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Tire Tech Information/General Tire Information

Speedometer Accuracy

Installing tires with a different overall diameter than that of your vehicle's Original Equipment tires may affect the accuracy of your vehicle’s speedometer and odometer.

If you followed the recommendations of our sales team or web site regarding tire sizing for your vehicle, this section is not applicable to your vehicle, as these recommendations are designed to maintain an overall diameter that is similar to your Original Equipment tires. If you purchased taller tires for your light truck or sport utility vehicle, you should verify your speedometer accuracy to avoid unnecessary meetings with the local constable.

Seconds Per Mile	Road Speed
50	72
51	71
52	69
53	68
54	67
55	65
56	64
57	63
58	62
59	61
60	60
61	59
62	58
63	57
64	56
65	55.4
66	54.5
67	54
68	53
69	52

The chart (shown left) is provided to help determine speedometer accuracy. If you're driving on a highway that has a mile marker every mile, it will allow you to determine your vehicle's exact rate of speed.

Follow the speed measuring instructions below:

1. Travel at a constant rate of speed on an open highway. Have someone record the number of seconds it takes to travel exactly one measured mile.

2. On the chart, locate the number of seconds it took your vehicle to travel one mile. The speed indicated next to the number of seconds is the true average road speed of the vehicle.

3. Repeat the measurement several times and average the results. Recalibration of your speedometer is recommended if significant inaccuracy is noted.

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