# Do Bigger Tires Affect Speedometer? (Your Full Guide)

There are several reasons you may want to change the size of your tire, but if this occurs, you’ll likely have a problem with your speedometer, particularly if you purchase larger tires.

But if you’ve never changed the size of your tires before, you may wonder exactly how bigger tires affect your speedometer? If you’d like to find out, keep reading!

## Do Bigger Tires Affect The Speedometer?

Bigger tires will trick your car into thinking that it isn’t traveling quite as much, therefore causing your speedometer to read incorrectly. Fortunately, car companies are aware that drivers change their tire size and, therefore, have provided ways for you to fix this issue. However, be sure to fix the speedometer before switching your tires.

If you’d like more information on how to fix a speedometer after switching to large tires and more, keep reading for more useful facts and tips!

### How Do You Fix a Speedometer After Bigger Tires?

Luckily, tire companies understand that many people may choose to switch out their tires for larger tires. Therefore, most vehicles have an innate system to help you fix your speedometer after switching tires.

Usually, you can simply press the calibration button down and then drive the recommended distance, and this way, your car will automatically accommodate the bigger tires. However, this feature only works for an electrical speedometer.

For a mechanical option, you’ll need to locate your transmission and count the number of teeth present.

Next, you’ll need to calculate the number of tire revolutions per mile, which you can do by using the following method:

1. divide 20,168 by the diameter of the tire
2. multiply the divided number by the number of teeth on the transmission (the axle’s ratio in your user manual)
3. Next, divide the number by 1,001
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The final number in your equation is the number of teeth you need on the driving gear to give your speedometer accurate mileage.

Next, you’ll need to locate the part with the right number of teeth that is also suitable for your car, which should allow you to choose the correct piece for your car.

Afterward, you’ll need to replace the part and then your car should start stacking up miles correctly.

### Does Changing Wheel Sizes Mess Up the Speedometer?

Any time you change the tire size on your vehicle, you will inadvertently change the speedometer.

Your car’s speedometer works by counting tire revolutions, so if your tires suddenly switch sizes, they won’t be counted accurately.

Therefore, if you ever switch the size of your tires, then you’ll need to adjust your speedometer as well.

### Do Bigger Tires Affect MPG?

Bigger tires will decrease your fuel economy because they’re heavier, while smaller tires will increase fuel economy.

Furthermore, small tires also have a higher rolling resistance, which will cause them to need more energy to get rolling, affecting your MPG overall.

However, other things related to the tire will also impact your fuel economy. For instance, the tread will matter, so don’t just look at the size of your tire, look at everything that affects MPG.

### How Will Bigger Wheels Affect My Speedometer?

Bigger wheels will make it seem like your car is driving fewer miles. If your wheels are bigger, they won’t rotate nearly as much. Therefore, your car will think that you’re traveling less.

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Luckily, you can fix your speedometer to recognize the bigger wheels, which is essential to prevent your car’s speedometer from reporting inaccurate numbers.

To know more about tires, you can also read our related posts on what are forged wheels, speed rating H vs. V, and if tires affect gas mileage.

### Conclusion

Bigger wheels go through fewer revolutions to travel the same distance, meaning your speedometer will assume that you are traveling fewer miles.

For this reason, it’s highly recommended to adapt your speedometer when changing your tires so that it doesn’t get confused.