Originally Posted by jmyers
You may want to talk to a knowledgeable tire guy, but I believe the 1870 lb rating is at 50 lbs max air pressure. Running lower air pressure, especially on trailer tires, adds unnecessary stress on the tire sidewalls. It will also cause inside and outside wear at the same time, regardless of the alignment. You may be OK but for your safety and peace of mind please get an expert opinion. I'm running 225 75R 15 Load Range D Marathons (made in Canada) on my 30' Sandpiper (7,000 lbs dry) and I keep them aired up to the 65 lb max, and I never go faster than 60 mph, no matter what the speed limit. Maybe I'm overcautious but life's too short to spend my camping time on the side of the highway changing flats... or worse!
You are quite correct, the max load rating of this tire is 1870 lbs. Times 4 gives a total capacity of 7480 lbs. My TT weighs a maximum of 6500 lbs, with a tongue weight of 650 lbs leaving 5850 lbs on the trailer axles ,1990 lbs less than the tire capacity. If I reduce the tire pressure by 20% (10lbs), i will get a corresponding 20% (approx) reduction in carrying capacity to approx 6000lbs. This means the tires are well matched to the load, and therefore tire life,tread wear and safety are not jeopardized. Running these tires at 50 lbs would result in abnormal wear pattern and a very harsh ride. Unnecessary shock loads would be transmitted to the wheel bearings and trailer suspension.
Another example would be my TV ( 2008 F250) Tires are LT275R70/18 Load range E 3640 lbs.......times 4 = 14560 total tire capacity @ 80 lbs inflation.
GVWR on this truck is 10,000 lbs,or approx 70% of the tire capacity. Ford recommends no more than 65 lbs tire pressure, front and rear.Tire wear is normal at this pressure, although I don't usually run quite that heavy.
Many thanks to Jmyers@ rockwood06 for their replies/concerns. Bob