When you change your tire size you need to make sure you have the right gearing to get optimal fuel economy and power. A good way to calculate this is to multiply 0.12 by your 4wd's tire diameter (Example: 0.12 X 38" = 4.56).

Here is an easy to read chart for you to get a good estimation on the best gearing for your 4wd. The three distinct colors below can help you decide what is the right gearing for you...

  • Green = Best MPG, this is what you would want to get for the best fuel economy and highway cruising.
  • Brown = Best Overall, this is good mix of power/MPG and considered best for daily driving.
  • Orange = Best Power, this will give you the best performance for towing power, but at the cost MPG.

These calculations are assuming you are at 100 KPH with a gear ratio of 1:1 (3rd gear in an automatic and 4th gear in a manual) If you drive in overdrive your RPMs will be slightly lower.

Tyre Size
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Gear ratio chart


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