For what it's worth I put 155 passes on my 10.5W x 31 M/T w/o tubes or screws. At the end the 60's fell off about from 1.32-1.33 to 1.35-1.36 on average, but were still consistent. I don't run screws. The tires turned 180 degrees during the first 30 passes, then settled down.
Doug