Why do speedometers read high

Suddenly, a used Honda Civic starts to look a bit more like that Bugatti — for better or worse. For you. World globe An icon of the world globe, indicating different international options. Get the Insider App. Click here to learn more. A leading-edge research firm focused on digital transformation.

Good Subscriber Account active since Shortcuts. Account icon An icon in the shape of a person's head and shoulders. It often indicates a user profile. Log out. US Markets Loading H M S In the news. Chris Weller. Most speedometers max out around or mph, even though the cars aren't designed to go that fast.

Sat nav units — both portable and integrated into the car — calculate the speed of your car by measuring distance travelled over time using GPS satellite tracking.

There are, however, sat nav systems that use data from your car to integrate with the GPS signal to improve overall accuracy. Our best advice? When in doubt… better to stick to the speed limit if you want to avoid a penalty!

Your email address will not be published. Manage my appointment. Get your FREE valuation now. In a leased car, going over the lease limits could be quite costly.

Should we be worried that the odometer is also especially inaccurate? Concerned that your new car is faster than the speedometer says? Speedometers are designed to err slightly on the fast side, but your odometer should still be accurate, says Volkswagen. While speedometers are calibrated to fudge the numbers a little, odometers are designed to reflect accurate mileage, Tetzlaff says. The odometer shows the distance your vehicle has travelled, while the speedometer show how fast your vehicle is going.

Why is there a built-in factor of error for speedometers? Speed is a measure of distance over time. That's what the GPS is showing. But speedometers figure this out by measuring how fast the wheels are spinning using the speed sensor in the transmission. If the diameter of the wheels changes — and it does change, depending on tire size, pressure and wear — the accuracy of the speedometer gets thrown off.

Car and Driver wrote about this more than a decade ago, and their explanation still stands. The difference between actual speed and the speed dial tends to get noticed more with German cars because their speedometers are designed to never report a speed lower than actual speed.