Oddometer/Speedometer vs 20" tires
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From: CC
Oddometer/Speedometer vs 20" tires
All,
I had a question regarding the Oddometer/Speedometer and the 20" tires. Will putting smaller tires on the F150 increase the reading on the Oddometer? If so, do I have to take it into the dealership to adjust?
Thanks
Ed
I had a question regarding the Oddometer/Speedometer and the 20" tires. Will putting smaller tires on the F150 increase the reading on the Oddometer? If so, do I have to take it into the dealership to adjust?
Thanks
Ed
Senior User
Joined: Oct 2007
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From: Burleson, TX
Originally Posted by Twinsdad98
no, it's done through sensors so you needn't worry. I run stock 18s in winter and 20s summer. Speedo has always been correct
Fleet Mechanic
Joined: Nov 2004
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From: Pittsburgh, PA
Originally Posted by Twinsdad98
no, it's done through sensors so you needn't worry. I run stock 18s in winter and 20s summer. Speedo has always been correct
305/50/20 = 32.01 inches
275/65/18 = 32.07 inches
Fleet Mechanic
Joined: Nov 2004
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From: Pittsburgh, PA
Originally Posted by edmundo7
All,
I had a question regarding the Oddometer/Speedometer and the 20" tires. Will putting smaller tires on the F150 increase the reading on the Oddometer? If so, do I have to take it into the dealership to adjust?
Thanks
Ed
I had a question regarding the Oddometer/Speedometer and the 20" tires. Will putting smaller tires on the F150 increase the reading on the Oddometer? If so, do I have to take it into the dealership to adjust?
Thanks
Ed
also, this site helps calculate the tire difference: http://www.miata.net/garage/tirecalc.html
Fleet Mechanic
Joined: Nov 2004
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From: Pittsburgh, PA
you should be fine then if you stick with the stock sizes. The stock 20's come with 275/55/20 tires which are 31.9 inches tall. The stock 18" 4x4 size tire is 275/65/18 which is 32 inches tall. You won't have to do any kind of adjustment/calibration.
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Posting Guru
Joined: Jul 2005
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From: Denver, Co
You might want to do a few searches as well, this comes up pretty regularly....kind of like this one from last week....
https://www.ford-trucks.com/forums/7...ire+gear+ratio
https://www.ford-trucks.com/forums/7...ire+gear+ratio
Elder User
Joined: Dec 2003
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From: Austin TX
And it's not that you HAVE to recalibrate. You can just leave it and remember that your speed and mileage will be 'off.' It's just a measurement, etc. ... no real bearing on the functionality of the truck, etc. 
Posting Guru
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From: Denver, Co
That's not entirely true. The series of computers that control your drivetrain rely on these readings for many things--not just to display speed & calculate miles traveled. Tire swaps can lead to automatic transmissions not shifting correctly & your ABS not operating optimally.
The larger the change, the larger the impact.
The larger the change, the larger the impact.