Do Larger Truck Tires Lower MPG?
A common question is: what impact does tire size have on fuel economy? In order to understand the difference when installing larger wheels and tires, also known as plus sizing, it is necessary to test different kinds of wheel and tire combinations on a truck in order to see what impact the larger tires play in fuel economy.
Truck Tire Size
Larger and thicker tires can significantly increase traction, as more tire means it has more road to grip onto and it also means there is less wear and tear on the tire due to it taking fewer rotations to drive down the same allotted path as a smaller tire. That being said, this is just a subtle comparison between smaller, entry level tires on a smaller truck. This compares a wheel size of 235/35R, 225/40R, 225/45R, 205/55R and 195/65R (larger current Chevy trucks such as the current Colorado and Silverado have larger tires than this, but this test is done on an earlier model in order to show the comparison for both current models and older vehicles many people are still driving.
Difference in Fuel Economy
First, the 195/65R used a 15 x 6 inch wheel. This is the smallest wheel and tire combination tested. It offered an average fuel economy of 23.3 miles per gallon. The next larger size of 205/55R used a 16 x 7.5 inch wheel. The average fuel economy sat at 22.9 miles per gallon with this one. The 225/45R came with a 17 x 8 inch wheel and it provided a 22.8 average fuel economy. The 225/40R came paired with an 18 x 8 inch wheel and provided 21.9 miles per gallon fuel economy. The last tire and wheel size is a 235/35R and features 19 x 8.5 inch wheels, which saw the fuel economy drop to 21.1 miles per gallon.
Beyond this, the specs change as well. It took the smaller tires a total of 7.6 seconds to reach 60 miles per hour while the larger wheels took 7.9 seconds. The one advantage that came with the larger tires is the improved braking. When traveling 60 mph, it took the smaller tires 130 feet to completely stop while this dropped to 126 feet on the larger wheels.
Size and Weight of Truck
The difference is not only in size, but also weight. Larger wheels and tires add more weight to the vehicle, which is going to slow it down somewhat. However, there is a way around this. If my current vehicle uses steel wheels and tires, I can actually swap out the steel wheels for alloy wheels and upgrade the tires to something larger. Because alloy is far lighter than steel, it shaves a substantial amount of weight off the vehicle, whereas larger tires do not add that much more weight (especially if only going up a few inches in size). So, in theory, if my vehicle is using heavier wheels, I can make a change to larger tires and lighter wheels and actually improve my fuel economy, all while cutting my braking distance as well.
For anyone who is looking to purchase larger truck tires, they are going to suffer a drop in fuel economy, but it is possible to offset this with lighter wheels, if lighter wheels are available.