By Matthew Barnes
Having the right tire on your pickup can improve performance and be one of the best safety strategies you can employ; having the wrong tire on a pickup truck can ruin a good day. Not to overstate it, but tires are one of the most important components on your vehicle, and knowing a few basics will ease the tire selection process. Choosing the right tire can be a daunting task as there are so many options and pieces of information to keep in mind.
While this discussion mostly covers radial tires, there are many topics and issues that carry over for the few people looking to purchase bias-ply tires. Of course, getting into the habit of regularly checking your tires is always a good idea. Worn, improperly inflated or damaged tires can be dangerous to you and others.
All tires are marked with the width, sidewall height ratio or overall height, rim size and load range. An example of what you might see on the sidewall is LT315/70R17 121/118O. Here's what that means:
- Tire type, LT, shows up first in this example but it can be placed in other spots as well
- 315 is the tire width in millimeters
- 70 is the ratio of sidewall height to width: 315 x 70 percent = 220.5-mm-tall sidewall
- R indicates radial
- 17 is the rim size in inches
- 121 is the load rating, but the load is also listed elsewhere on the tire in pounds
- 118 is the load rating if the tire is used for a dually setup
- O is the speed rating listed as a letter, not a number
- On the left of the photo above there is a three-peak mountain with a snowflake and an M+S, which indicate that this tire is good for mud and snow and ice
Another way to label a tire is in inches; for example, 35X12.50R20LT.
- 35 is the tire height in inches
- 12.50 is the tire width in inches
- R indicates radial
- 20 is the rim size in inches
- LT is the tire type
- M+S indicates that this tire is OK in mud and snow[JB4]
- At the bottom right of the photo above is load range E, which is another load rating for the tire
- At the bottom left of the photo above are the weight ratings: 1,450 kilograms or 3,197 pounds at 65 psi cold
The tire has a few other markings placed on it such as the date stamp, Department of Transportation number, which direction the tire should be mounted if it's a directional tire, whether it's a tubed or tubeless tire, and safety warnings.
Tires get several load ratings; here's what those letters on the tires mean:
P stands for passenger in a P-metric tire. These tires are great for lighter loads and highway use. Generally, they weigh less and cost less than a light truck tire and provide the vehicle with a smoother ride and better gas mileage. The downsides are that P-rated tires can't handle as much of a load as LT tires and they are more easily punctured.
LT stands for light truck tires. Terminology is a little confusing in the truck market because many manufacturers label their pickup trucks as heavy duty. Class 3 trucks such as the Ford F-350, GMC 3500 and Ram 3500, and smaller, are all considered light trucks. Medium duty refers to Class 4, 5 and 6 trucks such as the Ram 5500 or Ford F-650. That leaves heavy duty for the 18 wheelers and big rigs. That means LT tires are made for HD pickup trucks.
The common load-range ratings for LT tires are C, D and E. In the past, these ratings signified the actual number of plies the tire had. Today, the ratings are based on the maximum amount of pressure and load the tires can handle. The actual weight a tire can carry varies for a given load range, but in general a D-rated tire will handle a heavier load than a C-rated tire, and an E will handle more than a D.
LT tires will have a higher load rating than a P-metric tire. This adds stability to the vehicle for towing and hauling; it also adds durability to the tire, making it better for dirt and gravel roads as well. Rougher ride, reduced gas mileage and higher cost are all disadvantages of LT tires when compared to P-metric tires.
Tire Tread Types
Tires also get tread designations. Here's what those letters mean:
HT (highway terrain): HT tires are designed primarily for paved roads. They have shallow tread depths and very little or no shoulder and sidewall blocking. HT tires are typically fuel efficient and quiet. Since they don't need to offer high traction for off-road use, they can be made with harder compounds, decreasing rolling resistance, to last a long time. These are usually the most cost-effective tires because they have a lower purchase price, get better gas mileage and last longer than any other truck tire type.
AT (all terrain): AT tires are just what their name implies, tires designed to be good in as many conditions as possible. AT tires have deeper tread depths and significant shoulder and sidewall blocking. The tread has larger spaces or voids than an HT to allow mud and snow to clear out of the tire. If the vehicle spends time driving on logging and forest service roads, then an AT tire would be a good option. AT tires are a little louder than HT tires. They weigh a little more and get a little worse gas mileage as well. AT tires cost more than HT tires, but provide better all-around performance in bad weather and on dirt or gravel roads.
MT (mud terrain): MT tires are made for off-road use. They have the deepest tread depths and largest shoulder blocks. They also have bigger voids in the tread and sidewall lugs, allowing these tires to carry a vehicle through obstacles that would stop an AT tire. MT tires are noisy, heavy and reduce gas mileage. The deeper tread depth makes them more prone to uneven wear. This can make it difficult to keep them balanced over time. Generally, an MT tire will cost more than an AT tire will.
HP (high performance): HP tires are for street use and are rated for high speeds. They have shallow tread depths and sticky rubber, which provide excellent road grip. Generally they won't last as long or get as good gas mileage as an HT tire. While there are HP tires designed for rain and snow, most don't do as well in those conditions as nonperformance tires would.
UHP (ultra-high performance): UHP tires are similar to HP tires, but with an even higher speed rating. They provide better on-road traction performance than HP tires. They have the same negatives as HP tires, but to a larger degree and they cost more.
M+S (mud and snow): M+S tires are often marked with a snowflake on a three-peak mountain icon along with the letter designation. M+S denotes that the tire is approved by the Rubber Manufacturers Association for snow. The three-peak mountain with the snowflake means that the tire meets RMA's requirement when testing according to the ASTM International packed-snow traction test.
Within each tire tread type, there will be a variety of tires to choose from. In the AT tires you will find some that are borderline HT and on the opposite end some that are borderline MT. With so many options available there should be a tire that suits the needs of nearly any condition in which a vehicle will be driven.
Changing the tire size on a pickup, up or down, will certainly change its driving characteristics. Manufacturers optimize vehicles for the tires that are installed at the factory. Anytime the tire size or style is changed, the vehicle will perform differently from the way the manufacturer originally intended. On the positive side, that means you can fine-tune the performance of your vehicle for the types of terrain you're most likely to encounter. On the negative side, you can potentially create some unforeseen problems. Whether going with larger or smaller tires, the speedometer also will need to be adjusted in some way to display the correct speed.
Larger tires increase ground clearance, unsprung weight (meaning weight not carried by the vehicle's suspension) and allow the vehicle to roll over large objects easier, but the heavier weight of the tire has many negative effects. If larger tires are installed, expect steering, braking and suspension components to wear faster, offer lower gas mileage, slower acceleration and deliver longer braking distances. Be sure to consider that the center of gravity is also elevated, potentially reducing the stability of the vehicle. Finally, larger tires could require a complete suspension lift or fender modifications so know your vehicle's fenderwell limits.
When smaller tires are fitted, the exact opposite issues can happen. Fuel mileage might increase, the brakes, suspension and steering won't have to work as hard, and the center of gravity will be lower.
When shopping for new tires there are many variables to consider. The good news is that there are lots of tires to choose from. Compounds and tread patterns have gotten better over time as well, which means today's tires are significantly better than tires made 10 years ago.
Keep in mind that if you only need extra traction on rare occasions for ice and snow, then tire chains might be worth the investment, rather than using a set of dedicated winter tires. Folks who live in regions with longer, colder winters should consider having a set of winter tires and a set of summer tires.
Cars.com photos by Matthew Barnes, Evan Sears