My SS9 over reports 13% and I hate it. It is by far the biggest tacho error I have seen in all European vehicles that I own(ed). The odometer is spot-on precise. I have complained, but Energica are saying that they compliant with EU law and it's true. EU law has a formula that allows up to 15% over-reporting. I find the error more annoying than the top speed not being met.
I have a GPS on all my bikes anyway, so I know what speed I am really going. I do not find the inaccuracy to be a big problem, but the Energica is the highest readings I have ever seen. 5% over would be a lot more reasonable.
People also complain about the TTSE readings being high (in the TTSE Forum) that are less than half as bad as the Energica.
The Enrgica is so ridiculously high, it might as well not have a speedometer at all, IMO, unless one can get used to what readings they want to see for what real MPH. It is so far off that it askes to be ignored.
-Don- Reno, NV