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Anyone test the accuracy on the Sportster speedometer?
I test ran my Triumph with a GPS and the speedo was of by about 7% across the useful range.
 

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The stock speedo on my 92 fxr is dead on accurate when compared with a gps. They always read exactly the same.
 

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HATER OF THE GRAVEL!!!!!!
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Many manufactures these days will have there speedo'd read a bit faster then they are going to avoid being sued for someone getting a speeding ticket for having a speedo that reads slower then you are going.
Tores wear and brand can change it as well. I have the S&S calibrator on my bike and I have it dialed to read 60MPH @59.2MPH. It is as close as I could get it.
 

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2 options I see. Get a GPS and go on a straight road thru the different speeds to see where it shows an issue is one. The other is to borrow one of those speed warnings that show you your speed and drive up to it and see what it sees vs what your speedo says.
 

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My 2006 Roadster is about 1-2 mph off from the GPS at 50-60 mph.
 

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2 options I see. Get a GPS and go on a straight road thru the different speeds to see where it shows an issue is one. The other is to borrow one of those speed warnings that show you your speed and drive up to it and see what it sees vs what your speedo says.
I've noticed that those signs seldom agree with my Garmin. I'd like for any LEOs reading this to chime in. I'm not looking for room to cheat, I just like accurate info.

My work truck reads 2 MPH slower than Garmin at 70-75. My FXR reads 3-4 MPH slower at 65, but that's with a Custom Chrome speedo.

Also, the same size tire, from different makers, will vary in diameter. That affects accuracy too; though I'd like to know if that difference is a practical one, or only a theoretical one.

joe
 

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I find the all Garmin's I have had, the 265T, the 220 and the 550 have all read the same on the gps as the speed warning signs. I use cruise control in the car so I knew the steady speed the gps indicated. It was always within one mile per hour of the speed road sign. And it was also within 1 mph of the speedo on my Ford Escort. They all read just about the same for me. The same is true, as I mentioned earlier, for my 92 fxr. They all consistently read within 1 mph of each other.
 
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