Ford 1 ton tires/rims

[Trashy]

I have a HD edition, that has factory 275/65 R20. I have been thinking of taking off the 20's and go to an 17 or an 18. To have more choice's of tires, and less money.
The spare is a 275/70 R18 and when mounted, there's an extra 1/2 inch of clearance in my wheel well. Which isn't a big deal for me....
So if i went to 18's, how much would my speedo be off being 1/2" smaller tire and are 18's very popular?

 

[sirkdev]

18's will ride better with more side wall, they are cheaper also. They don't look as good IMO. To figure out difference in speedo use a gps to compare to dash or measure overall tire diameter also available from manufacturers websites and compare the two and figure out a percentage of difference. Likely you wont notice very much at all because that truck came with both 18's and 20's from the factory and I doubt they are programmed different from the factory for speedo cal. But you never know.... GPS is the easiest.

 

[adamg]

Tire Size Calculator
Click on the Tire Size Comparison tab.

 

[Clode]

they can adjust tire size in the ecm so the speedo reads correct

 

[007sevens]

they can adjust tire size in the ecm so the speedo reads correct

fuel milage calculators are more accurate as well.