How GPS Speedometers Are More Accurate Than Car Speedometers

When you are driving down the highway, you likely trust your car's dashboard speedometer completely. However, most drivers are unaware that factory-installed speedometers are intentionally designed to be inaccurate. In contrast, modern GPS speedometers offer a level of precision that mechanical systems simply cannot match.

The Flaw in Mechanical Speedometers

Traditional vehicle speedometers do not measure your speed directly. Instead, they measure the rotation of your vehicle's tires or the transmission output shaft. This mechanical calculation assumes your tires are a specific, perfect size. But in reality, tire sizes change constantly:

• Tire Wear: As tires wear down, their circumference shrinks. A smaller tire has to spin faster to cover the same distance, causing your dashboard to show a higher speed than actual travel.
• Tire Pressure: Under-inflated tires have a smaller rolling radius, which leads to an artificially high speed reading.
• Manufacturer Bias: By international laws (such as UNECE Regulation 39), car manufacturers are strictly prohibited from under-reporting speed. To avoid lawsuits, dashboards are calibrated to read 3% to 7% higher than true speed.

How GPS Telemetry Solves This

A GPS speedometer completely bypasses mechanical components. Instead of counting wheel rotations, it communicates with satellites. Our web-based Live GPS Telemetry uses advanced physics to calculate velocity.

Conclusion

For the vast majority of daily driving and highway cruising, a GPS speedometer provides the most honest and accurate reflection of your true speed, entirely free from mechanical biases.