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• Brakes and Tires
• Dodge Ram

# Do bigger tires effect the speedometer How do you calculate the difference I had 30 inch tires and now have 33 inch tires?

Wiki User

2011-09-12 22:04:14

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YesPutting larger diameter tires on any vehicle will affect the speedometer and odometer readings. If you know the revolutions per mile for the original tires and the larger tires, you could calculate the speed difference. If they are already on the vehicle, you can also drive down the highway, set the speed at 60 MPH and measure the time it takes to drive between mile markers. One mile at 60 MPH takes 60 seconds. If it is not 60 seconds between mile markers, the difference is the speedometer error. AnswerYour tires are 10% larger than the car thinks. Therefore, you travel 10% more than your car recognizes. This has two effects:

10=11, 40=44, 100=110 etc.

Your actual mileage is 10% MORE than what your odometer is reflecting. (When your odometer reads 100 miles, you have actually traveled 110)

So when you see a cop doing a speed trap, remember to slow down accordingly.

When you sell your car, don't forget to disclose that you have larger tires and that the odometer should read more miles than it does.

2011-09-12 22:04:14