On the frame or around the middle

Discussion in 'General Cycling Discussions' started by 12boy, 8 Feb 2019.

  1. 12boy

    12boy Über Member

    Location:
    Casper WY USA
    I have often found in discussions about bike weight the idea that instead of paring down the weight of the bike it would be just as good if not better to lose some weight on the rider. I believe heavy tires, tubes and wheels make a disproportionate difference, but how about the rest of the bike? Assuming an identical amount of muscle and fitness, for example, would 180 lb rider on a 20 lb bike need the same energy to climb a hill or against a headwind as a 170 lb rider on a 30 lb bike. To isolate the weight factor let's also stipulate the same positions, handle bars etc.. perhaps this has been chewed to death already, and if so I apologize.
     
  2. OnTheRopes

    OnTheRopes Regular

    It is always better for the rider to lose weight, and cheaper, as long as you are not already at your best race weight. I lost 8Kgs off my body after a year off the bike and back into training, try losing that much off the bike.
    As far as your example goes that depends on too many variables. Is the rider overweight at 180lbs, is the rider underweight at 170lbs and at what level of fitness are they I suppose?
     
    raleighnut likes this.
  3. Smokin Joe

    Smokin Joe Legendary Member

    At 6' tall and 67kg dripping wet, I think I'll stick to shaving a few grams off the bike here and there.

    Back in the day there were no fat cyclists, people eat too much and eat the wrong food now.
     
  4. Yellow Saddle

    Yellow Saddle Veteran

    Location:
    Loch side.
    Believe again.
     
    nickyboy likes this.
  5. rogerzilla

    rogerzilla Guru

    Heavy rider, light bike handles better than light rider, heavy bike, especially standing up. If your legs are the springs, the bike is unsprung weight.
     
  6. pjd57

    pjd57 Über Member

    Location:
    Glasgow
    What direction is the wind blowing at the time ?
     
    Cuchilo, Illaveago and raleighnut like this.
  7. Oldfentiger

    Oldfentiger Über Member

    Location:
    Pendle, Lancs
    Assuming the two riders have the same athleticism, the heavier rider will produce more power.
    Given the total weight of each combination is the same, the heavier rider/lighter bike combo will have a better power to weight ratio.
    Of course that could be bollox ^_^
     
    pjd57 likes this.
  8. rogerzilla

    rogerzilla Guru

    It's a lot easier to bunnyhop a light bike.
     
    SpokeyDokey and Cuchilo like this.
  9. Ajax Bay

    Ajax Bay Veteran

    Location:
    East Devon
    System weight (rider + bike) increase/decrease matters if the route has significant amount of climb but otherwise it doesn't make much difference. Doesn't matter where the weight is 'pared' from. Important that the rider's power output is not adversely affected by reduction in (body) weight.
    https://road.cc/content/feature/213...heel-weight-doesnt-matter-and-how-wind-tunnel
    "Swiss Side feed aero and weight data into a model that crunches the numbers for different types of ride profile and length, and then spits out the likely speed and timing penalties based on a reference ride. One of their programs is a 120km rolling ride with 1200m of height gain. Their 'average' rider completes this parcours at exactly 30km/h (211.4W average power) . . . What difference would one hundred grams (from an 8kg bike to an 8.1kg bike, with a 75kg rider) do to the ride time?
    "Well, it would increase it. By three seconds."
    "Heavy tires, tubes and wheels make" a proportionate difference. Only in rides/races designed to incorporate lots of braking and subsequent sharp acceleration (eg urban crits) will increased rotating weight (ie the wheels) require a higher average power for the same speed/time but the aero performance of the wheel/tyre combo is more important (see link).
    Climb hill - I've addressed. Against a headwind - if the bikes have the same Cd then the heavier rider may be bulkier and therefore experience more drag, but 4.5kg difference will make little difference to the body's physical dimensions and its Cd. I suppose the lighter rider might be more 'flexible' and get down on the drops more: that would make a significant difference to riding speed (for the same power).
     
    Last edited: 8 Feb 2019
  10. YukonBoy

    YukonBoy Extra solar

    Location:
    Ultima Thule
    Assuming it is the same rider and that the 170lb version got there through losing fat and getting fitter. The lighter rider will have a super power output and VO2max compared to their fat self. So lose the weight or get an e bike.
     
  11. OP
    OP
    12boy

    12boy Über Member

    Location:
    Casper WY USA
    I thank you all for your responses. I gather now that weight isn't as big a factor as aerodynamics. The weight of wheels is most critical with hills and acceleration, not maintaining speed. That is probably also true for both heavy rider/light bike or light rider/heavy bike. I am thinking my takeaway is a pound or so on the bike or on me doesn't matter unless my ride is stop and go or a lot of climbing. To really get to the original issue I probably would have to add some weigh to one of my bikes, see how fast I could go for a given ride, take the weight off off the bike and stuff my pockets or put it in a pack and time that ride too. If a pound or so isn't really important a lot of money is being spent paring down the weight. I have always noticed my riding slows down in the winter. Perhaps the extra pounds of clothing aren't as critical as my larger size, due to clothing, and the fact cold air is significantly denser than warm air.
     
  12. raleighnut

    raleighnut Guru

    Location:
    On 3 Wheels
    This,

    DSCN0058.JPG

    Goes faster uphill than this,

    DSCN0207.JPG

    does

    However the Saracen will climb steeper hills easily (bottom gear is 22 front 26 rear)
     
  13. Yellow Saddle

    Yellow Saddle Veteran

    Location:
    Loch side.
    Your summary of all the above comments is wrong.

    Weight is a big factor when climbing. And since wheel weight is a fraction of body weight, the latter is where all the concern is. When climbing, a heavy person has to overcome gravity. When racing on the flats, a heavy person has to overcome aero drag. But because human shape can be approximated as a cylinder, things aren't all that obvious. Lets assume a person is heavier because they are a bodybuilder and has plenty of muscle. Because we are cylinders our muscle ratio increases by the radius of your torso squared. V= πrsquared times height. But, at the same time, the frontal area (whichcauses aero drag) only increases by a factor of one. In other words, someone strong with a frontal area of 2, has a muscle volume of 4. But a weakling with a frontal area of 1, only has a muscle volume of 1. You can see that the bodybuilder will kill the weakling on the flats where they only have to overcome aero drag.
    However, on the climbs, the weakling only has to drag a weight of 1 up the hill whilst Arnoldonabike has to drag 4 up the hill. Here the weakling excels.
    Important to note that wheel weight is a tiny, tiny, tiny fraction of that overall weight that has to be dragged up the hill and therefore makes NO SIGNIFICANT difference. Same for accelleration. The entire unit of man-and-machine has to be accellerated, not just the wheel, so a heavier wheel is again, insignificant.


    I've armed you with the method of calculating whether your statements above are true or not. No need to fiddle with inaccurate experiments where you can't control the variables.
     
  14. Drago

    Drago Guru

    Arnold on a bike isnt such a good example. Arnold has more to tow, but a disproportiomately high level of muscle mass with which to do so. The numbers start to skew a little when you look at those with higher muscle mass than simply lard-O's, because while the beefcakes have extra mass a greater proportion of that extra mass is itself available to do work, and not simply a passive passenger. I'm not a fast rider simply because my aero is all wrong and I've never trained to be specifically quick jn any cycling discipline, but a number of supposedly accomplished club competitors have had to eat their words after riding North Wales with me.
     
    MrBeanz likes this.
  15. Yellow Saddle

    Yellow Saddle Veteran

    Location:
    Loch side.
    That was my point. The opposite is obvious.
     
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