Do Bigger Tires Affect Your Truck’s Transmission?

Adding bigger tires to your truck may make it look a lot cooler. However, there’s more to adding bigger tires than simply upgrading your aesthetic. Big tires and lifted trucks have quickly become a part of American culture. And having the biggest, baddest truck on the road is the goal for many drivers. 

Unfortunately, there’s one issue many truck owners tend to overlook when upgrading. If you want to give your truck a larger footprint, do it the right way with the proper knowledge. Let’s take a moment to dig a little deeper into the subject. 

Can Bigger Tires Cause Transmission Problems? 

In short, yes. You have to think about all the parts of your truck that have something to do with the tires. When you increase the size of the wheels and tires on your truck, you change the ratio of all the components working together to make your truck stop and go. 

The drivetrain, the transmission, and the braking system are all affected when you shift the ratio by adding a larger circumference tire to your vehicle. So are your odometer and speedometer. Your vehicle’s transmission was designed to work on a certain rotation. Changing the rotation means you’ll need to regear your axle to the proper specs. 

What Happens If You Put Bigger Tires on Your Truck? 

Many different things happen when you put bigger tires on your truck. It’s kind of a ripple effect, really. Changing the tire circumference changes the gear ratio for your transmission to the road. This causes your vehicle to require more lower-end torque to turn the wheels and the engine will spin slower. 

This slower spinning engine will cause slower acceleration and more heat in your gearboxes. The vehicle will also travel further per tire rotation which affects speed and sensors.

Changing the tire size will also affect your truck’s differential. How your vehicle grabs on the road will change, affecting towing and loaded performance. You should know that properly upgrading your wheel size means you’ll have to invest a bit of money into your truck. 

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Do Bigger Tires Affect Speed?

Bigger tires don’t make you go any faster on the roads, but they will affect your speedometer reading. Think about it. A larger circle will go a longer distance than a smaller circle with each rotation. Your vehicle’s odometer will report that you’re going a bit slower than you are actually traveling. You could rack up a few unwanted speeding tickets if you don’t take the time to recalibrate your speedometer. In fact, our truck’s speedometer reads 25% lower than the actual speed because of the tire size.

Do I Need to Lift My Truck for Bigger Tires? 

Whether or not you need to add a lift kit to your truck depends entirely upon just how big you’re planning to go with your wheels. The lift kit addition would only be due to the lack of clearance. 

However, raising your truck higher off the ground won’t do much to help your transmission absorb the change. If you’re not increasing the radius too drastically, you may not even need a lift to make the change. 

What Modifications Should Be Done With Large Tires

A tire upgrade and additional modifications will really depend on the vehicle and what it’s being used for. For example, a truck that is going to be used for off-roading and will not haul or tow can usually run with no modifications to the drivetrain besides a speedometer calibration. However, acceleration and on-road performance may be reduced.

For trucks that still need to work with larger tires gearing changes are almost always required. For example, we once had a fifth wheel shipped and the shipper showed up with a newly modified truck with oversized tires. He had never towed with it before and we warned him that his truck needed modifications. Sure enough, 1000 miles down the road his differential burned up and he broke down in the middle of the desert.

Re-gearing the differentials of a truck can better match engine and transmission speed to the new tires. With steeper gearing, the engine will turn faster and everything will operate better if used for heavier applications.

Our current off-road truck is a RM 5500 that had very steep gearing for heavy loads to begin with. The oversized tires make little difference to the operation as we no longer haul 30,000 lbs trailers, but only carry a truck camper. If however, you have a truck with lower gearing as many of them come now, the differentials should be upgraded with wheel size.

Is It Bad to Drive With Different Size Tires? 

Different size tires from the factor spec can put additional stress on your vehicle’s drivetrain. If an owner installs larger tires and does not re-gear the vehicle it can cause excessive wear. If a truck is not used for heavy hauling or towing applications it may be minimal as it will “think” it’s working harder all the time. However, if a truck with oversized tires is worked hard and used for towing without additional modifications damage can occur.

With regard to different size tires mounted on the same vehicle, yes it’s usually bad. While you can drive with slightly different-sized tires in a pinch, we don’t advise doing it long-term. It’s always best to have four matching tires of the same brand and size. Otherwise, your tread will wear unevenly, changing how your vehicle handles various road conditions. Mismatched tires also put stress on your transmission, suspension, and braking system.

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Will Smaller Tires Affect My Transmission? 

Smaller tires can also affect the performance of your vehicle’s transmission. The transmission needs a specific circumference. Changing the circumference will change the needed gear ratios inside your transmission or differential. 

Smaller tires will also affect the accuracy of your speedometer and odometer. They can also cause your brakes to malfunction and create issues with the transmission shifting. Smaller tires may even cause your check engine light to illuminate. 

In general smaller tires are less common and tend to be less of a problem than larger tires.

Is It Worth Putting Bigger Tires On My Truck?

The question of worth comes down to what you hope to achieve with your larger tires. There are some notable perks to having large ones on your truck. That includes added clearance when offroading, a better grab in muddy situations, and the sheer intimidation factor. 

However, the real question is whether or not the larger tires will help you enjoy and utilize your truck more effectively. If the way you intend on using your truck aligns well with the upgrade, all the money you put into doing it properly is “worth” it. 

The money spent may be better allocated elsewhere if you’re just trying to put big tires on your truck to impress your buddies. Regardless of your intentions, you want to make sure the bigger tires aren’t the only change you make to your truck. The cool look won’t last long if the transmission and brakes can’t keep up with the changes. Be safe, and do the work right.

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