Lager tires C6 corvette 285/35zr19 to 345/30zr19 what to change

[Rayzzz]

Using V2 what do I need to change to get the speedo and trans shifts correct for my 2005 C6 Corvette A4 auto that I installed a rear Z06 widebody and Z06 rims. I changed the rear tires from 285/35zr19 (26.5 tall) to 345/30zr19 (27.17 tall) and the fronts from 245/40zr18 (25.6 tall) to 255/40zr18 (25.98 tall). Tires went on yesterday and the roads are full of salt and snow so I figured I could work on program so when the roads are good I can have a tune in and ready to roll.
THANKS RAYZZZ

[Taz]

Hello Rayzzz,

In your TCM tune open – Transmission Calibration – Speedo – Parameters. Click on the Speedo Calculator tab. Input your new tire diameter – which should update the revolutions per mile (H0136) value. Click apply.

Click on the Shift Point Correction tab. Enter your original tire diameter – then confirm the values of your new tire diameter and diff ratio are correct. The “Adjust by:” box should now be showing a percent correction factor (probably about 2.5 %). Confirm all boxes below are check marked. Click apply – only click once !

Save the modified TCM tune to a new file name.


Regards,
Taz