Tire size and speedometer issues

[RYUICHI TANAKA]

Change tire size to 295/30R26
I changed it, but the speedometer is not normal.
But it was fine when I changed it before.
what should i do?
Please tell me how to do it.
By the way, the device has been updated to the latest.

[06MonteSS]

Do NOT go by the sidewall sizing.. you need to actually measure your tire height, from the ground to the top of the tire, and you'd use that inches amount to set the tire height/diameter...

so then you'd go to Tune Vehicle - Advanced Mode, and select the ECM tune to install.. then choose to Modify the tune... then go to Speedo correction menu, and then adjust the tire height/diameter setting.. then exit back out, and then install/apply the tune..

that will re-install the tune with your tire size adjustment in it.

as long as it's within 0-1 mph compared to a GPS, you're fine and good to go.

[RYUICHI TANAKA]

hello. MonteSS, I understand.
I will try!
Thank you for your thoughtful answer.
you are a very good engineer