Speedometer Reading Faster Than Actual Speed? (8 Reasons Why)

Since cars are moving vehicles, every car that you see will be equipped with a speedometer to help drivers know how fast they are driving. While speedometers are usually accurate, they can give false speed readings.

You may be wondering why your speedometer is reading faster than your actual speed. I did some digging, and here is what I learned!

Speedometer Reading Faster Than Actual Speed?

Generally, your speedometer will be reading faster than the actual speed because of a problem with your tires. If you got tires that have a bigger or smaller diameter than usual, it would affect the speedometer’s readings. Additionally, issues with your speed sensors, speedometer cables, or the manufacturer’s design can impact the speedometer’s readings.

Do you want to know more reasons why your speedometer is giving inaccurate readings? I made a list of reasons below, so keep reading!

1. Bigger Tire Diameter

One of the most common reasons why a speedometer would give you higher readings is that you recently changed your tires.

Typically, this will occur because you got tires that have a bigger diameter than the tires that your car originally came with.

When you get tires with a larger diameter, the tire’s pressure will increase, which will make your speedometer read faster.

2. Smaller Tire Diameter

Similar to increasing the size of your tire’s diameter, getting tires with smaller diameters can make your speedometer read faster than the true speed.

If you got tires that were smaller than your car’s original set of tires, the new and smaller tires will have to work harder to match the same speed.

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So if you think that you are driving at your normal speed, but your speedometer is reading faster, it is because you have smaller tires that are rotating more than your old tires.

3. Road Conditions

Another common reason why your speedometer would give inaccurate readings is that you are driving in new road conditions.

Generally, most cars that you buy are meant to drive over streets because they are not built for off-roading.

Additionally, the tires that come with most standard cars will not be suitable for off-road driving.

Typically, your speedometer makes speed readings by measuring how many rotations your car’s wheels make.

When you go off-roading or drive on bad roads, your tires can rotate faster, which will lead to faster speedometer readings.

Usually, your speedometer will give you accurate readings once you drive on normal roads since bad roads will be a temporary miscalculation.

4. Worn Down Tires

Worn Down Tires

As stated earlier, opting for tires with smaller diameters can affect how accurately your car’s speedometer works.

If you have not changed your tires recently, you can still have smaller tires that affect the speedometer.

Generally, car tires are made of rubber, which helps the car grip the road, but the rubber will lose efficiency and size with time and use.

All tires will eventually face some wear and tear as you use them, and how quickly they wear will depend on how you drive, where you drive, etc.

Since the tires would be smaller, the tires would make more rotations and make your speedometer read faster.

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5. Faulty Sensor

Depending on the type of car that you have, your speedometer may be reading faster than the actual speed because you have a bad sensor.

Some cars utilize a digital speedometer, which uses a speed sensor to measure how fast you are driving.

Typically, the speed sensor is on one of the transmission’s gears, and the sensor will measure the car’s speed by how the gear spins.

Once your sensor goes bad, your sensor will not be able to accurately read how fast your gear is spinning.

6. Bad Speedometer Cables

Normally, some cables are attached to your speedometer to deliver the speed readings to your car’s dashboard.

Occasionally, these speedometer cables can get damaged, which can occur due to a collision, rodents biting on them, etc.

Once the speedometer cables are damaged, they may deliver false readings to the speedometer.

Generally, you can fix this by replacing the speedometer cables in your car with new ones.

7. Speedometer Is Not Properly Calibrated

Typically, purchasing a car will have the speedometer calibrated properly to the car’s factory specs to give drivers accurate speed readings.

If you have recently modified your car, there is a chance that your speedometer will need to be recalibrated.

For instance, we mentioned earlier how a change in tire size can affect the speedometer.

If you want to keep the new tires despite the difference in size, you will have to recalibrate the speedometer to work with the new set of tires.

Otherwise, the speedometer will still be calibrated to the previous tires’ sizes, which will give you inaccurate speed readings.

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8. Car Design

Sometimes, the reason your car gives you faster speedometer readings is that the manufacturer designed the speedometer that way.

While some car manufacturers give accurate speed readings, others may calibrate the speedometer to read as much as 10% higher than the true speed.

Generally, this is done as a safety feature to make drivers think that they are driving faster than they actually are.

That way, drivers may be less inclined to go over the speed limit because they think that they are already driving fast.

Conclusion 

Usually, speedometers read faster than the actual speed because there was a change in your tires, which is normally the size of your tire’s diameters.

Having smaller or larger tire diameters can affect how the speedometer would read the tire rotations.

Moreover, some car manufacturers calibrate the car’s speedometers to read up to 10% higher than the true speed to keep drivers from speeding.

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