Why You Should Keep Your Work Truck’s Stock Tire Size
We love larger wheels and tires as much as anyone, but if you’re on the fence about going bigger—and especially if you use your truck for work—it’s best to stick with the factory tire size when the time for new rubber arrives. In an age where half-ton pickups are rated to tow 10,000 pounds or more, ¾-tons are regularly rated to lug 20,000 pounds and 1-ton trucks can tow north of 35,000 pounds, it’s never been more important to run the appropriate tires. In addition to properly sized tires being safer, acceleration and braking performance is preserved when you stay the course with the factory tire size. But the benefits don’t end there.
For one thing, new tires will be more affordable if you refrain from upsizing. And, arguably just as important as cost, factory sized tires won’t hurt your fuel economy or place added drag on the engine and transmission. Conveniently, you also won’t have to recalibrate the speedometer to read accurately, nor will the anti-lock braking and traction control systems be negatively affected. Convinced yet? Read on for our expanded reasoning behind all of the above.
Reason #1: Larger Tires Can Alter Performance
Everything your truck was designed to do was based off of the tire size it left the factory with. Your truck was designed, tested and sold to perform a certain way on that specific tire size—and changing it basically reengineers what automakers have spent millions (and even billions) of dollars on during that vehicle’s development. Trailer or not, payload or not, you can’t expect your new F-250 Super Duty to perform the same way it did with the factory 275/65R18 all season tires installed once you stuff 35-inch diameter tread in the fender wells.
Reason #2: Going Bigger Creates Other Problems
Larger diameter tires, which are also heavier than your factory tires, bring with them added rolling resistance. This not only means slower acceleration and added wear and tear on brakes, but your speedometer will require a recalibration to register vehicle speed correctly. Remember, the functionality of your speedometer, odometer, anti-lock brake system and traction control are all based on the use of that factory tire size. Larger diameter tires also create added strain for the transmission to deal with (especially the torque converter in automatics), as well as the driveline and even the steering system.
Reason #3: Sidewall Strength & Appropriate Load Index
Sidewall strength and load index are king when towing heavy, and your truck left the factory with tires that weren’t just specifically selected to handle its maximum GCWR, but that are overkill for the job. We agree that your late-model Ram 3500’s ability to tow 35,000 pounds via fifth-wheel hitch is incredible, but the tires your truck originally came with— its size, maximum inflation pressure and load index—was what the truck was tested with. Whether you notice it or not, larger tires and wheels throw much of the OEM’s R&D out the window, and they could even be unsafe if you attempt to tow heavy with aftermarket wheels and inferior tires under your truck.
Reason #4: Fuel Economy
It’s safe to say that no one wants to lose fuel economy. Unfortunately that’s all but inevitable when you install bigger tires. Even a minimal increase in diameter and/or width is detrimental to fuel efficiency. Two key factors that kill mpg are heavier tires and the reduced aerodynamics they bring with them. Larger, heavier tires are slower to get rolling and their increased overall diameter (as well as width in many cases) raises and widens your truck, making it less aerodynamic.
Reason #5: Affordability
In nearly all cases, sticking with your truck’s stock tire size will be the cheaper option. Using our 275/65R18 example from earlier, the typical cost for the popular Nitto Terra Grappler G2 in that size runs roughly $270 per tire. Bumping up to a 35x12.50R18 version of the same tire (a popular size many truck owners opt for) means spending more than $380 per tire. The cost savings alone in this scenario would be at least $440—and that fails to factor in the added cost of the leveling kit that might be needed to clear the 35s…
Reason #6: Handling & Stability
It’s obvious to most that with taller tires you get a higher center of gravity, but there is more to it than that. While not exactly dangerous, a truck that sits higher than stock (be it by tire size, suspension lift or body lift) is going to experience poorer handling and increased body roll. In short, the truck’s factory handling capabilities will be compromised. With nothing else being changed other than tire size (or tire and wheel size), a truck will also experience reduced stability when braking and cornering, especially at higher speeds.
If You Must Go Bigger, Do This:
As we’ve already mentioned, there is a time, place and correct application for bigger tires and wheels—but a truck that’s expected to live up to its factory maximum towing, payload and fuel economy ratings isn’t the ideal candidate. But be that as it may, enthusiasts are still going to choose to personalize their rides. So, if you have to have bigger tires under your truck make sure you match the factory tires’ load index or surpass it. Installing a bigger tire with a lower load index could affect the amount of weight your truck can tow or haul safely.
If You Must Go Bigger, Don’t Do This:
Don’t go for the stretched-tire look. This type of fitment is popular in today’s show truck scene, but making a tire rated for a maximum wheel width of 12-inches work on a 14-inch wide rim is extremely hard on tires. Specifically, stretched fitments place incredible stress on a tire’s sidewall as well as the bead, which makes them significantly unsafe when cornering at speed. On top of the reduced handling characteristics, stretched fitment also often leads to excessive tread wear.
More From Driving Line
- Not sure what load index is or where to find it on your sidewall? The ins and outs of this all-important load carrying capacity stat are covered right here.