by Administrator
21. September 2009 11:53
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About Light Truck and SUV Tires
Since these vehicles have so many different uses, it makes sense that several tire types are used on them as original equipment to complement specific models. These include:
Difference of Pickup & SUV Tires
Pickups and SUVs differ from standard Passenger Cars in their overall strength, load carrying capacity, center of gravity, and driveline complexity:
The main reasons many Pickups and SUVs are originally equipped with standard passenger tires is to lower rolling resistance and weight which enhances fuel economy and, of course, costs less.
* Most Pickups and SUVs feature a full frame and body construction to enhance their strength for hauling, towing and/or off-roading. While strength is important, it also adds weight which the tires must carry. Most standard Passenger Cars use uni-body construction.
* Pickup Trucks are available in different load carrying capacities. Compact Pickups often feature 1/4 ton (226Kg) capacity while full size Pickups feature 1/2 (453Kg), 3/4 (680Kg) and 1 ton (907Kg) capacities. When Pickups are in use they tend to be either lightly loaded or loaded to capacity. Also, because it is easier to "overload" a Pickup Truck than a passenger car, the tires are more likely to experience more stress.
* Pickups and especially SUVs tend to have a higher center of gravity than Passenger Cars. Ground clearance is very important for trucks that are to be driven off road and the only way to add clearance under the axles is to install taller tires. Designing the truck around taller tires, than would be typically used on a standard passenger vehicle, and providing sufficient clearance for the tires results in a tall vehicle package and a higher center of gravity (with more body roll and load transfer) which make the tires work harder, especially under braking and cornering situations.
* For the approximately 66% of SUV's and 29% of Pickups which feature 4-wheel drive, you have the extra weight due to the driveline's complexity. The additional weight of the front wheel drive axle and hubs, drive shaft and transfer case all add extra stress to the tires.
NOTE: O.E. manufacturers match tires to a truck load carrying capacity. What is the definition of a Light Truck Tire?
This is not as easy as it sounds. We define a light truck tire as any tire line or size which would typically be applied on a light truck vehicle (SUV, pickup, van). As such, it could be an LT-metric tire for use on a Ford F-350 or a P-metric 'light truck' size of a typical tire line such as the P235/75R15 on a Ford Explorer.
Types of Light Truck Tires
Since so many Pickups and SUVs are originally equipped with standard P-metric sized passenger tires it is important to understand the typical construction features that are added with P-Metric sized Light Truck tire designs and Light Truck designs in Light Truck sizes.
Click Here to view a chart explaining Light Truck Tire Types
| | Light Truck Numeric: | Prefix letters such as 'P' and 'LT' are used as part of tire size designations to differentiate between tires designed primarily for passenger and light truck service conditions. Definitions
(per Tire and Rim Association):
'P' Identifies a tire primarily intended for service on passenger cars
'LT' Identifies a tire primarily intended for service on light trucks
The load/inflation formulas developed for 'LT' designated sizes are different from those for 'P' designated sizes due to the more demanding load and service need on light trucks.
In order to properly select passenger tires for use on light truck vehicles (mini pick-ups, mini-vans, recreational vehicles, SUV's, full-sized 1/2 ton pick-ups and vans), the load capacity of the passenger tire at any inflation must be reduced by 9% and the maximum load capacity molded on the sidewall must also be reduced by 9%. | | 7.50R16LT | | 7.50 | Section Width in inches | | R | Radial construction | | 16 | Rim diameter in inches | | LT | Light Truck designation | | | | Light Truck High Flotation: | | 31X10.50R15LT | | 31 | Approx. Tire diameter in inches | | 10.50 | Approx. Section width in inches | | R | Radial construction | | 15 | Rim diameter in inches | | LT | Light Truck designation | | | | Light Truck Metric: | | LT235/75R15 | | LT | Light Truck designation | | 235 | Section width in millimeters | | 75 | Aspect ratio | | R | Radial construction | | 15 | Rim diameter in inches | | |
| | Ply Rating/Load Range
While there is no industry-wide definition of ply rating, truck tires are frequently marked with ply rating and equivalent Load Range. These markings are used to identify the load and inflation limits of that particular tire, when used in a specific type of service. The table shows the conversion of tire markings. www.tiresafety.com
| | PLY | LOAD | | PLY | LOAD | | RATING | RANGE | | RATING | RANGE | | 2 | A | | 14 | G | | 4 | B | | 16 | H | | 6 | C | | 18 | J | | 8 | D | | 20 | L | | 10 | E | | 22 | M | | 12 | F | | 24 | N | | | | |