The fat factor

Discussion in 'General Questions' started by Dakman, Jul 31, 2011.

  1. Dakman

    Dakman New Member

    So has anyone any sort of idea on how much body weight affects your top speed, I feel that my bike should be faster than it is and keep looking for reasons and faults as to why it isn't, when it could just well be my fat *** limiting it. No one I know wants to ride the bike to let me see if there's a speed difference as they are scared of it and think it's dangerous so I'm wondering if there's someone who has any knowledge on this.

  2. retromike3

    retromike3 Member

    weight is an issue

    The question of weight can be a problem. A lot depends on what kind of terrain you are going along at. On my little bike (66cc Skyhawk) with a tuned pipe I have to go up some fairly steep hills. My bike does seem to slow down a bit, But these are not technically motorcycles, they are motor assisted bicycles. That being the case I set mine up with a eight speed cassette with a 11-32 gear range and a single 36 in the front. That gives me a almost one to one for a low end a really tall gear for a high. In the arcane language of Bike Speak I have a 85 inch high gear. and I can spin that out without to much trouble. I kind of like the fact that you have to pedal them a bit because otherwise, I would really get huge.

  3. motorpsycho

    motorpsycho Active Member

    here's a great example of rider weight vs. speed variances.
    ok, i weigh 150 pounds and my friend weighs 220 pounds.
    if we take turns riding my bike (a 20" stingray with a 49 c.c. 2 stroke, expansion chamber, high flow air filter and a 41 tooth rear sprocket)
    I can get it up to 30 mph on flat ground.
    if he rides it, the top speed drops to 26 mph.
    His bike is the same set up but his has a 66 c.c. on it, 100% stock with a 44 tooth rear sprocket.
    If i ride his bike, i can get 25 mph out of it. if he rides it, he will get 20 mph out of it.
    we did these little tests last summer, on the same day, same flat road and we took turns driving his car next to the bikes to go off of the speedometer in the car to get the mph.
    it may not be 100% accurate, but it did show some speed loss because of the rider weight.
  4. retromike3

    retromike3 Member

    I think size might figure in a bit

    If you and you buddy both had the same measurements regardless of weight I think the speed would be about the same because after about fifteen miles an hour the bulk of the power goes to pushing the air out of the way. thats why the fastest bike in the world is a fully faired recumbent (it goes about eighty MPH wow!)

  5. motorpsycho

    motorpsycho Active Member

    well obviously we aren't the same size...he's 70 pounds heavier than me.
    we are about the same height tho.
    whatever, we did notice a speed difference depending on who rode which bike.
  6. Sgt. Howard

    Sgt. Howard Member


    mass will play more against accelloration and hillclimb than on flat ground. Wind resistance becomes key there all other factors being equal. If you conduct the same experiment useing a BTR (board track racer) setup, there will be margional if any difference on flat ground.
    the Old Sgt.