Wheel size upgrade concern.
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Wheel size upgrade concern.
I have a 2012 FX4 SCREW. I recently upgraded from the factory 18" wheels to 20" XD Spys. Do I need to reprogram the computer? It seems to have changed the shift pattern a bit. I know this is to be expected. Just curious if reprogramming would help?
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The need for reprogramming isn't a function of the wheels themselves, but of the number of revolutions per mile of your tires. Look at the manufacturer's site for your old and new tires and get the revs/mile numbers. Divide the two and that will tell you how many percent off you are, which will help you determine if you should worry about reprogramming.
Most tuners also allow you to adjust tire sizes, if you are interested in going that way.
Most tuners also allow you to adjust tire sizes, if you are interested in going that way.
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Joined: Apr 2011
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The stock 18" tire is a 275/65/18 which is 32" diameter.
The stock 20" option comes with a 275/55/20 tire which is also about 32"
Go to the Tire Rack website and see what the diameter is of the tire your put on your
20" rims. If it's, say, 33", that's about 3% bigger, and you'll have a 3% speedo error.
That means about 2 mph at 70 mph.
Since you're probably got about that same error the other way, they'll cancel out.
That's the way I see it.
Tire/wheel combo with 20s may be heavier as there's more steel and less rubber.
In theory, this will make a small mpg difference, may not be enough to notice
Someone else probably has a better opinion on that.
The stock 20" option comes with a 275/55/20 tire which is also about 32"
Go to the Tire Rack website and see what the diameter is of the tire your put on your
20" rims. If it's, say, 33", that's about 3% bigger, and you'll have a 3% speedo error.
That means about 2 mph at 70 mph.
Since you're probably got about that same error the other way, they'll cancel out.
That's the way I see it.
Tire/wheel combo with 20s may be heavier as there's more steel and less rubber.
In theory, this will make a small mpg difference, may not be enough to notice
Someone else probably has a better opinion on that.
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Joined: Jun 2011
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Thanks for the info. I did see a bit of mileage decrease. Only a mile or two per gallon baaed on the dash readout. I have an edge evolution programmer but very seldom use it after it lost my factory program during upload and left me stranded, cost me $100 to re-flash my computer at the dealership.
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