From ERS: "We know when replacing an ST tire that has a particular max load rating on the sidewall with an LT tire that has a load rating listed on the sidewall that is higher that is an OK situation. That one is a no brainer. The problem is when the load rating on the LT sidewall is a little less. It may actually be if you could recalculate the load of the LT using the K factor for the ST, it might actually be a step up and be OK. The problem is we don't have a chart for this."
I am planning an upgrade from ST's to LT's and am in this exact situation. The sidewall rating of the LT (Michelin XPS Ribs) is 3042 lbs. This is a LOT less than the 3420 lbs on the original Towmax ST's, but it still meets/exceeds the 6,000 lb axle rating. I asked CapriRacer the specific question of whether I would be better off going to Maxxis ST235x80R16's or Michelin XPS LT245x75R16's (nearly identical diameter of the originals) right before the last thread was shut down. He pm'd me and indicated the Michelin LT is the more robust tire and is the preferred choice. I think I understand that the difference in load rating is eclipsed by the different calculations for the two tire types.
p.s. Francesca, I like your question.
