According to the manual, the speedo is 6% optimistic - i.e, depending on which way you calculate it, 100 is reported as either 105 or 106. I'm sure Ducati's intention is all for the best, using psychology to keep our speed down that little bit, but at least in my case it's just made me better at arithmetic. Does anybody know of a firmware fix that would get the speedo to report the _actual_ speed without correction, or what the chances are of getting Ducati to reverse this misfeature?
It's not a misfeature, it's a legal requirement in some jurisdictions. There is no chance of altering it, but GPS satnav units usually report actual speed without correction.
differing tyre designs/different tyre pressures can result in a different speedo reading despite one nominal figure being 'aimed for' so it's important as a safety feature that a slightly optimistic speedometer reading be displayed at all times to allow for this.
OK, so it's a misfeature in the law, expressed in firmware. Damn. One more reason to order a Navihalter when they're back in stock. Thanks for the explanation.
This all derives from a feature of the law known as mens rea ("guilty mind"). For most offences if an accused person did not know, nor have any means of knowing, that they were committing the offence, then that affords them a valid defence. That's why it is compulsory for vehicles to have speedometers fitted (1936 onwards) - so that drivers cannot claim they had no means of knowing they were exceeding a speed limit. For the same reason it is compulsory for speedometers not to under-read, and to be lit at night. But speedometers cannot possibly be expected to be 100% accurate all the time, given the variability of tyres, etc., so the practice is that they can over-read (by a limited percentage) but not under-read.
OK, this makes further sense. Now I'm speculating about a GPS-equipped onboard speedo that automatically recalibrates itself when it can get a clean enough signal for a long enough stretch.
