35s and MPG

[bisdak]

2014 RAM 1500 Sport. I just upgraded my tires to 35x12.5x22. For those who did the same, what did you have to do to recalibrate mpg? Thanks!

 

[crazykid1994]

Once you set your tire size in the computer it fixes your speedometer and that adjusts the mpg

 

[bisdak]

Once you set your tire size in the computer it fixes your speedometer and that adjusts the mpg

can you elaborate? did you mean bring it to dealer they can hook to some kind of calibrator or I can buy some device to recalibrate myself?

 

[Michael]

You can buy a tuner that will let you program new tire sizes. I don’t know if the dealer can do it. I’ve never been able to get a dealer to give me a straight answer about it. They might be able to get close.


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I know the voices in my head aren’t real, but man, do they ever come up with some great ideas.

 

[Fast69Mopar]

Any dealer that has the WiTech installed in the shop which is every dealer in North America can change the pinion factor to adjust for different tire sizes.

If a dealer says they cannot do it then go find yourself a new shop to do business with. It's just pure laziness if they say they cannot do it.


Make sure you get the exact tire "revolutions per mile" from the tire manufacturer so you can give it to the tech who is editing the pinion factor.

Not every 35" tire is 35 inches tall. If you put the wrong number in for the tire revolutions per mile speedometer and odometer will not be accurate not will your fuel economy.

If you cannot find the tire manufacturers specs for your exact tire you can do the math yourself.

Here is the formula I use...

RPM = 5280 / ((Tire Size /12*3.14159)

If you tire is exactly 35.0" tall:

RPM = 5280 / ((35 / 12 * 3.14159)
RPM = 5280 / ((2.916 * 3.14159)
RPM = 5280 / 9.160
RPM = 576

Or you can do this...

Tire Height * Pi (3.14159) /63,360

35 * 3.14159 / 63,360

Tire RPM = 576

 

[BOWERSFJ]

And we all said “We’ll never use this math crap after high school” ... Lol ... Nice job !!!


Sent from my iPhone using Tapatalk

 

[kurek]

Superchips makes an easy calibration tool. If your Ram is pre-2015 I think it can be software updated (for a fee) into a tuner, too if you want.

Edit: I just noticed this one is less expensive & should do the same trick minus the tuner part.