speedo vs GPS

captbill51

Member

Aug 19, 2010

69

0

7

Acton, MA

Jun 14, 2011

#1

• Jun 14, 2011

• #1

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

10 Year Member

Mar 30, 2005

711

18

49

Panama City, Fl.

Jun 14, 2011

#2

• Jun 14, 2011

• #2

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

Member

Apr 18, 2003

387

1

18

Sarasota, FL

Jun 14, 2011

#3

• Jun 14, 2011

• #3

Speed/RPM Calculator

 

captbill51

Member

Aug 19, 2010

69

0

7

Acton, MA

Jun 14, 2011

#4

• Jun 14, 2011

• #4

Thanks

I can always rely on you guys

thanks jaybertx,

Bill

 

FastRedPonyCar

Founding Member

Apr 7, 2002

1,678

4

39

I pee sitting down...or do I?

Jun 16, 2011

#5

• Jun 16, 2011

• #5

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.