How accurate is your speedometer

rudi · 08-15-2009, 08:22 PM

After noticing a lot of cars tailgating me, I thought I would check my speed with a GPS. I found the speed to be out minus 10 kilometers/6.2 mph when traveling at 60k/37mph. Do you think this is excessive and Is there any way to have this adjusted?

BMW Killa · 08-15-2009, 08:32 PM

Quote:

Originally Posted by rudi

After noticing a lot of cars tailgating me, I thought I would check my speed with a GPS. I found the speed to be out minus 10 kilometers/6.2 mph when traveling at 60k/37mph. Do you think this is excessive and Is there any way to have this adjusted?

You can have your speedo calibrated. That seems pretty excessive, I wouldn't expect to see more than a +/- 2 mph difference.

SDWayne · 08-15-2009, 08:35 PM

Do you have stock tires?

Wayne

rudi · 08-15-2009, 08:51 PM

Quote:

Originally Posted by SDWayne

Do you have stock tires?

Wayne

I've got the standard 18's. It's a bit of pain having to calculate your actual speed to compensate for the error all the time.

chrisw169 · 08-17-2009, 12:55 PM

I would take it to a dealer and say that its a brand new car w/ stock wheels and tires and have them fix it. That is very excessive in my opinion

need4speed · 08-17-2009, 01:00 PM

Do u really think a signal from a satellite is going to give u a better reading than ur car? Go to the track n use a laser. That should be a lot more accurate.

tooohip · 08-17-2009, 01:07 PM

Quote:

Originally Posted by need4speed

Do u really think a signal from a satellite is going to give u a better reading than ur car? Go to the track n use a laser. That should be a lot more accurate.

Yeah they are spot on! I've got two GPS units that both measure my speed identically. They are also spot on when approaching one of the "Your speed is" signs. ;-)

Chupacabra · 08-17-2009, 01:09 PM

Its usually a percentage, not an actual number that is off.

On my mini it was roughly 9% off.

the Z is a little better, at 7.7% .

TX_370 · 08-17-2009, 01:12 PM

I checked mine with my GPS and it is off about 1 MPH.

shabarivas · 08-17-2009, 01:41 PM

^ at what speed?

TX_370 · 08-17-2009, 01:43 PM

70 - 85 MPH (or 71-86 MPH, however you look at it

)

tooohip · 08-17-2009, 02:06 PM

My Z is right on, perhaps just a small fraction off at highway speeds. No more than 1 MPH at 60 though.

Modshack · 08-17-2009, 03:11 PM

Quote:

Originally Posted by need4speed

Do u really think a signal from a satellite is going to give u a better reading than ur car? Go to the track n use a laser. That should be a lot more accurate.

Again, you need to study up....

"Garmin's specifications quote 0.1mph accuracy but due to signal degredation problems, perhaps 0.5mph accuracy in typical automobile applications would be what you can count on."

havasuwiley · 08-17-2009, 10:41 PM

trust the gps

import111 · 08-17-2009, 11:49 PM

According to all the local radar stations, my speedo is dead on.

08-15-2009, 08:22 PM	#1 (permalink)
rudi Enthusiast Member Join Date: Jun 2009 Location: Australia Posts: 306 Drives: 370Z Australian Spec Rep Power: 16	How accurate is your speedometer After noticing a lot of cars tailgating me, I thought I would check my speed with a GPS. I found the speed to be out minus 10 kilometers/6.2 mph when traveling at 60k/37mph. Do you think this is excessive and Is there any way to have this adjusted?

08-15-2009, 08:35 PM	#3 (permalink)
SDWayne Base Member Join Date: May 2009 Location: San Diego Posts: 11 Drives: 09 370Z touring Rep Power: 16	Speedometer error Do you have stock tires? Wayne

08-17-2009, 01:09 PM	#8 (permalink)
Chupacabra Enthusiast Member Join Date: Jan 2009 Location: Weston, Florida Posts: 477 Drives: 09 Nissan 370z s M6 Rep Power: 200	Its usually a percentage, not an actual number that is off. On my mini it was roughly 9% off. the Z is a little better, at 7.7% . __________________ Where are my aluminum pedals?

08-17-2009, 01:12 PM	#9 (permalink)
TX_370 A True Z Fanatic Join Date: Apr 2009 Location: Texas Posts: 5,389 Drives: American Rep Power: 28	I checked mine with my GPS and it is off about 1 MPH. __________________ 2009 PW Nissan 370Z with Sports Package

08-17-2009, 01:43 PM	#11 (permalink)
TX_370 A True Z Fanatic Join Date: Apr 2009 Location: Texas Posts: 5,389 Drives: American Rep Power: 28	70 - 85 MPH (or 71-86 MPH, however you look at it ) __________________ 2009 PW Nissan 370Z with Sports Package

08-17-2009, 12:55 PM	#5 (permalink)
chrisw169 Base Member Join Date: Feb 2009 Location: Lewisville, TX Posts: 42 Drives: 93 Honda Del Sol Rep Power: 16	I would take it to a dealer and say that its a brand new car w/ stock wheels and tires and have them fix it. That is very excessive in my opinion

08-17-2009, 01:00 PM	#6 (permalink)
need4speed Base Member Join Date: Jun 2009 Location: tx Posts: 199 Drives: 08 altima 3.5se Rep Power: 16	Do u really think a signal from a satellite is going to give u a better reading than ur car? Go to the track n use a laser. That should be a lot more accurate.

08-17-2009, 01:41 PM	#10 (permalink)
shabarivas A True Z Fanatic Join Date: Apr 2009 Location: Sacramento, CA Posts: 2,188 Drives: 370z MB 6mt Rep Power: 914	^ at what speed?

08-17-2009, 02:06 PM	#12 (permalink)
tooohip A True Z Fanatic Join Date: May 2009 Location: Columbia, MD Posts: 1,626 Drives: 09 370z CY To/Sp Rep Power: 270	My Z is right on, perhaps just a small fraction off at highway speeds. No more than 1 MPH at 60 though. __________________ Lance KW Variant 3 Coilovers \| Stillen Sways \| Stillen Gen III Intake \| AAM HFC \| AAM True Dual CBE \| AAM Comp Oil Cooler \| Hawk HPS Pads \| Volk TE-37 \| Hoser Keg Tap

08-17-2009, 10:41 PM	#14 (permalink)
havasuwiley Base Member Join Date: Jul 2009 Location: lake havasu city az Posts: 131 Drives: 09 370z, 03 z06 etc Rep Power: 16	trust the gps

08-17-2009, 11:49 PM	#15 (permalink)
import111 Track Member Join Date: Feb 2009 Location: Tucson, AZ. Posts: 622 Drives: 09 Nissan 370Z Rep Power: 191	According to all the local radar stations, my speedo is dead on.

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