Mileage way off

[northshoremb]

Hello I have had my JScan set to all my jeep parameters and tire size as it sits on ground like says to measure but when I check odometer vs actual distance on Google earth I'm off by .14km roughly and can't get it close. I literally set odometer and drive exactly 1km then do google earth maps and it says 1.14km. So I adjusted tire a bit (smaller cause that's what internet says is a smaller diameter will bring it closer) but now I have JSCAN set 2" smaller tire than it measures and still off. Just checked 2km and 3km odometer reading and at 3km on odometer it's actually 3.44km. Yes gear ratio is set to 3.45 cause that's what's in this model and everything else looks right and matches the VIN decoder specs

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[jludave]

now I have JSCAN set 2" smaller tire than it measures and still off.

Get something flat and lay it across the top of one of your tires so that it is perpendicular to the tire. Measure from the ground up to that. Enter that measurement, minus 0.5 inches, in JSCAN.

From the JSCAN documentation:

• Choose a value from the drop-down list. It represents a tire diameter in inches.

Note
If you pick a value that matches your tire size exaclty, your speedometer will be showing a higher reading than your GPS. That’s normal - your factory wheels with factory settings worked the same. Blame the law-makers (At least in the EU). We recommend setting a value that is about 0.5 inch smaller than your actual tire size.

 

[northshoremb]

Get something flat and lay it across the top of one of your tires so that it is perpendicular to the tire. Measure from the ground up to that. Enter that measurement, minus 0.5 inches, in JSCAN.

From the JSCAN documentation:

• Choose a value from the drop-down list. It represents a tire diameter in inches.

Note
If you pick a value that matches your tire size exaclty, your speedometer will be showing a higher reading than your GPS. That’s normal - your factory wheels with factory settings worked the same. Blame the law-makers (At least in the EU). We recommend setting a value that is about 0.5 inch smaller than your actual tire size.

Thats exact what I did. Put a level on top tire then measured to ground and inputted that

 

[jludave]

Thats exact what I did. Put a level on top tire then measured to ground and inputted that

Did you subtract 0.5 inches as per the note above?

 

[northshoremb]

I tried .5 then 1" then 1.5" then 2" and still off

 

[northshoremb]

Did you subtract 0.5 inches as per the note above?

Just got off work so I went totally opposite way and increased size so jscan was showing bigger than what tires measured and now it's close. I had to select 1" bigger to get close and still just a little off so going to try 1.25 and 1.5" over what they measure. Just want accurate mileage and MPG

 

[Bobby Hank]

It's because you're using kilometers instead of miles. No one, not even car computers, understands the metric system, because it isn't real. How long is a kilometer? No one knows... it could be a mile, 10 miles, 4 inches... impossible to say.
Drive down to the border, cross it, calibrate your tires using miles, feet, inches, measurements based in reality. All will be well.
Your gas mileage will make more sense too, as I assume if you're whacky enough to use kilometers that you're also using liters. So there is no way to tell the size of your gas tank or how much fuel you're putting in or have. Miles per gallon is easy to figure. Kilometers to liters? Cannot be done.

So while you're measuring your tires, buy gallons of gas. Don't look for petrol, we don't have that here either. It'd be best if the tank was nearly empty when you do this, but if you're measuring your fuel in liters, there is no way to know ahead of time.
Good Luck!!

#PutThatInYourPipe

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