Sport S (31") to Rubicon (33") wheels...do I NEED a programmer (Tazer Mini)

[MadMan81]

Excuse the ignorance if this was answered in another post, but all i saw were questions for larger 37" and 40" tire upgrades.

I just upgraded my stock OEM Sport S 31" wheels to Rubicon 33" wheels, and that's it! No lift, no spacers, nothing else! Is it suggested I buy a Tazer Mini to adjust my tire size, or will my car explode if i don't do it? Like can I get it later if I go up to a bigger tire size or upgrade my suspension?

Any advice or suggestions would be greatly appreciated. Thank you!

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[z0lt3c]

Going from the Sport 245/75/17 to the Rubicon 285/70/17 is a +3.8% difference. Thus, at 60 mph your speedometer will erroneously read 62 mph. That small of a change usually doesn't absolutely require a calibration.

The biggest benefit of the calibration is the readjustment of shift points, but your shift points probably aren't off by enough for concern, although your MPG readings will be inaccurate.

Maybe somebody else in Chicago can lend you a re-calibration tool for an hour.

 

[MadMan81]

Going from the Sport 245/75/17 to the Rubicon 285/70/17 is a +3.8% difference. Thus, at 60 mph your speedometer will erroneously read 62 mph. That small of a change usually doesn't absolutely require a calibration.

The biggest benefit of the calibration is the readjustment of shift points, but your shift points probably aren't off by enough for concern, although your MPG readings will be inaccurate.

Maybe somebody else in Chicago can lend you a re-calibration tool for an hour.

Thank you for that and it's what i think I already knew. but wanted to make sure there wasn't some other key reason i might need it. I might wait a bit before i get one.

Would my MPG read higher or lower?

 

[sarcasm]

https://tiresize.com/calculator/ will give you the mph difference. But it is about 2 mph based on what Waze indicated before and after the change. Really the difference is probably about the same as normal tire wear at the end of tread life.

 

[Bunchahoopla]

try to find the sizes approx. by height. So lets say one is 31", and you went to 33".

So 33"/31"=1.0645 these are always approximate. If you had a good distance each rolled per turn it could be more accurate.
The 1.06 is going to be what you need to multiply your tripmeter by to get actual miles closer.

Better yet, for easy math: actual distanced traveled and volume of fuel used when you refill. Use trip B for calculating miles and the pump for how much you put in. I am sounding old but I use to do this often growing up to figure MPG!

 

[Alabama Mud Machine]

You will need to reprogram the tire size, at minimum. But all the other features of the Tazer JL Mini are worth the money. I highly recommend it.

 

[Under-Pressure]

J scan app is another great way to change tire sizes for a fraction of the cost of other programmers. It's worth a look before you purchase something.

 

[PyrPatriot]

Recalibrating at the dealer from oem to 35s made a huge difference in mpg calculations, odometer, and gear shifting for me

 

[ksh67]

I just made this exact swap and it is exactly a 2 MPH difference. However, my Sport S Max tow was reading 1 MPH slower than actual based on few different inputs. GPS, HWY radar, clocking with other vehicle. SO in actuality when the odometer is at the speed limit it is really only 1 mph over. I won't be re-calibrating as I will be switching back to stock wheels and tires
]in the winter anyway.

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