Given the consistency of reports of 10%ish error, I would tend to agree. However, there also seems to be a consistency to reports that the error is less or non-existent in mph speedos. I find this odd, since they come with a speedo that can give readouts in either. Has anyone compared the two different readouts for accuracy on the same bike?They must have factored a deliberate percentage gain into the speedo read out. As you said yourself your odo accuracy seems good. You will affect your odo accuracy though if you change your sprocket sizes as the pick up reads off the transmission.