I drive a SsangYong Musso, and the speedometer consistently reads a few miles per hour above my satnav. I have always believed that the satnav would be the most accurate and reliable, but I recently ...

Speedometer: Aftermarket modifications, such as different tire and wheel sizes or a change in the differential gearing, can cause speedometer inaccuracy. GPS: These devices are positional speedometers ...

Q:I operate two vehicles with two different aftermarket GPS systems, each gives me conflicting speed readings in relation to the vehicles' speedometers. Which is more reliable, the factory installed ...