Tire Size (not what you think)

[Mr_TT-89]

Hi guys,

so ive changed my tires over to a 255/75/17 and ive realized at 100km im doing 110 and at 70 im doing 80km (figured it out after driving past a speed camera and using a GPS app to see speed), now ive got a OBD2 module and Jscan, apparently you can change the tyre size on the computer to help adjust the speedo to proper speed display just no idea how to do such a thing, just wondering if anyone has successfully done that before and if they could give me a run down on what needs to be done.

[Gojeep]

I did mine last week but used DiagFCA software. Just had to type in the circumference and that was it. Used it on the KK as well.

[Mr_TT-89]

All good guys, was able to figure it out very self explanatory from youtube, ended up going up a small bit so when i do 50 in the car im doing 48 which is better for me now! anyone has any issues or wants to know how to do it on jscan hit me up ill send you the link VERY EASY to do!...