speedo vs GPS

[captbill51]

My speedodometer and my GPS speed does not agree.
Took "Sweet" to the dealer to have the computer adjusted.

He tried two times and we are still reading high by 5 mph.
speedo reads 80 while the GPS reads 75.

Soooo....could the GPS be off??

Could a gear head (respectfully) help me calculate rpm/mph if:

2000 rpm 6th gear 0.65 (M82) final drive 3.55
Wheel diameter 26.66 ( Circumference 83.76)

What is the MPH?

Thanks

Bill

 

[Az Pete]

I have used numerous Garmin GPs's since the 90's and have yet to find one with the speed being off. Might check it in another car.

 

[jaybertx]

Speed/RPM Calculator

 

[captbill51]

Thanks

I can always rely on you guys

thanks jaybertx,

Bill

 

[FastRedPonyCar]

have you started the car in engineering mode (google it) and compared the digital speed readout on the dash to the gps?

Also, not all GPS units are totally accurate. I would see if I could borrow a 2nd GPS unit or a phone w/gps to double check.