What happens when I mix P-metric tires with light-truck tires?

Question

I have P mertic 6-ply on front and 10-ply LT on rear

Answer 1

P-Metric tires are 4-ply, not 6.

If your truck was designed for an E-load LT-Metric tire by putting P-Metric's on you have seriously underloaded the tires and created a potentially dangerous situation with a high probability of catastrophic tire failure. It is NEVER recommended to install P-Metric tires on a vehicle that specifies LT-Metric tires. If your truck specifies LT-Metric's whatever shop installed the P-Metric's is not only completely unprofessional but has exposed themselves to considerable liability.

You don't say what size or what type of truck so let's take a common example instead. A P265/75R16 tire has a load index of 114. That means at 35 psi it has a maximum load capacity of 2,601 lbs when applied to a passenger car but this has to be reduced by a factor of 1.1 when applied to a light truck so its actually 2,365 lbs. Maximum inflation pressure of this tire may be only 35, 41 or 44 psi depending on brand and model.

An LT265/75R16 with a load index of 123/120 (E-load) has a load capacity of 3,415 lbs at 80 psi. Recommended inflation pressure, depending on the year/make/model of truck and front or rear axle will usually be between 50 and 80 psi - far in excess of what a P-Metric tire can safely be inflated to.

So, each P-Metric tire has a load capacity more than 1,000 lbs less than the LT-Metric tire and can not be inflated to anything close to the minimum inflation pressure required by the vehicle. Under-inflated and overloaded tires have a high risk of failure. That's what happened with all those Ford Explorers a decade ago. My advice would be to remove the P-Metric tires immediately and replace them with the proper sized tire if LT-Metric tires are specified for your truck.

What if it is the opposite and you have LT-Metric's on a truck that only requires P-Metrics?

In that case, leave the LT's on the rear axle and make sure you inflate to at least 50 psi. At 35 psi for example (a typical pressure recommendation for light trucks with P-Metric tires) the LT tire in the above example only carries a load of 1,910 lbs - significantly less than the P-Metric at the same pressure. LT's need more air. They squrim like crazy if under-inflated too. There is no specific RMA guideline about mixing P-Metric and LT-Metric tires on vehicles that only require P-Metric, but I still wouldn't do it. All four tires should be the same size and service rating, and preferably the same brand and model.

ASE Certified Automotive Service Advisor with 5 years experience in the tire industry

Answer 2

10 Ply Light Truck Tires

Answer 3

I owned in basic terms one %.-up truck, and it became right into a small stay sparkling of Ram. (The D-50 sort.) Passenger motor vehicle tires are actually not rated for the a lot a %.-up is able to wearing, and function better sidewalls for use on tough terrain. After talking with some friends (One owns a Ford F-250, the different a Chevy Silverado.) they pronounced they might use passenger tires given that the truck became into in no way used as a artwork truck or taken off highway. (yet the two admitted that they had in no way tried it.) I used popular tires on my D-50, however the truck became into in no way used as a truck. The occasional piece of furnishings each and every now and then for a pal, yet in no way an entire load. (Which became into not very lots besides on the stay sparkling of.) And the closest I got here to off-highway became into the gravel motor vehicle parking zone on the capturing variety. i might say that in case you know you will not "load it up", tow something, or stress on tough roads that the passenger tires could artwork superb. i might seek for suggestion from with the tire save supervisor as to what the guarantee on the tires may be in case you used them on the truck. If the guarantee is void, it might extremely be a larger wager to adhere with the truck tires.

Answer 4

You'll mess up the handling characteristics of the vehicle as well as risk blowing a tire due to an overload.

P-type tires are for passenger cars. Unless the manufacturer recommends P-metric tires you should not use them as they do not have the correct load carrying characteristics that your truck needs. And you should NEVER mix P-type and LT-type tires on the same vehicle.

Answer 5

Normally the "LT" Light Truck tires have a higher load range than "P" Passenger tires. That means they could fail if over loaded. The LT tires also have a stiffer sidewall than "P"s,
"P"s may cause a squirmy feeling ride on the road.