Pros & Cons Of Larger Tires

What you gain off road, you lose on economy

Published in the July 2019 Issue July 2019 Ask The Expert, Feature Steve Janes

Before you decide to throw on larger tires, you may want to weigh the benefits and drawbacks that come with going big. After all, there are researched, tested and proven reasons truck manufacturers choose to put specific sized tires on their vehicles. Just because something “looks cool” doesn’t mean it’s smart.

However, recognizing that OEMs design vehicles for “the most practical uses” doesn’t necessarily mean you are an average user with common needs. You may look to your truck to provide unique operating characteristics that require some modifications to basic OEM design features.

Diesel Tech Magazine reached out to Aaron Conrow, truck tires product manager at Cooper Tires, to get some feedback from a tire expert on the pros and cons of going big on the wheels.

“Truck owners looking to increase the size of their tires on their diesel trucks have a lot of options to consider, and should carefully weigh both the advantages and disadvantages of sizing up,” Conrow explained.

The size of the tire does affect the performance of the truck, sometimes in a good way, sometimes in a not-so-good way. 

“While increasing the size of the tires on your truck can offer some immediate and well-known benefits such as a more customized appearance of the truck or even better visibility with the increase in height of the truck, there are many other potential advantages to be considered as well,” Conrow said.

Advantages

Perhaps one of the more popular reasons to go big on the wheels is to increase your ground clearance, which can be important in off-road driving conditions.

“Often truck owners want to increase the size of their tires to provide greater ground clearance,” he said. “This is especially common in the off-roading community, where 40-inch tires have become increasingly popular over the past several years as off-road adventure seekers look to tackle ever more challenging terrain and ever larger obstacles.”

Conrow said that by increasing the tire’s sidewall length or aspect ratio, the off-road enthusiast has more sidewall to grip onto large rocks and boulders encountered on more extreme trails.

“Beyond those benefits, truck owners who ‘plus up’ or change out their tire from a stock tire may see improvement in towing capability through improvements in load-carrying the tires can handle (a higher load range),” Conrow explained. “Towing heavier loads with a stock suspension and stock tires will often make your truck ‘squat’ down on the rear axle, which can make bottoming out more likely when encountering bumps with a heavy load over the rear axle.”

According to Conrow, taller and wider tires typically have deeper, wider tread than stock tires, which can improve performance in mud and soft surfaces, with the added width also providing better acceleration on dry pavement.

“As diesel engines develop more torque than typical gas engines, wider tread patterns can prove particularly helpful to diesel truck owners seeking extra grip,” he said. “That extra diesel torque can also cause tires to wear more quickly, so going with a wider and deeper tread enables the tires to last longer and be replaced less frequently.”

Disadvantages

But with the good, there comes the bad … or the trade-out you must recognize when you change from the OEM specifications. After all, you can’t just throw on larger tires without making a few other modifications to match the wheel size.

“Beyond the cost of a lift kit and/or new rims (which can be expensive), the deeper, wider tread that provides performance benefits may actually reduce the truck’s fuel economy,” Conrow explained. “Since a larger tire is heavier, it experiences what the tire industry refers to as ‘increased rolling resistance.’”

So if you are going to be spending a lot of time on the highway, you should definitely factor this in to your considerations. “Not to mention, the deeper tread depth, especially if the tread design is meant for mud use, can make the tire significantly louder than a shallower depth, all-terrain design,” he said. “We’ve all heard or experienced the distinctive hum of a mud tire headed down the road.”

Conrow said the handling of your truck may also change, since larger tires and a lift kit will change the center of gravity of your truck.

“Don’t be surprised if you experience more body roll in sharp turns or emergency lane-change maneuvers,” he explained.

Finally, Conrow pointed out that if you change out your tires from the original, stock size you will likely need to recalibrate both the truck’s odometer and the Tire Pressure Monitoring System so they can accurately reflect the vehicle’s speed and appropriately monitor the inflation pressure of the new tires.

“Also, be sure to check with the truck manufacturer about your warranty policy,” Conrow said. “Some manufacturers won’t warranty a truck that has suspension modifications.”

 

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