I came across this informative article about LT tires:
https://www.autosphere.ca/tirenews/tires-news/2015/10/20/lt-question/
some excerpts:
Quote:
Tire companies have responded with expanded product lines to fit this newish breed of vehicles that straddle the car-truck boundary, and continue to design and sell them in three classifications — Euro-metric, P-metric, and LT.
Dan Wysocki, who looks after tire fitment and validation for Fiat Chrysler Automobiles (FCA), says one way of simplifying the light truck tire landscape is to simply refer to both the Euro-metric and the P-metric tires as “passenger car” tires. “They are basically the same tire, a passenger car type tire,” says Wysocki
Euro-metric, which is also known as Hard-metric, was originally fitted exclusively to European imports, but now that the auto industry is globalized, P-metric and Euro-metric have come to coexist peacefully here in North America.
But as tire professionals know, the difference is quite vast, when you compare a passenger car tire and an LT (Light Tuck) tire. The LT tire features more robust construction, enabling it to survive in off-road conditions, and to shoulder heavier loads.
Higher pressures are ultimately what allow the LT to shoulder the heavier loads. Wysocki notes that LT tires designated with C, D, and E load ranges, run pressures of 50, 65 and 85 psi respectively, while passengers cars are typically inflated up to 35 psi.
“The LT tire is an entirely different animal,” says Wysocki.
….LT tires present all sorts of compatibility issues. “We design and engineer the vehicle for that size tire, and we recommend that you replace it with the OE tires,” says Wysocki. “The tire (pressure and load) information located on your tire placard, correlates only to the tire that is equipped on that vehicle. It doesn’t correlate to an LT tire that you might want to put on there.”
In addition to issues with tire pressures and whether they physically fit or not, the heavier LT tire may adversely affect the handling and durability of the vehicle’s steering and suspension components, which were optimized for the lighter passenger car tire. Wysocki notes that they would also not be compatible with the vehicle’s electronic stability control, and tire monitoring systems, which are set for the lower pressures.
...For slightly older vehicles without all the sensors, and with vehicles that are originally and/or subsequently beefed up enough to handle the heavier LT tire, the LT might indeed be the right upgrade.
...FCA’s Dan Wysocki also cautions pickup and SUV owners eying aftermarket 20-inch rims. Such wheels and tires will actually “decrease” their vehicle’s overall carrying capacity. “With the wheel getting bigger, the tire gets smaller, so you’re going to get less air into that tire. A smaller sidewall (and less air) will get you less load carrying capacity.”
