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#25 Factors Affecting Top Speed and Mileage

May 29, 2012

As with our last installment, I’m not addressing a specific question, but a lot of questions or conversations I’ve heard about motorcycle or scooter top speed and mileage:

Why do other scooterists report better mileage or a higher top speed than I seem to get from my scooter?

or

Why does my mileage seem to fluctuate so much?

or

Why am I not getting the mileage promised by the brochure?

Sometimes I get the impression that folks don’t realize how many factors can affect both mileage and top speed. Both can vary immensely depending on a variety of conditions. Some of these variables make a bigger difference than others, but all together, they make scientific comparison very difficult.

What factors can affect your mileage or top speed? Here are a few dozen off the top of my head, I’m sure commenters can offer more.

  • Weight
    Body/clothing weight variations
    Passenger
    Cargo and luggage
    Weight of fuel in the tank (full vs. empty tank)
  • Aerodynamics
    Cargo
    Clothing
    Accessories/windscreen
  • Weather
    Wind direction/speed
    Temperature
    Altitude/Barometric pressure
    Humidity
  • The Road
    Riding style (aggressive acceleration/braking)
    Open road vs. traffic/lights
    Surface temperature
    Surface texture
    Grade (uphill/downhill)
    Direction (straight line or curves)
  • Fuel
    Freshness
    Quality
    Octane (NOT a measure of “quality,” use the proper octane, higher isn’t better!)
    Weight of fuel in tank
  • Tires
    Inflation
    Quality/tread design/intended use
    Tread wear
    Temperature
  • Engine
    Cleanliness
    Adjustment of valves, timing, compression
    Cleanliness/design of fuel/oil/air filters
    Obstructions in airflow
  • Speedometer/Odometer calibration
  • Perception and Confirmation Bias
    If I’ve learned anything on the forums, it’s that there are people who have their own ideas about their mileage and/or top speed, and nothing anyone can say will convince them otherwise. If the brochure said the top speed was 60mph and the bike offers 120mpg, well, they’re getting even better than that, damnit! If they’re not, it has nothing to do with the factors above, it’s a defective bike, or their shop screwed something up last time they were in. No, really, they can FEEL it! Take any measurement of top speed with a grain of… well, unless salt flats and a lot of timing technology were involved, don’t believe it. Same with mileage, if a notebook, a graduated cylinder, and a full year or so of measurements aren’t involved, it’s just anecdotal. And even then, that rider’s conditions may vary wildly from yours.

To specifically answer the last question, “Why am I not getting the mileage promised by the brochure?,” The answer is simple. The mileage figure quoted in the brochure IS attainable. All you need to do is lose 140 pounds, and ride on a perfectly level sheet of stainless steel, at 65°F with a 25mph wind at your back. Be sure not to accelerate, decelerate, or stop, and keep the engine at 1210 RPM, just above idle. Eventually you’ll work your way up to 25, maybe 30mph, but you’ll be getting great mileage.

Do you have a question for the 2strokebuzz experts? Email Dr. Buzz! Your confidentiality is guaranteed.

Note: Dr. Buzz is an unlicensed, mostly-fictional doctor. Take his advice, and that of his team of experts, with a grain of salt.

Comments

One Response to “#25 Factors Affecting Top Speed and Mileage”

  1. duoNo Gravatar on June 11th, 2012 1:38pm

    EPA Estimates for Scooters are done with a top speed of 30mph, so that one could compare across displacement.

    So it is unlikely that anyone with an engine larger that 50cc will get the estimated mpg since they will go faster, else why bother with more displacement.

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