Speedometer Accuracy

Bill #4 Explorer · 02-24-2011, 11:47 AM

2011 Limited

I checked the accuracy of my speedo, and digital readout (when in cruise control) today VS my Garmin (I know it to be dead-on accurate) and as expected the Explorer reads out slightly fast.

Only 1 MPH. This is very-very common with many cars I own. My prior Explorer, the 2007, was off (fast) by 3 MPH.

So, when the speedo says I'm doing 70 MPH I am actually going 69 MPH.

Have any others checked the accuracy?

uniquename · 02-24-2011, 11:54 AM

You can't really say it's X mph off. It's proportional, if you recheck at a lower speed, it shouldn't be the same off as at 70 mph.

w1kedz · 02-24-2011, 12:00 PM

Quote:

Originally Posted by Bill #4 Explorer

2011 Limited

I checked the accuracy of my speedo, and digital readout (when in cruise control) today VS my Garmin (I know it to be dead-on accurate) and as expected the Explorer reads out slightly fast.

Only 1 MPH. This is very-very common with many cars I own. My prior Explorer, the 2007, was off (fast) by 3 MPH.

So, when the speedo says I'm doing 70 MPH I am actually going 69 MPH.

Have any others checked the accuracy?

GPS by design is inaccurate in positioning. They use a smoothing algorithm to calculate speed. Speed on the gps will vary +- .1 to .5 mph with more than 3 satellites connected. With rounding that could be where your 1mph difference is. So when the gps says you are going 69, you may be going 69.5 and the speedometer would round this to 70mph ..

~w1kedz

K-Rod · 02-24-2011, 03:22 PM

I also think it is off and had suspected that myself. We have the speed signs where I live and they have one up now and it shows me going slower than I think I am. Better than the other way around!

fedyfedz · 02-24-2011, 03:27 PM

a little off topic but the speed signs dont pick up my truck for some reason, ive tested this one many times even had a friend try same speed in his 2003 explorer ....

**JDraper** · 02-24-2011, 04:36 PM

Quote:

Originally Posted by K-Rod

I also think it is off and had suspected that myself. We have the speed signs where I live and they have one up now and it shows me going slower than I think I am. Better than the other way around!

Speed signs aren't necessarily calibrated correctly. We have had several in our area, and each one reads a little differently. Driving the same vehicle, I've seen up to a 5mph difference when driving past them at the same speed.

02-24-2011, 11:47 AM	#1
Bill #4 Explorer Wannabe Elite Explorer Chicago Area 2011 Explorer Limited Join Date: Feb 2011 Posts: 774 Vehicle Specs (Original Poster)	Speedometer Accuracy 2011 Limited I checked the accuracy of my speedo, and digital readout (when in cruise control) today VS my Garmin (I know it to be dead-on accurate) and as expected the Explorer reads out slightly fast. Only 1 MPH. This is very-very common with many cars I own. My prior Explorer, the 2007, was off (fast) by 3 MPH. So, when the speedo says I'm doing 70 MPH I am actually going 69 MPH. Have any others checked the accuracy?

02-24-2011, 03:27 PM	#5
fedyfedz Wannabe Elite Explorer Suffolk County, NY 2002 limited v8 Join Date: Apr 2010 Posts: 899 Vehicle Specs	a little off topic but the speed signs dont pick up my truck for some reason, ive tested this one many times even had a friend try same speed in his 2003 explorer .... __________________ Sold 2002 explorer v8 limited Current Ride:2001 Dakota v8 Registry

02-24-2011, 11:54 AM	#2
uniquename Wannabe Elite Explorer Twin Cities, MN '11 XLT Join Date: Mar 2008 Posts: 546 Vehicle Specs	You can't really say it's X mph off. It's proportional, if you recheck at a lower speed, it shouldn't be the same off as at 70 mph.

02-24-2011, 03:22 PM	#4
K-Rod Wannabe Elite Explorer Pinehurst, NC 2011 Explorer Limited Join Date: Feb 2011 Posts: 24 Vehicle Specs	I also think it is off and had suspected that myself. We have the speed signs where I live and they have one up now and it shows me going slower than I think I am. Better than the other way around! __________________ 2011 Explorer Limited Extra fun stuff: moon roof, power liftgate, tow package Riding around in a lounge chair with surround sound