Tire Size and Mileage Traveled

[SHOOT1SAM]

I've visited the website with the tire size calculator to determine how fast I am actually going on 265's as opposed to the OEM 245's. It works out to be about a 3. 88% difference-actually traveling 75 MPH at 72. 5 or so on the speedometer.



Here's my question-would this work out to actually travelling 3. 88% further than the odometer reads?



I'm trying to determine a more accurate average of fuel economy. The last tank of fuel and 408. 9 miles works out to 17. 4 mpg. IF the actual distance driven is 424. 8 (408. 9 + 3. 88%), then the average is 18. 07.

 

[big barney]

I am running 255's. My speedometer is off by 10 percent, but my odometer is off by 7. 5 percent. I muliply my mileage by 1. 075 to get the correct reading. I used a gps so I know it's accurate.

 

[Cooker]

Yes the odometer is off the same percentage as the speedometer. Be happy now that your MPG's are better than expected.



As mentioned above, I think the best way to get a accuracy reading from a speedo is a GPS. The mile makers along the highway are OK, but I have found them to be a bit off. If you use the mile markers, try it for quite a distance (at least 10 miles, the more the better). This will help offset the inaccuracies of the state employees who put the mile markers in.



Another thing to keep in mind is that the speedo may have not been 100% accurate from the factory.



-Ryan

 

[Blakers]

My truck has 265's and my speedometer still says I am going about 10% faster than I really am. Bigger tires will currect that for me. I usually use my gps for speed.



Blake

 

[Mundgyver]

Ive got stock tires and I still use my GPS. I find that the speedometer is off by about 1. 2 to the low side. 70 on the GPS says 68. 8 on the speedo. I work the fuel both ways and then average the two.

 

[klenger]

I checked my speedo with my GPS when I first got the truck. I expected the errors to be greater at higher speeds. I was wrong. I don't remember the numbers, but it was more accurate at 70 MPH than it was at 35. I think that the scale on the instrument is not linear.

 

[SHOOT1SAM]

Thanks for the replies, gang. I hadn't thought about checking things with a GPS, but will do so now. It's a small victory to learn that my mileage is higher than I had thought.