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Discussion Starter · #1 ·
I was just wondering....If I put some 20's on my truck and which that will prob put me with a larger tire...does it effect your speedometer much? I've heard it does, but I never knew how much. Can I get some opinions on this. Thx... :gmfs: Sorry, meant to put this in the Exterior forum instead of this one.
 

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I'm back!
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I think it changes it by a few MPH. I have oversized All terrains and it only changes my speedometer by 2-3. Since your truck is a 2k a hypertech programmer would be able to change it to the right tire size that you have.
 

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Drive It Like Ya Stole It
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6,656 Posts
Its not a fixed MPH but a percent you will be off. Just take the circumference of your old tire vs your new tire and see the difference. That is the percent you speedo will be off. It wont be to much. For instance, going from stock to a 35" tire my speedo was under 10% off.
 

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Line-X of San Antonio
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5,237 Posts
im running 275/45/20s and mine is barely off if it is at all.. they have those speed trap things here that tell you youre speed, and im always doing what it says.
 
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