I've had the CTS for a long time and not knowing what a lot of the stuff meant I just used it to monitor stuff. When I tried to load program 1 or 2 the speedometer says 80 while the gps says 70. I don't get it. The tires are 285/70 r17 and entered properly.

 

 

Thanks for pointing that out. I looked it up and changed it to 3.55.

 

 

Driving around my speedometer is 1 mph off of the CTS and the CTS is 1 mph off from the radar on a speed limit sign (you know the ones that tell your speed as you approach a speed limit sign). Is there a way to adjust the speedometer and the CTS?

 

 

or dont worry about it
Tire size can change by 3/4" between new and worn tread.

 

This^^ plus the level of accuracy on all the devices can vary thus giving you different measurements. Don't worry about 1mph.

 

Already did it.

Thanks.

My gps also matches the speed sign so I'm inclined to believe the two that are the same.

Thanks.