GPS error due to 37" tires?

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tec548

tec548

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According to the dealership I was at, they cannot re-calibrate the speedo for tire size. I find this hard to believe, but that is what they told me. However, my NAV is now working with the 37's. I don't know what they did but it's working. They even told me that they could not fix it before it was picked up.
 

Huck

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lets see they changed nothing. Probably flashed the Nav system, and yet still on 37's. sounds like the nav system has nothing to do with tire size.

If peole are having the same issue with 35's.
 

Nick@Apollo-Optics

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lets see they changed nothing. Probably flashed the Nav system, and yet still on 37's. sounds like the nav system has nothing to do with tire size.

If peole are having the same issue with 35's.

I've never had the issue of the nav system "lagging behind" but I have had the issue a couple times where the truck thinks that I'm driving through a row of buildings instead of on a street and corrects itself after a few miles. All of this has been on factory tires.
 

Jordan@Apollo-Optics

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Buddy with a regular 5.0 F150 lifted with 35's on it had his speedo recalibrated up in College Station. Cost him $80 bucks for the service.
 

SlimChaChi

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I had the nav issues on my FX4 when i put 35s on it. Had to disconnect the negative battery cable for about 30 minutes and then reconnect. Nav went back to normal. Speedo I recalibrated with an SCT Livewire.
 

SlimChaChi

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my guess is the system is somehow programmed to use the number of revolutions per mile on the stock tires to calculate distance traveled. can't be 100% certain...just a guess though...
 

Cleave

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How would revs in any way shape or form effect GPS which uses time and triangulation from satellites? Must be missing something here.

The GPS system uses a lot of in vehicle sensors to simulate GPS tracking in case communication to the GPS satellites is lost, vehicle speed, the different roll rate sensors, the steering wheel angle sensor, and many others, most likely what is happening with the 37" tires is that all the vehicle sensors are saying you're going X miles per hour, while the GPS satellites are saying you're going 3 miles per hour faster than the sensors say, modern vehicles are programmed to ignore the one input that doesn't match up to all the others to try to prevent minor failures from putting you on the side of the road for 3+ hours, the GPS system thinks all the vehicle sensors couldn't be wrong all at the same time, so the GPS satellites must be wrong, so it ignores the input from them and tries to keep track of your vehicle with the in vehicle sensors alone, which is why the GPS is falling behind, nothing is wrong with your GPS, the GPS just thinks there is, usually ford has programs for +1 and +2 tire sizes, a dealership should be able to reprogram your control modules for the larger tires

That is how it could
 

Orionkhan

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That is how it could

Yeah. My nav went goofy immediately after switching to 37's. Did the disconnect trick and it fixed the problem. I think that disconnecting the negative battery cable must make the nav recalibrate itself to the sensors that it uses in between gps pings. As others have noted, this is a Ford nav problem with other vehicles and tire size changes also. The negative battery cable disconnect trick seems to work more consistently than any other fix.
 
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