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

 

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

 

That is not correct. If you change the overall height of the wheel and tire, it has to be recalibrated in the computer to be correct. That is one of the reasons some people buy a tuner. The size of the wheel can be changed and with a different tire, the overall height might be the same and then you would not need to recalibrate. Some people go to the dealer to get it changed, but if they charge for it, you would be better off getting a programmer.

 

you don't notice a speedo difference because your 20's have almost the same diameter as the stock 18's.

305/50/20 = 32.01 inches
275/65/18 = 32.07 inches

 

you need to tell us what size you have now and what size do you plan on changing to?

also, this site helps calculate the tire difference: http://www.miata.net/garage/tirecalc.html

 

Sure thing SteveVFX4,

It's a 08, 20"
I would take it down to 18"

 

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.

 

Thanks All!!!!

 

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

 

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.

 

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.