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Real Speed

The first step in understanding how your scooter performs is to know what its real speed is. All scooter speedometers read high, this seems to be a manufacturers trick to fool the customer into thinking their scooter performs better than the specification and reducing the daily load a scooter goes through at the same time. Also the difference in tyre circumference will impact accuracy e.g. a Sava MC31 has a circumference of 1360mm, whereas a Heindau racer is 1314mm, this is a 3% difference in speed readings based on the type of tyre alone.

Depending on the, front tyre, the age and model of the Vespa, the "false performance readng" varies from about +6Km/hr to +10Km/hr across the range. +10Km/hr is about standard for a new Vespa PX 200 or GT/GTS with Sava MC18's. With +6Km/hr being measured on a 1991 Vespa PX. "Across the range" means if the speedometer reads 60Km/hr, you are probably doing 50Km/hr, at a 100Km/hr reading you are only doing 90Km/hr. At higher ranges in reading can be worse, in some cases to do 100Km/hr the Vespa speedometer needs to read 115Km/hr! (Update: 12/2012 this scooter with a new 2012 replacement speedo reads 110km/hr with a real speed of 100km/hr and 60km/hr(indicated)=54km/hr(real) - Piaggio seem to be producing more accurate speedos, perhaps in response to everyone having GPS's now)

A caveat on the above statement is that due to the popularity of GPS (Global Positioning Systems) which can be purchased for less than AUS$100, more and more people are realising how bad their speedometers are. Some are fixing the problem by bending the pointer or taking the scooter back and getting it fixed as a warranty claim.

As stated the easiest way to measure speed is with a GPS.

As you can see it is pretty depressing when you think about the performance of the standard Vespa PX, when put in context of real speed. The top real speed is now more likely to be 100Km/hr, rather than 110Km/hr. When you are in that head wind, head-down in race position, looking at the speedometer struggling to get to 90Km/hr... and realising you are actually struggling to get to 80Km/hr.

Also of note is that open road and in traffic speed differ greatly. On a large motorway the traffic ahead of you raises your top speed, even a bunch of cars a few hundred metres ahead raise your speed quite a bit. This is due to aerodynamic drag playing a big role in your achievable top speed and any small reduction is seen in top speed increase. Expect to lose about +10Km/hr on the open road and this is in effect your "real top speed" because it is unaided by cars.