Speedometers often show inflated speed data, and manufacturers deliberately allow this error, Lev Zimanov, an associate professor of the Department of Motor Transport Operation and Car Service at Moscow Automobile and Road State Technical University, said on Sputnik radio.
The device always overestimates the speed of the vehicle by a minimum of 5%, a maximum of 10%. If the speedometer read incorrectly, manufacturers could face lawsuits from owners who would be fined for speeding and the speedometer not matching the car’s actual speed. Therefore, manufacturers put a possible error in the direction of exaggerating the readings.
He added that the accuracy of the speedometer readings can also be affected by the diameter of the tires and the degree of wear.
The correct speedometer readings are based on new and fully inflated tires of the maximum size allowed. During operation, the tires are erased a few centimeters, and only their wear allows the speedometer to cheat 2-3%.
Smaller wheels mean you have to rev more to cover the same distance, and most speedometers don’t record the speed itself, but the rpm of something, say the transmission output shaft or the left front wheel.
On the other hand, if you put wheels with a larger diameter, the speedometer can theoretically underestimate the speed.
To know the speed quite accurately, you can use special devices that work through satellite systems. But this isn’t just a function in the navigator, the values there aren’t that accurate. Riders use separate instruments, accurate speedometers.
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Source: Z R
