Changing wheels size

[Lbj]

Hi everyone I have a question I going to put on new wheels and at the moment I have a stock 18 inch wheels I picked up some OEM 19 inch wheels & with the automatic transmission do I need to program for the bigger wheels and tires will the odometer be off much thank for any help

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[m3incorp]

It depends on how far off the overall wheel/tire diameters are from the factory wheels. For example, I went from the stock 18" 255 wheels/tires to 20" 305 wheels/tires and my speedometer was reading 2 mph slower than actual speed. Roush tech reprogrammed during a calibration update and now it reads 5 mph slower than actual speed lol.

Hi everyone I have a question I going to put on new wheels and at the moment I have a stock 18 inch wheels I picked up some OEM 19 inch wheels & with the automatic transmission do I need to program for the bigger wheels and tires will the odometer be off much thank for any help

 

[JK XLR8]

It depends on how far off the overall wheel/tire diameters are from the factory wheels. For example, I went from the stock 18" 255 wheels/tires to 20" 305 wheels/tires and my speedometer was reading 2 mph slower than actual speed. Roush tech reprogrammed during a calibration update and now it reads 5 mph slower than actual speed lol.

305/30/20s in the rear would have been a little closer to the stock diameter. The 305/35/20s are over an inch taller...

 

[EFI]

do I need to program for the bigger wheels and tires will the odometer be off much thank for any help

No you don't need to reprogram anything unless you go with overall tire sizes that are much different than OEM. And how far off your speedo will be depends on the overall diameter of the new tires.

 

[NightmareMoon]

Its not the wheel, its the diameter of the tire.

Usually going from 19s to 19s or 20s, you'll go with tires with shorter sidewalls to keep the diameters similar.

 

[m3incorp]

You are correct and I did know that going in. I wanted the little higher sidewalls and wanted to fill the wheel wells.

305/30/20s in the rear would have been a little closer to the stock diameter. The 305/35/20s are over an inch taller...

 

[JK XLR8]

You are correct and I did know that going in. I wanted the little higher sidewalls and wanted to fill the wheel wells.

Gotcha, I went back and forth between the 35s and 30s in rear...tough decision! I like the way both look, but the 35s do fill it in a little better.

 

[m3incorp]

I've got a ForScan, so one of these days I will take time to set the speedometer. The interesting thing is I saw what the tech entered and it was correct for the 305 change but threw my speedometer off more. I checked it against my Uniden R7 GPS and the phone.

Gotcha, I went back and forth between the 35s and 30s in rear...tough decision! I like the way both look, but the 35s do fill it in a little better.

 

[JK XLR8]

Understood......when the dealer installed my blower, I asked about tire sizing and speedo, they basically said try to keep it as close to factory diameter which I did. I am not sure if its off, I will check on the ride home and update!

 

[rxryanm]

Fairly confident you can update size with Forscan.

 

[Lbj]

Ok the stock 18 inch tires (235 50 18) and
The 19 inch are (255 40 19)front (275 40 19 ) rear

 

[m3incorp]

That is the Ecoboost size, correct?

You only have to compare the rear sizes for the speedometer.
You are at 27.3 vs 27.7" in total height. That is so close that you may not need to make any Speedometer calibrations.

Ok the stock 18 inch tires (235 50 18) and
The 19 inch are (255 40 19)front (275 40 19 ) rear

 

[Lbj]

They are off a 2020 GT
9 and 9.5 wheels

 

[m3incorp]

They will fit the EcoBoost GT or 5.0 GT with no problem and with the same results. You just have to compare them to the size that came on your car

They are off a 2020 GT

 

[Lbj]

Ok thanks

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