West Coast

If my truck cam with stock tires size of 265's. And I now have 315's. If I drive a mile on the speedo how far would I have driven with the 315 tires? I know if I check my mileage it will be off due to the larger tire size? Thanks....

Dave

kevellis32

On my truck it was about a 20% a difference in speed. Meaning if i was going 10 on my spedo i was doin 12. So i just figure that my odometer is 20% off too. Be very careful with the speed, it got me nailed about 2 days after i put on the tires and wasn't thinking...Got pulled over doin something in the 90's with the spedo at about 75, luckily the cop understood and only gave me a warning.

dsl4me

Find someone with a GPS and have them go for a ride with you. That's how I narrowed down my difference to 7%. Went from 245s to 285s.

waldersha

You can also go to almost any tire site and figure out the difference in size of tires to get the difference in your speedo and odometer. I used 1010tires.com and came up with 9.349% difference between 265-75-16 and 315-75-16's. So if you are showing 54 on the speedometer, you are actually going 60. That doesn't take into account if you are running the same rims on this bigger tire though.

Hope this helps.

West Coast

So if my truck is getting 19 MPG. I would add 9% to get a accurate MPG with the 315's?

Dave

waldersha

Correct, or more accurately, you would add 9% to whatever miles you have between fillups. So if the trip odo reads 100 miles, you have actually gone 109 miles. Then use that to figure your MPG. You can also check this on a trip down the interstate. Just use the mile markers, run for 10 miles by them and see how much you are off. Should be about .9 miles.