Speed and odometor

I have a car 1997 corolla and I got it from my cousin and it was a little banged up so we got it for free and fixed it up and it drives great. It has 97,000 miles. My Q is about the speed and the odometer. My speed it 4 over what I go. Like 30 is 34 on the speed. so does the odometer match the actual miles I drive or will it be off also? Like when you put bigger tires on a car or truck. will that make any difference on the odometer. Always wondered but never asked.

The discrepancy may or may not affect the odometer reading. They are not usually fantastically accurate anyway. One way to find out is to drive the car on the Interstate and see how the reading compares with the distance between the mile markers. Most cars are off by some amount; 100-200 feet is fairly common.

You might also check the tire information placard, normally found in one of the door jambs or in the glove box, to find out what tire size your car originally came with. You may have the wrong tire size on at least one of your wheels. That will make a difference in the speedometer reading, and the mileage tracking of the odometer.

Most cars are designed to do just that. It is built in to help you avoid speeding tickets, but mostly to cover the manufacturer if there is an error that might result in a ticket or an unsafe speed. Correction generally will call for a speedometer shop. Note: even a change of tyres can make a difference.

I have checked mime out and the speedometer is off about 7% + or - but the odometer is dead on, which have been checked using the highway distance signs (good to a tenth of a mile per mile, and two different GPSs.) and OEM size tyres.

I agree with others…It’s a very reasonable question and concern if you care about maintenance and speeding tickets. Overall it at least errs on the side of safer operation. Before I’d conclude that there is indeed an error, make sure pressure is correct, you’re the only passenger and the tires are the recommended size before you conclude so.