Tire Size
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Junior User
Joined: Jun 2005
Posts: 99
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From: Vancouver, WA
Tire Size
I purchased my 2000 Excursion LTD 7.3 about a year ago. It has 285/75 16 BF Goodrich AT KO's on it. So I am looking at the sicker inside the door the other day and see that stock tire size should be 265/75 16. My question... how much is this going to throw off my speedo and MPG calculations? How easy is it to recalibrate and how?
Thanks in advance for any help.... this forum has been a wealth of info for me already!!
Thanks in advance for any help.... this forum has been a wealth of info for me already!!
Senior User
Joined: Apr 2005
Posts: 430
Likes: 0
From: s.e. Michigan
First off, you do not really know if it was accurate with the 265's. I just pulled 265/70 x 17's off my new 250 and went 5 sizes bigger to 315/70 x 17's on the rear where the speedo works from and I have since run into some local radar displays by the schools that tell your speed and my speedo is right on NOW!!! That means I was overreading about 8% or so with stock tires. Forget complicated/expensive recalibration. Just do it in your head. Next time on the expressway, check your odometer as you pass a mile marker and then check it again as you pass a marker 10 miles down the road. If your odometer moved 9.8 miles, you are underreading by 2% which means when your speedo says 50 you are really doing 51. If it moved 10.3 miles then you are overreading by 3% and when your speedo says 50 you are really doing about 48.5. Easy! Anyone else notice their speedo overreads with stock tires? That actually will cause the owners to think they are getting better mileage than they are and it will also cheat on the warranty some.
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Junior User
Joined: Jun 2005
Posts: 99
Likes: 0
From: Vancouver, WA
Originally Posted by Danko
First off, you do not really know if it was accurate with the 265's. I just pulled 265/70 x 17's off my new 250 and went 5 sizes bigger to 315/70 x 17's on the rear where the speedo works from and I have since run into some local radar displays by the schools that tell your speed and my speedo is right on NOW!!! That means I was overreading about 8% or so with stock tires. Forget complicated/expensive recalibration. Just do it in your head. Next time on the expressway, check your odometer as you pass a mile marker and then check it again as you pass a marker 10 miles down the road. If your odometer moved 9.8 miles, you are underreading by 2% which means when your speedo says 50 you are really doing 51. If it moved 10.3 miles then you are overreading by 3% and when your speedo says 50 you are really doing about 48.5. Easy! Anyone else notice their speedo overreads with stock tires? That actually will cause the owners to think they are getting better mileage than they are and it will also cheat on the warranty some.
Elder User
Joined: Sep 2004
Posts: 824
Likes: 0
From: Helotes, Texas
The tire size change puts you about 3.7% off stock which is not much (at 50mph on the speedo, actual speed is 51.85mph). Check out this site for size comparisons. http://www.powerdog.com/tiresize.cgi
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