Speedo or GPS?

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Aug 1, 2016 | 04:09 PM

#11

DanRC

Road Master

Joined: Dec 2012

Posts: 755

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From: Sartell, Minnesota

My GPS on my CVO gives me the same speed as the speedometer. When I use a gps on my RKC, my speedo shows about 3 mph more than the gps.

Aug 1, 2016 | 04:13 PM

#12

shorelasHD

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Joined: Oct 2010

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From: SW FL-Jersey Shore Emigre

As a rule, speedos aren't terribly accurate. I've had a Honda ST1300 where the speedo read 5-7% faster than the GPS or radar, and I ended up getting a SpeedooHealer to correct it.

On the other hand, all 3 of my Harleys are within 0.5 MPH of GPS at highway speeds, anyway. Go figure.

Aug 1, 2016 | 04:30 PM

#13

MilesOfTexas

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Joined: Mar 2012

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From: Central TX

Quote:

Originally Posted by DanRC

My GPS on my CVO gives me the same speed as the speedometer. When I use a gps on my RKC, my speedo shows about 3 mph more than the gps.

If your CVO is a Rushmore and is the built in one, it will always give the same speed as the speedo because it isn't reporting speed from satellites, but rather from the ecm. If it is a stand-alone GPS, then you are a lucky guy.

Aug 1, 2016 | 04:40 PM

#14

ev780

Tourer

Joined: Dec 2008

Posts: 494

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From: Colorado Rockies

Quote:

Originally Posted by rscalzo

A gps is not a great speed measurement device. in fact the courts have ruled it to be unreliable for speed.

GPS doesn't get constant updates but random ones. GPS will usually lag.

Quote:

Originally Posted by akodust

GPS is communicating 33K miles to at least 3 satellites to get your coordinates, that takes about 2 seconds. that lag time makes a difference.

Maybe those things are true but, the math behind GPS speed calculation is exceeding accurate. Running down the road and watching the speed display will be close enough for the human brain. If accelerating or decelerating there may be a delay. But on average I trust GPS. In fact i got into my ecm when tuning my Roadie and corrected the factory speedo to match Garmin.

Aug 1, 2016 | 05:07 PM

#15

0ldhippie

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Joined: Mar 2012

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From: Santa Cruz

Gps may "lag" speed and/or direction changes but are very accurate at straight steady speeds. Speedos are purposely calibrated 3-5% fast and are effected by tire changes and/or wear.

Aug 1, 2016 | 05:58 PM

#16

Alter Kaker

Senior Rider

Joined: Dec 2008

Posts: 251

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From: Vancouver Canada

Speedo/GPS

On my Mazda B3000, the GPS shows me doing 60 when the speedo shows about 63-4.
Same GPS on the Electra Glide shows the bike speedo is slow by about 2.
Remember, the manufacturers also use the odometer with much the same error to short out the warranty claims too.
By the way: Who EVER said the non-polce bikes had calibrated speedometers?

Aug 1, 2016 | 07:54 PM

#17

todd-67

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Joined: Jun 2009

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From: OH

Quote:

Originally Posted by 0ldhippie

Gps may "lag" speed and/or direction changes but are very accurate at straight steady speeds. Speedos are purposely calibrated 3-5% fast and are effected by tire changes and/or wear.

I agree. I use my zumo in my truck as well as the bike. Truck is only a mile or two off bikes are around 4%

Aug 1, 2016 | 08:07 PM

#18

skratch

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Joined: Jan 2007

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From: anacoco, la

Quote:

Originally Posted by Alter Kaker

Remember, the manufacturers also use the odometer with much the same error to short out the warranty claims too.
By the way: Who EVER said the non-polce bikes had calibrated speedometers?

not so much an issue with hd. the warranty is not mileage based, but time based. no matter how off your speedo is, a day is still a day.

as far as calibrated speedos go, hd used to use them. the speedo on my 2002 sportster was calibrated. it'll say on the face 'certified'