Why the speedometer can show the wrong speed: the main reasons

Why the speedometer can show the wrong speed: the main reasons

Many drivers have found themselves in situations where the actual speed was higher or lower than what was shown on the speedometer. The fact is that even the factory allows a small error in speed indicators, and this can play a cruel joke with drivers, who are literally a few kilometers over the speed limit will be fined with the help of cameras, photo and video recording of violations. Let’s talk in detail about why the real speed may be different from the speedometer. You can find out the terms and conditions for recycling your old car here: https://scrapcar.cash.

Why a car’s speedometer can show incorrect speed: the main reasons

Ways to measure vehicle speed

There are several ways to measure the speed of the car, but most systems read the number of revolutions of the transmission shaft. However, in certain cases, such figures will differ from the actual number of wheel revolutions. In such a case, a small error both upward and downward is allowed.

Experts note three types of errors, which may directly affect the speedometer readings:
1. instrumental related to possible malfunctions of the speedometer itself, for example, it has a wrong scale graduation.

2. Methodological errors are due to imperfect measurement methods used.

3. Additional errors are due to various other factors affecting the accuracy of such indicators.

By the way, the factory allows only a positive error in the speedometer indicators. That is, the speedometer dashboard will show only higher speed than in reality, but not less. However, some malfunctions of this system may appear in the process of operation of the car or the car operation conditions may influence the accuracy of the readings. This leads to negative errors, when the speedometer shows less speed than the actual speed, which may result in violation of the speed limits set on the road.

What is the cause of car speedometer errors?

Factors contributing to inaccurate speedometer readings
The most common cause of such speedometer errors is the use of wheels with a larger diameter than recommended by the manufacturer. Increasing the radius of the wheels invariably leads to speedometer inaccuracies, and such readings may differ by 10% or more.

Also inaccuracies may be noted if the pressure in the tires differs significantly from the optimum. In such a case, the speedometer discrepancy may make up 2-3 per cent. By the way, worn tires may also affect the speedometer readings, in such a case, small wheel slippage is often noted, which leads to a significant increase in the speedometer readings.

Remember that in order to ensure that the speedometer readings are as accurate as possible, it will be necessary to consider the manufacturer’s recommendations for wheel size. Using only new quality tires, which constantly check the pressure readings, which should meet the optimal parameters.

What is the cause of the appearance of errors in the car speedometer?

To summarize.

Such situations, when the speedometer readings differ significantly from the real speed of the car, occur quite often. There are several reasons for this, this is both inherent in the factory error, and the use of the motorist non-standard increased in size wheels, which, moreover, have a worn tread. To reduce such errors as much as possible, you should use wheels and disks of the size recommended by the manufacturer, and you should also change the tires regularly, avoiding the use of the car on tires with worn tread.

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