Like many over the years I have owned different odometers. Using the chart for the tire sizes I have found that they are not always accurate. So I do a roll out measurement to get the correct number of cms. I know the chart numbers can be affected by the psi of the tire. Even after using an accurate measurement I may come up 25 yards over or under a measured mile when riding. My wife says, "Who cares?" But to me over time those extra feet add up, or take away from your true riding distance. She thinks I have OCD. Which brands on the market seem to be giving the most accurate readings?