Gears, Tire Sizes, and speed re-calculation

[JTStreet]

This is all related to a 2001 Cobra.

Stock Tire Size - 245/45/17
Stock Gearing - 3.27


My Tire Size - 275/35/18
My Gearing - 4.30

Based upon this information, how should I re-calibrate my speedo? It is currently tuned with an X3, so I assume it can be accomplished through this. I have found calculators that show information for source/target tire size, but not throwing aftermarket gear ratios into the mix.

I assume with the X3, I do not need a different speedo gear, and this can be accomplished through the tune, correct?

 

[01yellercobra]

The new tires should be the same overall diameter as stock. You should just have to select 4.30s under the options menu.

 

[JTStreet]

The new tires should be the same overall diameter as stock. You should just have to select 4.30s under the options menu.

Is this done from the handheld options or the tuning software itself?

 

[01yellercobra]

You can do it from the hand held as long as your tuner set up the options.