Sorry, but I have to throw a flag on the play here ...
Kevin -- That chart is for radials on single piece wheels, yes? Should we even be using it for bias plies with tubes on multi-piece wheels?? I think under inflating bias plies on multi-piece wheels could be dangerous ...
John -- Not to put too fine a point on it, but we *are* playing with the man's life here -- we need to be certain, not think or guess when discussing whether or not to disregard the pressure listing on the tire itself. The engineers back then weren't stupid -- they came up with those numbers for a reason. So IF there is a point we can safely underinflate to for a softer ride and still maintain the integrity of the wheel ... where is that point? And what are the consequences of getting that point wrong?
Yes, I too, would like to hear from someone with experience in this. For the moment, and for the record (and to save my butt in these litigious times ...), the official Stovebolt.com position is to maintain the tire at the pressures stated on the tire itself. As the pressure in the tire is what actually holds the wheel together, under inflating tires, especially older, less pliable ones, on multi-piece wheels is dangerous and should be avoided.
I think this is actually another instance in this hobby where you can't have your cake and eat it too -- In the original configuration (wheels, tires, suspension, etc), you can either have a softer ride *or* maintain your load carrying capability -- but not both. There are things you can do to soften your ride but I suspect they will either impact your load carrying ability or be expensive. As is, please do not under inflate your tires! The one time you load the truck and forget to properly inflate the tires ... blowouts do not always occur under optimal circumstances ... There you are, under a load ... at speed ... downhill ... on a curve .... with underinflated fossilized tires ... and your outside dual blows ... followed quickly by it's suddenly overburdened partner ... Do you have seatbelts installed? Ever thought about the solid steel rod pointed directly at your chest? (i.e., the steering column ...)... The ride you will then take will not be enjoyable. And quite possibly, not even survivable. We would prefer that not to occur.
To put it far more bluntly -- if you want a softer riding daily driver -- you have the wrong truck.
Sorry...
John
