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-   -   Determining Speedometer Error Due To Tire Size Change (http://www.ramforumz.com/showthread.php?t=89204)

MADDOG 08-09-2011 05:23 PM

Determining Speedometer Error Due To Tire Size Change
 
When you change tire sizes, you will experience some speedometer error. Indicated speed may not be your actual speed.

So, if you are curious about how big of a change you will experience, go here:

Speedometer Error Calculator

Then, plug in your stock tire size (or your current tire size if you have adjusted your PCM for this using a programmer) and the new tire size to see what the change will be.

Stangshcky12 08-09-2011 06:00 PM

http://www.1010tires.com/tiresizecalculator.asp
That is the tool I like to use as well. It has other handy calculations along with your percent difference of tire sizes

Dancianne 09-14-2011 08:04 PM

Already swapped tires?
 
For those of you who have already swapped tire sizes before using one these handy calculation tools, get a gps unit, most will tell you exactly what your true speed is.

pall2509 09-25-2011 11:12 AM

good stuff, i also use my garmin!

Boubou 10-13-2011 10:56 AM

is there no way to calibrate the tire change in the computer?
what are the ramifications of going from 20 to 17?

SeattlePete 10-13-2011 11:43 AM

A programmer (Predator/Trinity) can be used to change the tire size in the PCM.

As far as going from 20" to 17"- lots of factors to consider, but the main ones are overall tire diameter, rim/tire weight, and rim offset (aftermarket rims). You can go from a stock 20 to a 17, keeping the overall diameter the same, and you'll have no problems.

DrumMedic 05-02-2012 02:42 PM

Quote:

Originally Posted by SeattlePete (Post 635176)
A programmer (Predator/Trinity) can be used to change the tire size in the PCM.

As far as going from 20" to 17"- lots of factors to consider, but the main ones are overall tire diameter, rim/tire weight, and rim offset (aftermarket rims). You can go from a stock 20 to a 17, keeping the overall diameter the same, and you'll have no problems.

Would a dealership or garage do this re-calibration for you?

JHemi1 08-29-2012 11:27 AM

Quote:

Originally Posted by DrumMedic (Post 790549)
Would a dealership or garage do this re-calibration for you?

Curious about this as well :smiley_thumbs_up:

TheSatinPumpkin 08-29-2012 11:31 AM

Dealership can for a price but you 11-12 folks can purchase the Hypertech which can be used to calibrate your speedometer per tire metrics.

JHemi1 08-29-2012 03:29 PM

Interesting to know. I didn't think there was anything you could do with a programmer. But then again, if the dealer can do it, there's got to be a way. Now to find someone local lol


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