OK, i got 32 inch tires and adjust the speedo with my tuner and GPS - my question is will the larger tires throw off the odometer reading for mileage. which will then not give me accurate MPG readings...?????????????

 

Yes--if you get a tuner, you can adjust for tire size though.

 

Hmmm, I did adjust the mph with tuner.. would that also adjust odometer?

 

this is a very good question. never really thought of it. i would imagine the odometer and speedo would both be recailibrated when you calibrate the speedo seeing as they both use the same sensors to measure speed and mileage

 

It should yes.

Just go drive a mile on the interstate or somewhere with mile markers in order to use them as a gauge - then verify that your odometer also moved a mile.

Or use a GPS or smartphone App that records distance....

 

^^^^^^^

 

Depending on your model and setup. I'm assuming 4x4. Your speed signal will be coming from a hall effect sensor either on the transmission or the rear end housing. This signal is a pulse signal. The GEM (2wd pre-2001) or 4WABS (4x4 or 2001-up 2wd) will convert this pulse signal into a voltage that is sent to the cluster. This voltages splits to the speedometer and the odometer so they both read the same. I've noticed that factory readings are always off about 2 units between odometer and speedometer. Odometer usually reads dead on but the speedometer always reads about 2 mph faster than what you are really going.

If your a real accuracy stickler I would get your odometer to read correctly and then adjust the needle on the speedometer manually (removing and setting cruise to a known speed and re applying the needle).

Note GPS speedometers are acurate to about 0.1 of a mile.

 

That is not true. Not in either one of my rangers or any of my other 3 vehicles since then. Might just be your truck but your speedometer should be dead on.

 

well i tested it out..
zeroed the truck, GPS, and Ultragauge. and drove....
Truck read 30.2 miles
Ultra gauge read 29.9 miles
and GPS read 30.71 miles

i dont think its really enough of a difference to worry about

 

Yep, good to hear - it looks like the tuner dialed in both the speedometer & odometer.

 

This is good to know. Never thought about the odometer not changing but glad to hear it does...

 

Look at the Speedometer section here: http://www.therangerstation.com/tech_library/index.php

The Ranger Station - Technical Library