Nothing enhances the looks and improves the performance of a 4x4 faster than new meats. Bigger tires provide more ground clearance, betting climbing capabilities and a smoother ride off-road while turning heads on the street. There is a dark side however, and that is the effective loss of power.
Tires size is one of the numbers needed to provide a final drive ratio (FDR), changing a tire size is changing a gear… and going bigger on the tires adversely affects the FRD. That's the bad news. The good news is it can be fixed by changing the ring and pinion (axle) gears. You can click HERE for Best Off Roads Ratio, Speed and RPM Calculator or Below is a chart to help you choose the right gears for you.
How it works:
The column on the left is labeled Tire Diameter. Tires vary a little so use the published size located on the sidewall of your tire to make an initial assessment.
The row in red, labeled “Ratio” indicates the ring and pinion (axle) ratio. You can find the ratio on a tab mounted to the differential cover or by looking it up online ( https://www.mopar.com/jeep/en-us/sign-in.html )
Step 1
Select your current ratio and tire diameter. The intersection between the column and row indicates the rpm at 60 mph in a transmission gear that is 1:1. Write down the RPM (example: 3.73 Ratio gears and 33 inch tires intersect at 2469 (rpm))
Step 2
Select you're the tire diameter you are going to from the options in the left … the new badass tire size. (Example 37”)
Step 3
Follow the column to the right and find the nearest RPM to your original RPM… the number you wrote down.
Step 4
At the top of the column is the new ratio. This is the ring and pinion ratio you should look for to achieve your previous gearing.
Note: If you want lower gears, select a ratio with a higher numeric value (example: 4.56
gears are a lower ratio than 3.73)
Not to hard was it… Reach out to BestOff-Road.com if you have any questions… we love talking gears and helping you build your dream ride.
