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Speedometer re-calibration for larger tires

10640 Views 9 Replies 7 Participants Last post by  Tde0411
Hi All,

I hopefully will be getting a Rebel very soon and am just doing pre purchase research. I have searched but haven't found anything regarding Speedometer re-calibration for larger tires. For those of you that have upsized you tires how have you re-calibrated? I'm hoping to go 35ish.

Thanks in advance

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I just use the speedometer app on my phone. I am about 5 mph off after putting 35's on
Joe's got it pretty close. The exact difference with going from a 33 to a 35" tire is you are traveling 6% faster than your speedometer reads. If it reads 100, your actual is 106. 50 => 53.

Your economy will also be off. It will read 6% low on the computer. If it shows 25mpg you're really getting 26.5mpg.
I would like to be able to recalibrate for 35" tires as well. I think the dealership can only go up to 33" tires because that is as big of stock tire they get, but I'm trying to learn more about Hypertech's Speedometer calibrator. On another forum Hypertech says that the calibrator doesn't involve the PCM so I want to talk to the dealer and see if it would cause any warranty issues.
You can also buy a calibrator tool like this. Not sure it'd be worth it to me. But I would think 4 wheeler and/or truck tire shops might have one.

Hypertech Speedometer Calibrator - FREE SHIPPING
Talked to the dealer near me and they said using the Hypertech calibrator won't cause any problems with warranty.
I would want everything recalibrated as well but wish there was a cheaper option.
I bought the Trinity diablo sport tuner package and I can adjust tire height for the 35's. Works great. I would suggest dealer recalibrate for you. They should do that for you at no charge. Just plug up to your OBD and make the switch.
I thought you had to do a pcm change to use a tuner on the Rams?
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