Speedometer vs GPS - Can speedo be recalced?
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Joined: Apr 2008
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From: Las Vegas, NV
Speedometer vs GPS - Can speedo be recalced?
So ... with my new GPS and a long trip this last weekend, I noticed that my speedometer reads different than my GPS.
The faster I go, the more discrepancy there is.
When the GPS shows 75 mph, the speedo shows 80 ... arg ...
 \\;
Can speedos be re-calculated? or am I stuck with that?[:@]
The faster I go, the more discrepancy there is.
When the GPS shows 75 mph, the speedo shows 80 ... arg ...
 \\;
Can speedos be re-calculated? or am I stuck with that?[:@]
Cruiser
Joined: Apr 2008
Posts: 225
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From: Bellevue, Nebraska, USA, Earth
RE: Speedometer vs GPS - Can speedo be recalced?
I noticed the same thing. I just got a Garmin Zumo and when my 2008 Ultra Classic says 75 mph, the Garmin reads 70 mph. At 64 mph and the Ultra, Garmin reads 60.
I'm going to ask the same thing when I go in this week to the dealer.
I'm going to ask the same thing when I go in this week to the dealer.
Ultimate HDF Member
Joined: Jul 2006
Posts: 9,335
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From: MA
RE: Speedometer vs GPS - Can speedo be recalced?
I'm guessing this is a lag in the speedo cable compared to the GPS getting the speed off the sat. Get established at a cruise speed and then see what the difference is. I've done this and the the speedo and gps are within about 1 mph of each other. But when I accelerate/decelerate, there is a much bigger difference is speed.
Seasoned HDF Member
Joined: Feb 2007
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From: Bellevue, NE
RE: Speedometer vs GPS - Can speedo be recalced?
ORIGINAL: petemac
I'm guessing this is a lag in the speedo cable compared to the GPS getting the speed off the sat. Get established at a cruise speed and then see what the difference is. I've done this and the the speedo and gps are within about 1 mph of each other. But when I accelerate/decelerate, there is a much bigger difference is speed.
I'm guessing this is a lag in the speedo cable compared to the GPS getting the speed off the sat. Get established at a cruise speed and then see what the difference is. I've done this and the the speedo and gps are within about 1 mph of each other. But when I accelerate/decelerate, there is a much bigger difference is speed.
True, but it's usually the GPS that lags about a second behind.
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Joined: Apr 2008
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From: Las Vegas, NV
RE: Speedometer vs GPS - Can speedo be recalced?
ORIGINAL: petemac
I'm guessing this is a lag in the speedo cable compared to the GPS getting the speed off the sat. Get established at a cruise speed and then see what the difference is. I've done this and the the speedo and gps are within about 1 mph of each other. But when I accelerate/decelerate, there is a much bigger difference is speed.
I'm guessing this is a lag in the speedo cable compared to the GPS getting the speed off the sat. Get established at a cruise speed and then see what the difference is. I've done this and the the speedo and gps are within about 1 mph of each other. But when I accelerate/decelerate, there is a much bigger difference is speed.
It had nothing to do with acceleration (up or down).
Thanks for the hint, but there is actually quite a discrepancy at the higher speeds.
I hope the speedo can be recalculated.[&:]If anyone know for sure. Let us know. Thanks!
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Ultimate HDF Member
Joined: Jul 2006
Posts: 9,335
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From: MA
RE: Speedometer vs GPS - Can speedo be recalced?
Hmmmm......that was my best guess. \\; 
 \\;
 \\;
Maybe.........the refresh rate on the gps isn't that fast. I \\;know on aviation gps's they have a pretty fast refresh rate. \\;
 \\;
If that doesn't do it, I'm out of guesses. \\; \\; \\;
 \\;
 \\;
 \\;
 \\;  \\;
Maybe.........the refresh rate on the gps isn't that fast. I \\;know on aviation gps's they have a pretty fast refresh rate. \\;
 \\;
If that doesn't do it, I'm out of guesses. \\; \\;
 \\;  \\;
 \\;
 \\;
ORIGINAL: stro1965
 \\;\\\\\\;
True, but it's usually the GPS that lags about a second behind.
ORIGINAL: petemac
I'm guessing this is a lag in the speedo cable compared to the GPS getting the speed off the sat. Get established at a cruise speed and then see what the difference is. I've done this and the the speedo and gps are within about 1 mph of each other. But when I accelerate/decelerate, there is a much bigger difference is speed.
I'm guessing this is a lag in the speedo cable compared to the GPS getting the speed off the sat. Get established at a cruise speed and then see what the difference is. I've done this and the the speedo and gps are within about 1 mph of each other. But when I accelerate/decelerate, there is a much bigger difference is speed.
True, but it's usually the GPS that lags about a second behind.
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Cruiser
Joined: Apr 2008
Posts: 225
Likes: 2
From: Bellevue, Nebraska, USA, Earth
RE: Speedometer vs GPS - Can speedo be recalced?
There were four of us on a trip last week. Two of us had 2008 Ultra Classics, and the others bikes were both 2006s. The 2006s read faster and about the same as the GPS. Also, we went thru a radar warning sign that tells you the speed you are traveling. It read slower. Also tested it with cruise control and the 2008s read slower.
I definitely believe the problem is with the 2008s at least in our group.
I definitely believe the problem is with the 2008s at least in our group.
