Speedo recalibration
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New User
Joined: Sep 2014
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Speedo recalibration
Switching from 20 inch wheels to 18 inch on a new Superduty. I know, I know, but I like the looks of 8teens better. So my question is, does that screw with the speedo? Does it need to be recalibrated, or am I overthinking things?
Junior User
Joined: Aug 2012
Posts: 56
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If the diameter of the tires on the new rims is different, yes you will have to change it.
The trans shift points will change also.
On my old truck, I changed the calibration using my tuner.
I am not sure if this is the case with your truck.
LA
The trans shift points will change also.
On my old truck, I changed the calibration using my tuner.
I am not sure if this is the case with your truck.
LA
Laughing Gas
Joined: May 2007
Posts: 812
Likes: 3
From: Mad River Valley
Dealer can reprogram to a size that is in the Ford system that was available for your model truck. I went from 18's to factory 20's and the wheel diameter is definitely bigger in my case. Will be the opposite for you.
Fleet Mechanic
Joined: Jul 2013
Posts: 1,330
Likes: 65
From: 'Pitlock, Maine
I have an F250 with 17 inch wheels on it now....I have a set of 18inch wheels with traction treads to put on it for the winter for plowing.Will this be possible on my truck.... 2007 F250 XL Thanks and sorry for the hijack.
Senior User
Joined: Dec 2005
Posts: 283
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From: Vero Beach, FL
Wheel diameter makes no difference with regard to speedo calibration. TIRE diameter makes a difference. If your tire diameter stays roughly the same, you are good.
Best advice is to make the swap, then run your speedo against a GPS to see how much your indicated speed varies from actual. If it's significant, you can either change it with a tuner (expensive option if that's all your going to do), or get the dealership to do it (should only cost you an hour of labor).
If it changes enough to warrant a speedo change, you might consider whether you've affected your final drive ratio enough to need to adjust shift points (assuming you're an auto).
Best advice is to make the swap, then run your speedo against a GPS to see how much your indicated speed varies from actual. If it's significant, you can either change it with a tuner (expensive option if that's all your going to do), or get the dealership to do it (should only cost you an hour of labor).
If it changes enough to warrant a speedo change, you might consider whether you've affected your final drive ratio enough to need to adjust shift points (assuming you're an auto).
Junior User
Joined: Aug 2012
Posts: 56
Likes: 0
Wheel diameter makes no difference with regard to speedo calibration. TIRE diameter makes a difference. If your tire diameter stays roughly the same, you are good.
Best advice is to make the swap, then run your speedo against a GPS to see how much your indicated speed varies from actual. If it's significant, you can either change it with a tuner (expensive option if that's all your going to do), or get the dealership to do it (should only cost you an hour of labor).
If it changes enough to warrant a speedo change, you might consider whether you've affected your final drive ratio enough to need to adjust shift points (assuming you're an auto).
Best advice is to make the swap, then run your speedo against a GPS to see how much your indicated speed varies from actual. If it's significant, you can either change it with a tuner (expensive option if that's all your going to do), or get the dealership to do it (should only cost you an hour of labor).
If it changes enough to warrant a speedo change, you might consider whether you've affected your final drive ratio enough to need to adjust shift points (assuming you're an auto).
It started shifting as it should.
LA
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