2nd Gen Non-Engine/Transmission speedometer correction?

[kbond]

Does anyone know of a device or method to correct the speedometer after installing larger tires? I just installed 37" tires and I know its way off.



Thanks for the help,



-Ken

 

[athompson]

This box will do it.



https://www.turbodieselregister.com/cgi-bin/classifieds2/classifieds. cgi?session_key=&search_and_display_db_button=on&db_id=579&query=retrieval

 

[CumminsPower98]

Here is a site listing what I use: http://www.biggertrucks.com/website/tru_speed.html



The Superlift Truspeed works very well and even has a two position switch to allow for two sets of tires.

 

[C. Harlan]

Use a GPS, and save mileage on your truck! I have 285-75-16's on my truck, and I figure It has saved 15,000 miles on my dash, as the clock is showing 170,000, and I calculate it to be around 10% off... . think about that before you alter the OD... .





-Chris-

 

[jmtandem]

speedometer error

I used a handheld GPS and drove at different speeds to calibrate a correction card as my truck has 285 tires. The speedo error is about 9 percent, it reads 65 and the truck is actually traveling a little over 70 mph. Suppposedly GPS is accurate to within one tenth of a mile per hour over 5 mph.

 

[Mark Baker]

I agree with leaving the speedo/odometer alone. My tires (35" diam) equillibrate to exactly a 10% increase in speed/distance. A simple calculation- 60=66mph, 1,000mi=1,100mi. traveled.