LT Tire Knowledge

Joined
Jan 31, 2006
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Idaho
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.”
 
Joined
Oct 9, 2004
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11,295
Location
Cincinnati, OH, USA
Transits have OEM labeled Class "C" LT tires that can handle 85 PSI (LT235/R16C Hankooks)-can't really automatically assume pressure settings on LT tires, which should be adjusted to match the axle load carried.
 
Joined
Jan 14, 2013
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Wisconsin
Originally Posted By: bullwinkle
Transits have OEM labeled Class "C" LT tires that can handle 85 PSI (LT235/R16C Hankooks)-can't really automatically assume pressure settings on LT tires, which should be adjusted to match the axle load carried.
You're right they are c's. we have had a lot issues with the OEM Hankooks on our Transits. A lot of flats, bad in snow, and wear fast. They are being replaced with E rated Firestone Transforce HT's. Sorry going off topic. Just wanted to mention they're terrible.
 
Joined
Feb 22, 2003
Messages
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Somewhere in the US
Originally Posted By: bullwinkle
Transits have OEM labeled Class "C" LT tires ......
Allow me to explain what is going on here. It's a bit complex and convoluted and I hope I can do this clearly enough to be understandable. In the US, the tire standardizing organization is "The Tire and Rim Association" - TRA, for short. That organization uses the letters *LT* in front of the size for tires designed for a certain type of application, which they loosely call Light Trucks. These are 3/4 and 1 ton pickups and vans - BUT - the designation covers quite a wide range of sizes that don't really fit that mental image. Note that TRA uses load ranges. In Europe, the tire standardizing organization is the "European Tyre and Rim Technical Organization" - ETRTO. Over there they use the letter "C" AFTER the size. There are some very slight differences, especially concerning the difference between English units and Metric units. Over the years, those 2 organizations have tried to minimize those differences, with limited success. Note that ETRTO used Ply Rating in place of Load Range. However, a 6PR = LR C, 8PR = LR D, 10 PR = LR E, etc. -- AND -- It is not uncommon for tire dealers to mix the 2 systems when describing a tire. Tire Rack seems to be doing that. FURTHER, because of the difference between the 2 systems, you may see some odd max pressures. You may also see tires with both the letters LT and C. The quote above refers to a Ford Transit - which was at least partially designed in Europe for European consumption (primarily), but has been brought over to the US for commonality reasons - and what came along for the ride is the European "C" designation - at least partially.
 
Joined
Jan 2, 2004
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California
Originally Posted By: CapriRacer
However, a 6PR = LR C, 8PR = LR D, 10 PR = LR E, etc. -- AND -- It is not uncommon for tire dealers to mix the 2 systems when describing a tire. Tire Rack seems to be doing that. FURTHER, because of the difference between the 2 systems, you may see some odd max pressures. You may also see tires with both the letters LT and C.
I've been seeing those when I was helping a friend get tires for his VW van - it called for a 185R14C tire, a hard to find size in the US. A lot of the replacements were LT185R14C and BFG did make a LT195/75R14C version of the All-Terrain T/As. GM did put a label on the GMT400 platform trucks and SUVs that said use LT245/75-16 or LT265/75-16 tires for enhanced load carrying and trailering abilities. However, those trucks do have a crude ABS system.
 
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