99STEEDAGT

hey. just wondering if anyone can help me out with this. i just got 18x9 bullitt wheels for the front with 265's 35 18's and i have 18x10 deep dish rims with 285 35 18's. do you have to reflash the computer so the tach., speedometer, and the mileage stay accurate? thanks!

Tac2cul

you have to either get a tuner to correct the speedo or a speedo correction device(i dont recall the names of any right now)

99STEEDAGT

yeah i wasnt sure if i need a recalibration. thanks! i looked into it, and the device your referring too is a SpeedCal ( something or other) its used for 96-98 GT's with automatics, and 99 to 04 GT's with standard trannys.. i have a 99 automatic... what do i do?? SCT tuner?

gt96stang

Since you have an auto, the SpeedCal will be useless to you.. The only way to fix for a tire change is to buy a tuner.

99STEEDAGT

thanx!! i thought so.. but someone also told me that auto's didn't need to calibrated.. thanks again!

Miliock

those tire sizes make only a fraction of an inch change in over tire diameter....you shouldnt need to change anything IMO. I run the same tire up front and 295/30/18s in the rear and it makes less than a 1 mph error at 65 mph on the speedo

newb2000GT

Check ou tthe tire size calculator in the stickies. Enter your tire sizes and it will tell you how far off your speedo will be...

rayj1019

yea you have to change it ...andd u have to redo some of the calculations in your computer cause the car has anti lock brakes so the car isnt going to stop right

sc94gt

You don't have to recaliberate anything.
285/35/18's just about equal the diameter of 245/45/17's.
It would be a wasted effort.

Miliock

that's what i was saying