Most of the time the odometers are accurate but the speedometers are not. Do a mileage check on your odometer on a measured mile or five miles.

 

Good idea using a measured mile to check odometer accuracy.

 

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.[

 

My speedometer is accurate...... calibrated to my GPS using my Power Vision.

 

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.

 

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!

 

Yeah, you would think if you signed a disclaimer at the dealership that they could calibrate it.

 

Sign of the times.....

 

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.

 

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.