Wheel / speedo re-calibration

[moates88]

I just swapped out my stock 18's to 20in wheels, I would assume I have to recalibrate my speedo to make up the difference in wheel size... How would I go about that?

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[Zemedici]

Good question, I asked Lund and apparently with the 15s there's not a specific way in the PCM calibration to do it like with older models. I can't use the IDS at work (Ford) either because it's not a factory wheel size.

So in for results :cheers:

 

[Khyber]

i know on a cjpp video they said to go to the dealer.

difference isn't worth the price imo...check out one of the speed to tire ratio calculator thingys to tell you how much it should be off. it won't be large. then just compensate for the difference

 

[moates88]

God forbid it's easy lol
I'm ocd so I'll probably ending up going to the dealer unless it's some ridiculous price. If it's only off by a few mph's then I guess I can live with it.
Thanks for your input guys

 

[Need4SpeedMotors]

It shouldnt be off nore then 2 to 3 mp. I knownyou can go to the dealership and they can recalibrate it the charge around here is 1 hours worth of labor so whatever that is.

 

[moates88]

It shouldnt be off nore then 2 to 3 mp. I knownyou can go to the dealership and they can recalibrate it the charge around here is 1 hours worth of labor so whatever that is.

In that case I wouldn't even waste the money lol I have lowering springs to install haha
Btw my wheels and tires came in and are on the car. My god it looks badass. Thanks for all the help too bro

 

[2Cool]

Using a tuner you can tweak with the gear ratio to get it to work.

However; you may not need to do anything if the overall diameter of your wheels remains the same. Check with any of the online tire comparison tools, if you went with the right sidewall ratio you should be about the same overall circumference.

http://tire-size-conversion.com/tire-size-comparison/

http://www.discounttire.com/dtcs/infoTireMath.do

 

[magnetic5oh]

I'm assuming the car takes the speed reading from the front wheels but can anyone confirm this? My fronts are overall shorter then the rears so I just want to know which wheels to adjust my speed by.

 

[MSMStannyl]

Using a tuner you can tweak with the gear ratio to get it to work.

However; you may not need to do anything if the overall diameter of your wheels remains the same. Check with any of the online tire comparison tools, if you went with the right sidewall ratio you should be about the same overall circumference.

http://tire-size-conversion.com/tire-size-comparison/

http://www.discounttire.com/dtcs/infoTireMath.do

This ^. As long as you're keeping the same overall diameter (with the wheels + tires), you will be fine. Technically that's how you're "supposed" to upgrade wheel sizes.

The base GT has 18" wheels. The PP has 19" wheels. I have the 20" wheel option on mine. As the wheel size goes up, tire sidewall goes down. All 3 of the above wheel/tire packages should have the same overall diameter. Obviously if you didn't stick to this "rule" than yes, your speedo will be off and will need to be recalibrated.

 

[SC_Sport_Pilot]

Going from the 19" Performance Pack wheels and tires to the monsters now
on the car my speed is off by 2.4 mph as measured with GPS. I am not
worrying about it.

 

[Need4SpeedMotors]

In that case I wouldn't even waste the money lol I have lowering springs to install haha
Btw my wheels and tires came in and are on the car. My god it looks badass. Thanks for all the help too bro

YES ! !!!

images brotha lol

 

[Finally]

Using a tuner you can tweak with the gear ratio to get it to work.

However; you may not need to do anything if the overall diameter of your wheels remains the same. Check with any of the online tire comparison tools, if you went with the right sidewall ratio you should be about the same overall circumference.

http://tire-size-conversion.com/tire-size-comparison/

http://www.discounttire.com/dtcs/infoTireMath.do

Thanks for the links!

 

[ElAviator72]

I'm kind of wondering about my factory calibration...I took my car on a road trip for the first time last week and set the cruise on the interstate. I noticed that the cruise control speed was about 2 MPH lower than the speedo said I was doing...

 

[GTP]

God forbid it's easy lol
I'm ocd so I'll probably ending up going to the dealer unless it's some ridiculous price. If it's only off by a few mph's then I guess I can live with it.
Thanks for your input guys

I am willing to bet $10 that there is a federal law that requires it not to be easy. addle:

If I were to run summer/winter setups that were much different in tire diameter, I would consider splitting the difference between the two. Each would be "off" by only half the worst case, but also, the total miles odometer would be overall more accurate. Since half the year it overestimates and the other half it underestimates. I would say a good rule of thumb is to not worry if it is within 3% (2mph at 60).

I think it goes without saying that the speedo runs off the front wheel (think lack of wheel spin), so that is the tire that needs to closely match the OEM diameter.

www.wheel-size.com

 

[plc268]

I'm kind of wondering about my factory calibration...I took my car on a road trip for the first time last week and set the cruise on the interstate. I noticed that the cruise control speed was about 2 MPH lower than the speedo said I was doing...

No, it's not that. It's because you're looking at the speedo off angle. For some reason, ford decided not to angle the speedometer toward the driver. If you move your head so that you're dead center in front of the speedometer, it'll likely be "accurate."

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