larger tires, slower speed!

really? that's it, good I thought it would be more

 

Actually, depending on the tires from the factory. I believe my 17" Dunlops were 30.6. My GPS reflects a higher speed than what my speedo is showing. Up to several miles difference depending on the speeds.
If everyone is correct, when I remove those POS in the fall and replace with a slightly larger tire, the speedo should read closer to actuals on my GPS.

 

... since getting bigger tires, my speedo appears to be just about right on with my GPS. My odometer doesnt read the same as the GPS though. So those that are riding on larger tires actually have more miles on their truck than what the Odo is reading.