The car speedometer will estimates the vehicle's speed by measuring the number of revolutions per minute of one of the wheel or its transmission. If the car ha

The car speedometer will estimates the vehicle's speed by measuring the number of revolutions per minute of one of the wheel or its transmission. If the car has different-sized tires than the ones it was originally designed for, there may be some discrepancies between the actual speed vs the speedometer readings, which is why there is some leeway in the speed limit to account for that margin of error.