By Bob Carpenter
Building heavy-duty (three-quarter-ton and one-ton) truck tires for use in the U.S. is a tough job for tire manufacturers. There are a wide variety of road surfaces, temperatures and elements in our 50 states, and that creates some unique challenges.
Most use computer simulation, on-road testing and customer feedback to arrive at a design that can handle the extra loads an HD truck is expected to tackle with the least amount of compromise.
When you start comparing HD tires to standard tires you will see features such as three-ply polyester casings, deeper tread depths and less tread void (the spaces between the blocks of tread).
To choose the right tire you need to know the gross vehicle weight rating of your truck. The GVWR is the maximum permissible weight of the vehicle (the curb weight plus all fluids, cargo, passengers, optional equipment and accessories). And you should know both gross axle weight ratings, which is the maximum allowable weight each axle assembly is designed to support as determined by the vehicle manufacturer. This includes both the weight of the axle and the portion of the vehicle's weight that is carried by that axle.
To help you educate yourself about HD truck tires (ideally, it should be a never-ending process), we have compiled this list of 10 things you should know about HD truck tires before starting your journey.
1. Inflation Counts
Under-inflated tires allow for too much sidewall flex, and that causes heat to build up in the tire. Heat is a bad thing for all tires, but worse for an HD tire that is expected to do serious hauling. Typically, HD tires have less resistance to heat buildup compared to passenger-vehicle tires. Plus, for every 10 pounds per square inch your tires are low (most HD tires will run tire pressures between 60 and 80 psi), your fuel economy suffers by 1 percent.
2. Matching Tires Matter
If one tire needs to be replaced while the other three are still in good shape, mismatching tread depths can potentially cause a problem with your differential. Slightly different tire diameters means the diff gets worked harder than it should and can lead to overheating and eventual failure. If you don't want to replace all four tires, there are places that can shave your tire to match the tread depth of the remaining tires. It might sound crazy to give up tread life on the new tire, but you could be preventing expensive driveline repairs.
3. Rotation Is Right
If your truck has four-wheel drive, then tire rotation is even more important than on a passenger car. The front and rear tires are asked to do different jobs while accelerating, braking and turning and therefore they wear differently. Rotating the tires at the recommended intervals will give you more service life. Also, if you carry a full-size spare you should include that tire in the rotation so that all five tires wear similarly. That way when you have to use the spare it will be more closely matched to the other three tires.
4. Tires Can't Increase Your Payload Capacity
If you install tires that are more capable than the ones that came on your truck from the factory, that does not increase the load-carrying capability of your truck. Just because the tires are tougher doesn't mean that the axles, shackles, springs and other parts can handle the extra weight.
5. Tire Information Placard
Inside the driver's door (usually), there's a sticker that tells you the GVWR for the whole truck and the GAWR for the front and rear of your truck, the size tires that came on the truck and the amount of tire inflation the manufacturer recommends. The manufacturer can't install tires that don't meet these minimum specifications. And you shouldn't either.
6. Tires Leak
Over the course of a month, most tires will leak about 1 to 1.5 pounds of air pressure. It's lost through the natural permeation of air through the rubber. If you go several months without checking your tires, we can almost guarantee they will be low. Additionally, they will have leaked at different rates so your numbers could be all over the place.
7. Cold Tire Pressure Check
Check the tire pressure on your HD truck tires when they are cold (meaning ambient temperature). For every 20 degrees increase in temperature of the tires, the inside air pressure can go up 2 psi. Our advice: Check your tire pressure once a week in the morning before you head out. Monday is a good day to start the week out with your tire pressure correct.
8. Replacing Two Tires
If you are replacing only two tires, move the remaining pair of tires to the rear axle and put the new tires up front. You want the most tread on the front of the truck to avoid hydroplaning in bad weather. Plus, according to some experts, most people can recover more easily from loss of traction to the front tires (understeer) than they can from loss of traction to the rear tires (oversteer).
9. Tires Are Speed Rated
A "Q" rating means that tires should not exceed 99 mph. An "R" rating allows for up to 106 mph, and an "S" rating will get you up to 112 mph. There are higher ratings, but, really, do you need to know about them? Note that driving in excess of the tire's speed limitation (even if properly inflated) can lead to a catastrophic tire failure. Most truck tires are "R" rated.
10. Break-In Period
Tires are made out of different materials (rubber, steel, fabric, etc.) and when they are built in the molds, there's a release lubricant used to make it easier to get them out. All components need to break in over time, and the release lubricant needs to wear off before your tires can perform to their best levels. Some experts say you should drive the first 500 miles with easy acceleration, easy braking and smooth cornering. Also be aware that brand new (and stiffer) tread doesn't respond the same way as the worn (softer) tread you took off the truck. The tires may be a little slower to respond than you're used to since the tread is likely to squirm a bit until it wears in properly.
Cars.com photos by Bob Carpenter; manufacturer images