Legalities aside, a speedometer that reads high makes the rider think that the bike is faster than it really is. I would think that this is a good thing from a marketing perspective. It is interesting how tires effect speedo readings. Changing from a 50 to a 55 series rear tire gave me a 3% speedo correction but I lost 1.5% when the tire went from new to old. Also, speedo readings are way high when cornering due to the fact that the effective tire diameter decreases by several inches when leaned over. My winter plans are to do the 32,000 mile valve check & refresh the suspension on my cbr. Otherwise it's oil changes, stabil, & battery tenders.