I conducted a scientifically based test check of my odometer (means I checked it over the course of 10 mile markers along the hiway {;P and it seems my odometer is reading 15% low. That means I'm traveling more miles than are being recorded. So my mpg instatnly went from 13.5 to 15.5. Yippee

But I'm wondering if the speedometer is a separate system (03 RAM Quad cab) than the odometer. I haven't run a stop watch, but gut feel after driving the same route for 3 years in my other vehicle is that the speedometer is fairly accurate. I would notice if traffic was going 75 instead of 65 (approx. 15% increase).

Anyone know if the speed is calculated off something different than the distance on a 2003 RAM Quad - 275 x 55 x 20" tire package

thanks

 

both the odometer and speedo run off the same sensor.

I can bump my speedo against my GPS and I get a 2mph difference. speedo says 70, gps says 68.

 

Mine's dead-on with my GPS

 

and your odometer is just as accurate? Does the odometer agree with the GPS distance traveled?
I'll check my speedometer with the stop watch, then I'll know if something's goofy here.

Thanks for the input

 

never looked at that. . .I have a 300 mile trip comeing up, will check it out

 

I'd check it against a GPS. I think that speedometers are allowed to have up to a 2-3% error. Also, make sure the tires are at the correct PSI.