Larger tire- speedometer reprogramming

[WtrskiAdic]

I'm sure this issue has been hashed and rehashed to death but I could find it so I going to post it again is there anyway to adjust/ reprogram the the speedometer after increasing tire size from 31x10.5/15 to 285-75/16 other than buy a aftermarket programmer

 

[3.0ranger1227]

Either have to use a programmer, get the ECU reflashed(the dealer can do this IIRC), or change the gearing to correct it.

 

[gw33gp]

I looked into this thoroughly when I switched to 33" tires and 4.56 gears. The dealer wanted too much money to calibrate the speedometer and was a one shot deal. My programmer would not recalibrate the speedometer and no one could reprogram it. I was not willing to buy a new one.

I found the least expensive way to recalibrate the speedometer on a 2002 is with a Recalibrator from Dakota Digital. I searched hard and found one for $75. They are normally more than that but you can usually find a deal on them. The recalibration process seems complicated but once you understand, it not that bad. The nice thing is you can change the calibration over and over, if needed. I switch back and forth between 33" and 31" tires so it is ideal for me.

It is not programmed by tires size and gear ratio. You will need a GPS or a known distance to get it set right. With a GPS you can you can preprogram it if you know how much the speedometer is off or you can do it while you are driving.

It does require hard wiring into the wire that goes to the speedometer as well as for a source to power to it. The faint at heart when it comes to wiring should not consider this route unless you have someone that can do it.

 

[adsm08]

Having the dealer do it has another draw back that was not brought up.

When correcting the speedo with the factory scanner we do it by telling the computer the gear ratio and tire size. Since Ford doesn't expect people to bring modified vehicles to the dealership we are limited to the factory available options for choices, so I can't tell it that you have 5.13 gears or 35" tires.