Hi Bob, what air pressure are you running in the tire then? I've always been told that with car tires, you run the recommended tire pressure from the owners manual, which is usually less than the tire max. On the other hand, I've been told with RV tires, which I'm not sure would include trailers, you run the max listed on the tire. Would be interesting to see any charts that provide a scale of pressure vs. weight. I came across this recently also with what pressure to run in my car tires with the additional tongue weight of the trailer. I got an interesting reply:
Subject: RE: FW: Tire info
From: Colin Przybyla The Tire Rack <colin@rerack.com>
Date: 7/16/2013 9:14 AM
To: "mcs2442@gmail.com" <mcs2442@gmail.com>
Hello
We don’t have a specific recommended inflation for the 2010 Toyota Highlander when towing. The
recommended inflation when towing should be obtained by Toyota, since they do validation testing with
a loaded trailer to determine the max towing capacity. You may need to contact Toyota directly if the
information is not in his owner’s manual, since the dealer will likely not know the recommended
inflation pressures when towing.
Your OE tire sizes are P-metric and achieve max load at 35 psi, so increasing inflation will not increase
load, but may provide less sway as the vehicle travels down the road. If you are using a standard load
Euro-Metric tire, the max load is achieved at 36 psi and Euro-Metric XL the max load is achieved at 41
psi, so increasing inflation above those levels will not increase the load capacity of the tires, but may
provide less sway as the vehicle travels down the road.
Best regards,
Colin Przybyla | Sales Specialist
I've always ran the tire sidewall shown max pressure in my trailer tires. Considering the side loads placed on tandems (or more) while turning, I'm not sure running them with any less is beneficial and may actually be disadvantageous. You do bring up a good point about wheel (rim) max pressures also. Anyone increasing to a higher load range tire, should insure the rest of the equipment can handle the load as well. My load range C tires, using 50psi, show a max weight rating of 1,760 lbs. On a tandem that's 3520 per side or 7040 for the boat and trailer. My C-22 and trailer weigh 5065 total, with 4660 of that on the axles. In my mind I have plenty of reserve weight capacity on my load range C tires when everything is working properly. With a blown tire I'm going to slow down and just limp along to a safe place to put the spare on.

For tires that should be replaced every 4-5 years, I'm not sure I see the need to upgrade to a more expensive tire. Colby :smiled