Does weight really matter

Discussion in 'Cycling Equipment' started by bladegeek, Oct 3, 2006.

  1. Rhubarb

    Rhubarb New Member

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    Yeah it is a big drop, probably an exaggerated example for most people trying to get some weight of their bikes but none the less I certainly can vouch for weight making a difference. I think though it has to be somewhat substantial unless of course you are at the elite level where it all counts.

    And your right about the responsiveness, its awesome in comparison. It just goes!
     


  2. PartisanRanger

    PartisanRanger New Member

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    Ha, congrats. Must have sucked not being able to ride for so long... Better get yourself training for racing season though, PartisanRanger is gonna tear up the C's! :p
     
  3. 531Aussie

    531Aussie Well-Known Member

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    this is my anecdote:

    I'm no weight weeny -- my lightest bike is probably 8.5kg -- and I prefer strong, stiff stuff over light, floppy stuff, especially wheels.

    I notice a difference in "feel" when the weight difference of the bike is approach 2kg (in other words, my old 531 bikes feel slower than my lighter alu bikes) but I can't honestly say this translates to a 'real speed' difference on flat or rolling roads
     
  4. sogood

    sogood New Member

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    But still, it's an area that's easier to shave a significant amount of weight. Recently I managed to trim off around 600g in a combined wheel and tyre change, along with improved bearing (reduced frictional resistance). Now I have two sets of wheels for different purposes and neither is put to waste.
     
  5. alienator

    alienator Well-Known Member

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    Yup, you're right. If a person wants to shave weight off his bike, the first place to go is the wheels because that's where the biggest gains....er, weight losses.....are. In my recent wheel history, I went from Bontrager Race X Lites (veritable crap wheels) to a custom set with White Ind's new hubs, CX Ray spokes, and Alex Crostini 3.1/3.2 rims. In the process, I shaved about 250g off the bike weight. Then I bought a set of Reynolds Stratus DV tubies and shaved another 120g off. So in total, I lost 0.8 lbs. The only real performance difference that I notice is that once the pace gets goin' I can maintain a slightly higher speed w/ the Stratus DV's. Of course, that's an aero thing, not a weight thing.

    The one place everyone notices weight loss on a bike is when they're climbing out of the saddle or sprinting. In both cases, you can feel the difference as you throw the bike back and forth. Of course, that means squat for goin' faster.

    There's naught wrong with wanting to shave weight off the bike. I'm a gearhead/tech geek, and making my bike lighter while keeping it everyday useable was/is fun in a weird way. It's important though to keep in mind that any performance gains from dropping your bike's weight will be very small, at best.
     
  6. sogood

    sogood New Member

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    Not sure the basis of perceived improvement, but after I changed the wheel, I definitely felt the bike is more lively on acceleration. It could be the weight reduction, it could also be the stiffer wheel. At the end of the day, it's good to be able to perceive an improvement in the bike after all the expenditure. As to whether it's scientific or not, that's for another day. :D
     
  7. 531Aussie

    531Aussie Well-Known Member

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    rotational mass is a bit of a myth.

    "dominant factor in wheel performance is aerodynamics. Wheel mass is a second order effect (nearly 10 times less significant) and wheel inertia is a third order effect (nearly 100 times less significant). http://www.biketechreview.com/archive/wheel_theory.htm

    fast wheels are those that are rigid and aero, like these: :)
    [​IMG]

    1250g for one wheel!!!!

    and let's not forget the heavy track bikes that are stiff and aero, weigh 18 to 20 pounds, yet have to be accelerated from 0 to 60kph as quickly as possible!
    None of the bikes at the recent Track World Champs came close to the UCI's minimum weight of 6.8kg
    http://www.cyclingnews.com/track/2006/apr06/wtc06/tech/?id=/tech/2006/features/track_worlds_bikes


    If a lighter wheels flexes more, then it is slower in all situations, with the exception of big mountains. Some light wheels flex so much that they rub on the brakes!! Brake-rubbing aren't very fast! :)

    as far as weight on hills goes, isn't it simple physics?
    I guess the point is how much weight will be noticeable.

    As far as accelerating a mass a flat ground goes, I guess that's slightly less simple physics. :) Then I suppose there's a difference between accelerating from zero kph to a given speed, or from (say) 30kph to a given speed.


    there's a well known coach around here who puts weighted vets on his athletes to let them feel how much a few kg of blubber slows them down.
     
  8. bobbyOCR

    bobbyOCR New Member

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    Weight does matter. But only if it is lost in the right places. If you get a lighter frame which is much flexier than your old one (or wheels for that matter) alot of power will be lost making them flex, so even though it is lighter, you lose speed on a hill or in a sprint where it really matters. Also, if you get a light bike (i know this is negligible) which isn't aero, it will be harder to maintain a speed in real world conditions. If you want to lose weight where it matters, get lighter shoes or a tyre/tube set. I count the weight of my shoes when i am weighing my bike out of curiosity, as I believe they are a part of it, as it is very very difficult to ride without them on. I lost 300g from the shoes, 60g from the pedals, 130g from tyres/tubes for only $430, plus gaining stiffness and losing rolling resistance. That is the best value.
     
  9. Strid

    Strid New Member

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    I know, don't pick on me too much! I seriously messed up friction by a factor of v there ... :D


    Anyway, you seem to be right, the approximation that a small percentage decrease in weight equals the same percentage increase in climbing speed is really good.
     
  10. vadiver

    vadiver New Member

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    So out of all of the discussions of physics and flex and such.


    The way to loose the most weight and thus gain the most speed is jaw surgery?

    My copay on the surgury would be $125. Loose 23 pounds.
    Upgrade bike $400. Loose 12 ounces.
     
  11. ScienceIsCool

    ScienceIsCool New Member

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    +1 for Alienator
     
  12. bladegeek

    bladegeek New Member

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    Having started this thread.....the bottom line is if you want to be a better climber have jaw surgery. :D LMAO!
     
  13. allgoo19

    allgoo19 New Member

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    Or get chemotherapy.
    I know one guy swear that was the best thing happened to him. He's pretty famous too.
     
  14. anth

    anth New Member

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    I think there is too much variation for there to be a typical power requirement but this page should give you something to work with. For the same cyclist and conditions it gives a range between 75 and 622 watts depending on the type of bike and body position.
     
  15. 531Aussie

    531Aussie Well-Known Member

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    I've gotta get this off my chest :)

    I blame triathletes for introducing all this 'weight weeny' stuff. When i was racing in the late '80s, apart from the odd mention of Tour riders drilling out components for mountain stages, most of the chat about good equipment centered around stiffness, never weight. It was 'stiff this' and 'stiff that', or the 'smoothest and fastest hubs'. We even tied and soldered out wheels for more stiffness (I dunno if it worked). Then the flower pot heads came along (triathletes were smart enough to wear helmets before we did :)), and they were the first dudes I heard obsessing about bike weight.
     
  16. bobbyOCR

    bobbyOCR New Member

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    I put stiffness and durability long before weight. I'd rather have a stiff, well fitting traditional geometry frame, than a cheap, ill fitting compact carbon thing that weighs 400g less. I could lose that 400g in a week with a little effort.
     
  17. geo8rge

    geo8rge New Member

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    If you want to test it try this:
    1) Get a heart rate monitor.
    2) Do a hill course for 1 hr keeping your heart rate constant.
    3) Record how far you got

    4) Repeat 1 to 3 above with a weight on your bike.

    Compare the results. The theory is heart rate is a proxy for energy consumption.

    BTW, the extra 10lb probably means little if you already weigh alot say over 200lb. In that case spend the extra money on hubs/BB/tires/rims.
     
  18. 531Aussie

    531Aussie Well-Known Member

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    yeah, that's why Columbus starting taking over Relynolds in the lates 80s, because riders wanted the stiffness of SLX and MAX, etc; even though this stuff was usually heavier than 531
     
  19. ScienceIsCool

    ScienceIsCool New Member

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    Sounds kind of complicated. I'd trust the math... F = ma, E = Fd, and P = E/t. In other words, it takes x% more force to accelerate x% more mass. It takes x% more energy to lift x% more mass up a hill. And if your power output doesn't change, it'll take you x% less time to climb a hill.

    Just remember that the mass (and change of mass) is for the whole system which includes you, your bike, the water bottles, the clothes you're wearing, etc, etc.

    All this neglects air resistance of course, but it is much, much better than an order of magnitude calculation and way more accurate than that heart rate thingy.

    John Swanson
    www.bikephysics.com
     
  20. bobbyOCR

    bobbyOCR New Member

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    +1

    Measuring heart rate with that method has way too many uncontrollable veriables which render the results inaccurate. The maths is more accurate,
     
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