

Anyway the long story is I got a freebie 78 P-series step van with 10-year-old 7.50x16 flat tires. I replaced them with some good used 235/85-16 and the rears are darn close to touching. Can they touch a little, not at all, how much space is safe?

You get really strange and odd tires failures from duallies touching - not 100% of the time, but more often than you would if they didn't touch.

Dual spacing is done centerline to centerline and for LT235/85R16's it's supposed to be 10 3/4 inches. BTW for a 7.50-16 the spacing is supposed to be 10", and since ost of the tie vehicle manufacturers used something close to the minimum, I'm guessing this is what you have.

But you have a problem that isn't easily solved. One solution would be to find 7.50R16's - yes the do exisit.

Another would be to use LT215/85R16's, which need 9.88 dual spacing, but thy are slightly lower in load carrying capacit, so you need to be careful.

Another would be to live with the problem knowing that you'll kind a close eye on the tires and remove the at the first sign of trouble.

Thanks for the in-depth tech. For now I think I'll keep an eye on it and also start looking for later wheels with the wider spacing.

Thanks