So you’ve decided to toss aside the wimpy all-seasons that came with your truck in favor of meaty, chunky all-terrain tires. That’s excellent – but how do you know what size tire you can upgrade to?
There’s a lot to that question, and we’ll answer it fully in a moment. But be forewarned that there’s more to upsizing your truck tires than you might think. Gas mileage, handling, braking distances, turning radius, ride quality, and even speedometer calibration are all among the ramifications of changing to larger tires.
Don’t be discouraged, though. With the right research, you’ll know exactly what to expect when you go to buy those gnarly off-road tires. Keep reading and we’ll give you the lowdown on what you need to know.
What’s the Largest Size Tire I Can Fit on My Truck?
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First, the short and sweet answer: generally, most unmodified trucks – that is, they retain the factory suspension settings – can swallow tires with a diameter of up to 33 inches. Beyond that, you’re likely to run into clearance issues as well as tire rub during cornering.
The more detailed answer is that you’ll need to make a variety of measurements in order to precisely determine what size tire you can safely fit. There’s a number of measurements to take, and you’ll want to make sure you’re taking accurate measurements before purchasing your tires.1 The goal is to determine all the relevant clearances in all situations, from the steering wheel at full lock to the suspension at a full rebound.
If all the measuring sounds tedious, you can try a tire size calculator, such as this one from tiresize.com. It requires knowing the tire size – which is emblazoned alongside all tires in a ‘XXX/XX/RXX’ format – but armed with that information you can see the height in inches of the tire you’re considering. If you’ve done your measurements and figured out how big you can go, this calculator makes it easy to see which tires fall within that threshold.
And if you have no information but just want quick facts? Make sure you’re finding the right measurements – Especially if you have an older truck; older makes and models are typically modified with larger tires.2
How Will Larger Tires Affect My Truck?
As we noted earlier, installing larger tires has implications beyond looks. Larger tires come with numerous drawbacks, ranging from diminished gas mileage to speedometer inaccuracy. We’ll go over the various consequences individually:
Tires have always affected gas mileage. Rolling resistance, or the tire’s propensity to resist motion, increases as the tire tread becomes beefier. Think about the racing slicks used in NASCAR versus all-terrain tires found on off-roaders: the racing slick hardly provides any traction outside of a racing circuit, while the all-terrain tire grips like glue anywhere. The racing tire has almost no tread resistance to overcome, which is bad for initial grip – making drama-free launches unlikely – but excellent for high-speed cruising, where less effort is needed to overcome rolling resistance. Though it isn’t exactly top of mind for a racing team, such little rolling resistance makes for better gas mileage.
Truck tires are the opposite: their large size and fat tread are like a dog resisting a tug on the leash: they don’t want to go forward. Overcoming their additional rolling resistance requires more effort on the part of the drivetrain, thereby reducing gas mileage.
In short, the bigger your tire and the fatter the tread, the worse your gas mileage will be. This is especially the case with the sort of all-terrain tires commonly fitted to trucks by enthusiastic owners.
Ride and Handling
Your truck’s tires are where the rubber literally meets the road; as such, no single change to your vehicle has a greater impact on ride and handling than new tires. The tread design, the chemical composition of the rubber, and the physical size of the tire all play an important role in determining how your car steers, brakes, and handles.
In the realm of pickup trucks and SUVs, bigger tires don’t bring many benefits in this regard. Going up to 33-inch all-terrain tires raises the overall ride height of the truck even if the suspension is factory stock; the added height means a higher center of gravity, which results in more body roll in corners. Corners you took comfortably at, say, 40 mph with all-seasons might require a 35-mph approach with 33-inch tires.
Braking is also adversely affected, as the bigger tires require more effort to slow down. Go big enough – bigger than even 33 inches – and you may want to consider upgrading your braking system to cope with the larger tires.
Larger truck tires almost invariably result in more road noise than the factory all-season tires. This is again due to the tread design, which isn’t designed for the ultimate in comfort but rather the ultimate in capability. If you’ve experienced the incessant hum of snow tires, you’ve gotten a taste of what all-terrains will be like.
This is something that becomes more pertinent as you get further and further away from the factory tire size. When the manufacturers calibrate the speedometer of a vehicle, one of the most critical factors involved is the physical size of the tire. That’s because the actual tire size has a direct bearing on the speed achieved; at the same engine speed and with the same gearing, a physically larger tire will be traveling faster than a smaller tire. This is due to the fact that a larger diameter tire travels further in one revolution than a smaller-diameter tire.
If you buy a larger tire but don’t adjust your odometer and speedometer accordingly, you will actually be inaccurately recording your distance traveled and current speed. And because the speedometer of your truck would be underrepresenting your current speed, you’re more likely to get a ticket.
For smaller tire upgrades, this isn’t much of a concern – the differences are minute. But if you jump up significantly in your tire size, you’ll want to bring your truck to a professional mechanic who can adjust your speedometer and odometer to accurately reflect your new tires.
Are There Any Positives To Bigger Truck Tires?
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Yes, actually, despite the concerns we just laid out. For one thing, bigger tires provide increased ground clearance, making it easier to tackle trails, scurry over boulders, and ford small streams. If it’s the backcountry you pine for, bigger tires will help you get there without issue.
Larger all-terrain tires also provide better grip in the traditionally low-traction environment. Mud, sand, snow – whatever the conditions, an all-terrain tire will live up to its name. Where all-seasons are left hopelessly spinning themselves silly, an all-terrain will calmly drive on past.3
Another overlooked benefit of larger tires is that they can actually improve towing capacity, due to the additional rubber contact with the road and their higher maximum load rating. Be careful though, as the payload and tow ratings set by the manufacturers look at many other factors than tire load when determining a truck’s maximum capabilities.
And then there’s the aesthetic. Who doesn’t think truck tires immediately ratchet up the cool factor on whatever they’re mounted on? For many people, that’s reason enough to look past the drawbacks and the expense of an upgrade to all-terrains.
Bigger tires look cool and do wonders off-road, but they come with drawbacks that can’t be overlooked. If you’re in the market for bigger tires, consider why you want them in the first place and be sure you’re ready to accept the drawbacks such an upgrade entails – drawbacks that, if your truck is your daily driver, you’ll have to live with every day.
If you’re still set on upgrading, use the sources we linked to above to determine the right size tire for your truck. And if you want more reassurance before pulling the trigger, visit the social media groups or internet forums for your specific make and model. These communities are often treasure troves of highly specific information, and spending a little time there is bound to give you the answers you’re looking for.
Once you’ve figured out what size tire is right for your truck, you’ll be ready to explore our guide on the best truck tires.
Ride Digest uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
- Skoropad, M. The Biggest Tires You Can Fit on Your Truck. utires.com. Published 8 Dec 2017. Accessed 28/Sept 2021.
- Cray, A. Tire Size Guide – Does it Hit or Fit? offroaders.com. Published 27 Sept 2021. Accessed 28 Sept 2021.
- Tips To Keep Tires Cool During Summer. Consumer Reports News. Published 7 Aug 2018. Accessed 24 Sept 2021.