Mileage Variation

[AGT]

My brother just bought an 06 with a lift. His friend is telling him that when trucks are lifted they are off 10% on the odometer and Speedo, so the truck shows 40980 on the mileage it actually has about 45000 miles. You have to have a chip down and it cleans it all up and makes it run better. Is this true?

[dlewis1111]

My brother just bought an 06 with a lift. His friend is telling him that when trucks are lifted they are off 10% on the odometer and Speedo, so the truck shows 40980 on the mileage it actually has about 45000 miles. You have to have a chip down and it cleans it all up and makes it run better. Is this true?

 

Lifting the suspension itself has no effect on the speedometer / odometer. What affects it is larger overall diameter tires that usually come with it. A properly done lifted truck with bigger wheels will have been reprogrammed to correct the problem with not only the speed / odo, but the ABS system, transmission shifting, and stabilitrak if equipped. And the ten percent rule is off too. Ten percent at 30 miles per hour is only 3 mph. Ten percent at 80 is 8 mph. There is usually a point when the speedo is accurate and then goes back out, like a bell curve. Take the truck to the dealer and have them hook the tech II up and see if it has a custom tune. This will answer your question.

[AGT]

Thank you sir

[Rat4go]

Lifting the suspension itself has no effect on the speedometer / odometer. What affects it is larger overall diameter tires that usually come with it. A properly done lifted truck with bigger wheels will have been reprogrammed to correct the problem with not only the speed / odo, but the ABS system, transmission shifting, and stabilitrak if equipped.

 

I agree with the above.

 

And the ten percent rule is off too. Ten percent at 30 miles per hour is only 3 mph. Ten percent at 80 is 8 mph. There is usually a point when the speedo is accurate and then goes back out, like a bell curve.

 

I don't agree with this. I agree that the % is a fxn of the tire change so assuming 10% is dangerous unless you know the old tire size and the new tire size. However, if you don't accout for it in the calibrations, your speedo/odo will ALWAYS be off by the 'ratio' of the old tire 'height' divided by the new tire 'height'.

 

Example: If you go from 30" tires from 33" tall tires, your speedo and ODO will read about 91% of actual speed/distance. You'll read about 45mph when you're really doing 50 mph, ODO will accumulate about 45000 miles when you really traveled 50000. The speedo/odo is ALWAYS off by this %.

 

The only place it's accurate after a tire (or axle) change that was not accounted for is at 0 mph!

 

Another easy way to check this is using a GPS.....everyone's got em now and you can compare GPS speed (pretty accurate from my experience) to speedo indicated speed. If speedo is low by 10%, ODO will be low by same %.