Here’s a surprise: your car’s speedometer is almost certainly not showing your true speed. By law it can read high but never low, so most gauges run 2–10% optimistic. Here’s how to check yours — and why a head-up display helps.
Why speedometers read high
Manufacturers build in a safety margin so you’re never accidentally speeding due to a low reading. Tire wear and aftermarket wheels shift it further.
Check it in 2 minutes
Compare your dashboard speed to a GPS reading at a steady pace. Or just use our Speedometer Accuracy Calculator — enter both numbers and it shows your true speed and the error.
The fix: a GPS head-up display
A GPS head-up display projects your true, satellite-verified speed onto the windshield, so you always know your real pace without looking down.
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