5th generation Ram Bighorn going to 275x60-20 from 275x55-20 tire size

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John Meisner

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2019
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has any one changes their tire size on the 2019/2020/2021 Ram Bighorn tire size to 275x60-20 from 275x55-20. i know that they will fit the truck but will i have problems / issues going to this new tire size with the electronics, namely, do i need to re-calibrate the computer (what-ever) so that i do not have any error / functioning messages on the dash ?
 
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Mehgyver

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I went up from the 55's to a larger tire, other than your speedo being wrong you wont see any issues. Maybe the mpg estimates might be slightly off? As far as speedo goes, you can either buy a reprogrammer and update the computer with new tire size (not updating doesnt throw errors or anything, your computer doesnt know you increased the tire size unless you tell it) or you can just do the math in your head, you probably wont be more than a 1.5 to 2.5 mph off depending on speed. You can take a look:

https://tiresize.com/speedometer-calibration/

for example with the tire change you mentioned when your speedo shows 45mph you're going 46.5mph, when your speedo shows 65mph you're actually going 67.2mph. So the delta changes as your speed increases as youd expect.
 
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John Meisner

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Thank you "Mehgyver" for your response. I am going to put on 275x60-20 Michelin Defender LTX M/S on Tuesday as i like a quite and smooth ride. I am going to Montana to visit 2 nephews on Sunday so i wanted to make sure that i would have no problems. i am in Michigan.
 
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