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Page last modified 00:09, 7 Jul 2011 by internetscooter
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Vespa Labs > Vespa 101 > Dynamics > Real Speed

Real Speed

From $1

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    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!

    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.

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    Comments (4)
    Viewing 4 of 4 comments: view all
    #1
    Dedalo says:
    And of course, not only is the speedometer useless on a PX, but also the odometer. Whatever reading you've got, multiply it by 0.9 to get closer to real distance covered. In point of fact, of the 7 instruments on a brand new PX gauge, only 3 actually work properly: the headlight indicator, the high beam indicator, and the right/left indicator. The fuel gauge (at half tank reading, the tank is way less than half full), the speedometer, the odometer, and fuel light (you can do anywhere between 50 to 25 kms when the fuel light comes on) are all woefully inaccurate. A properly functioning headset gauge (aftermarket, German made?) made for a Vespa PX is a real desideratum! edited 22:44, 10 Jun 2009
    Posted 22:44, 10 Jun 2009
    #2
    internetscooter says:
    Dedalo - I've just been travelling to Torquay several times ove the last month and that is about a 240km round trip. I decided to check the odometer as well as speed.

    For speed, I found that to sit on 100km/hr I needed an indicated 115Km/hr.

    For distance however if I did 100km the odometer moved 105km.

    The above was measured using a bicycle computer calibrated against a GPS and a road speed indicator.
    Posted 12:17, 10 Nov 2010
    #3
    Dedalo says:
    Those figures sound believable to me. I lived 4 years in Torquay when I was a kid. It was great growing up there, but people tell me it's part of the urban sprawl now. Did you ride your Vespa on the Great Ocean road? That would be a fantastic ride!
    Posted 21:44, 12 Mar 2011
    #4
    internetscooter says:
    yes to both - a lot of development going on there - mostly Geelong people I guess. Done the Great Ocean Road a few times and it lives up to its name!
    Posted 21:44, 13 Mar 2011
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