Speedometer accuracy?
Supporter
Joined: Aug 2008
Posts: 5,189
Likes: 16
From: N.E. Wisconsin
Here's a cut from the Wikipedia.
Vehicle manufacturers usually calibrate speedometers to read high by an amount equal to the average error, to ensure that their speedometers never indicate a lower speed than the actual speed of the vehicle, to ensure they are not liable for drivers violating speed limits.[
Vehicle manufacturers usually calibrate speedometers to read high by an amount equal to the average error, to ensure that their speedometers never indicate a lower speed than the actual speed of the vehicle, to ensure they are not liable for drivers violating speed limits.[
Outstanding HDF Member
Joined: Jul 2007
Posts: 2,241
Likes: 7
From: Daytona, Fla.
Most Harleys are 3 to 5 mph optimistic. Better than BMW, but still a little annoying. One of the nice extras with the ThunderMax Auto Tune is the ability to adjust the speedo. Mine is now within one half mph of my Zumo.
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Road Captain
Joined: Feb 2012
Posts: 507
Likes: 5
From: Florida
This gets very interesting. If auto tune can calibrate the speedometer, why can't the service department perform the same?
I've read the "disclaimer" posted from WikiPedia but that like everything else nowadays......a cop-out!
I've read the "disclaimer" posted from WikiPedia but that like everything else nowadays......a cop-out!
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Road Captain
Joined: Feb 2012
Posts: 507
Likes: 5
From: Florida
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Road Warrior
Joined: Aug 2007
Posts: 1,599
Likes: 7
From: Hoffman Estates, IL
Mine is off by about 1 @ 30, 2 @ 60, 3 @ 80, all to the positive.
Every bike I've ever owned (except for my '96 Road King, which had a certified speedo that was only 1% off at 100MPH) was off. Always to the positive, HD's from 3-5%, metrics up to around 10% @ 60MPH.
Never really minded it... Checked against GPS and the occasional bike-friendly LEO, re-check occasionally when I'm buzzing around just to make sure it stays consistent.
Every bike I've ever owned (except for my '96 Road King, which had a certified speedo that was only 1% off at 100MPH) was off. Always to the positive, HD's from 3-5%, metrics up to around 10% @ 60MPH.
Never really minded it... Checked against GPS and the occasional bike-friendly LEO, re-check occasionally when I'm buzzing around just to make sure it stays consistent.
Cruiser
Joined: Nov 2012
Posts: 236
Likes: 113
From: Georgia
Left uncorrected motorcycle speedometers are a 5-10% off (showing u are going faster than you actually are). So the faster you go the more it is actually off. I hav owned a couple of bikes where they were really close, maybe even correct.
So if you do the math (using easy numbers of 10%):
10mph (indicated) actually equals 9mph,
100mph (indicated) actually equals 90mph.
Never bothered me so I have never corrected a speedometer.
So if you do the math (using easy numbers of 10%):
10mph (indicated) actually equals 9mph,
100mph (indicated) actually equals 90mph.
Never bothered me so I have never corrected a speedometer.