Calibrating speedo for new tires?

I bought my truck as-is with the lift and larger tires. Is there a device that calibrates the speedometer? If so, how can I tell if I have one or that my speed is my actual speed without having the wife drive next to me on the highway? Thanks.

 

Hypertech makes an inline calibrator for our trucks - haven't used it or know too much about it.

 

It may already have one on it...I just don't know where to look for it.

 

Scanguage II

http://www.scangauge.com/

 

You could also get the ScanGauge II. I have that and adjusted my speed for the percentage size change of my tires.

Essentially, the difference was only about 2-3 MPH at 65. Before the tires, my speedo was 3 mph fast at 65. After the change in tire size, my speedo was 2-3 mph slow at 65.

 

I have the hypertech inline speedometer calibrator in my truck. It plugs in behind the speedometer. It takes a couple of minutes to hook up to your computer and enter the old and new tire sizes. Then it plugs in pretty easily. The only pain in the ass was taking the dash apart...and even that was pretty easy.

 

So both of these units (Hypertech and Scanguage) will re-calibrate the speedo? What about the odometer? Approximate cost on each unit?

 

The scangauge will display your correct speed, but I don't think it will actually change your speedometer. The hypertech unit will adjust the speedometer and odometer. But, it is expensive: about $230

http://www.jegs.com/p/Hypertech/1026990/10002/-1

 

+1. The scangauge only display information, however it's not just speed. It does ALL SORTS of stuff too! About $150-ish.

I might look in to the hypertech if, for no other reason, to keep my odometer pretty dang close.

 

This is what I'm thinking...

 

Thanks for the info. I'm assuming my speed is off.
So, if I'm running oversized tires, does that mean that the odometer is recording less miles than the truck has actually traveled?

 

I have 33's and according to my Scangauge the the odo is is reading correctly. Oddly the speedo still reads 2-3 mph fast

 

yes -- assuming there isn't a speedo recalibrator installed.

 

Ok, thanks.

 

FWIW....I recently put 35x12.5 x17's on my 05DC with a 6" lift. When my spedo showed 65mph my garmin showed 74mph.

The 35's rubbed so badly I took the truck back to the installer and had them replaced with 33x12.5's.

With the 33's the spedo and the garmin are almost in total agreement.