I have 07 F150 2wd with a rear axle ratio of 3.55. Changing from 18" to 20" wheel and tires combo. What will my rear axle ratio be at 20" wheels?

 

3.55...........

The ratio doesn't change.

 

20", 15", 24", whatever...has zero bearing on your overall effective gear ratio. You need to be concerned with overall tire diameter. That's what changes it. If you had a 35" tire, it wouldn't matter if it was on a 14" wheel or a 24" wheel, the ratio would remain the same.

 

Regardless of whether you have 29" or 40" tires on the truck, the GEAR RATIO is still going to be 3.55. Now, you CAN calculate what will effectively happen if you know the diameter of the original and new tires.

 

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