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  1. #1
    GOT ME A 29ER!!!
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    Body Weight Vs. Bike Weight

    I've looked around a bit but can't find this question in another thread, though I may have missed it.

    If you lose 4 pounds of fat from your body and ride the same bike, does it feel the same for riding as not losing any weight and buying a bike that weighs 4 pounds less?

  2. #2
    Don't be hasty.
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    Absolutely not. Regardless of losing important rotating weight etc. Just think of the loss percentage, if you're 185 lbs and you lose 4 lbs, thats only a 2.1% difference. If you lose 4 lbs off a 29 lb bike, thats almost a 14% difference.

  3. #3
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    When you are climbing a hill it is the weight of yourself+gear+bike resisting you + a little resistance from friction so wouldn't an equal weight loss from either part make it the same amount of energy used? This is just the way I understand it although I guess I must be wrong as no one else thinks so.

  4. #4
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    You are correct.
    You have to move both the body and bike as a unit.
    Weenies will argue endlessly....but you can't separate the two.
    Although a lighter bike does feel better under you.....

  5. #5
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    Punch numbers in here and see what it says. The possibilities are endless.....


    http://www.mne.psu.edu/lamancusa/Pro.../bikecalc1.htm
    Gravity doesn't pull....it sucks!

  6. #6
    GOT ME A 29ER!!!
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    That calculator uses counts bike weight and body weight as equal pound for pound. If you put in any 2 sets of 2 numbers that add up to the same number and leave all other variables equal, the required power input will stay the same.


    (bike=100 + rider=100, bike=1 + rider=199 and bike=199 + rider=1 all have the same required power inputs)

    I guess you can feel the difference between 2 different weighted bikes because the change is instant, while a change in your weight would happen over time and you would forget what it was like to ride with a heavier body.

  7. #7
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    You can't treat bike weight and body weight the same. Of course its a good idea to trim weight off both but what a bunch of people fail to understand is that the bike is an object outside of your body that you are continuously ACCELERATING around, particularly riding off-road. Every time you accelerate something you need more force to accelerate something heavier. The "acceleration" I'm talking about is not just speeding up and slowing down in speed, its stuff like lifting the front end of the bike over rocks and logs. Moving the bike from side to side in and out of corners. Also, everytime you push on the pedals you are accelerating. Just to maintain a constant speed (which you never do anyway) in the real world you are continuously accelerating and decellerating.

    Here's an example, how many times do you think you can lift a 5kg dumbell compared to a 3kg dumbell? When lifting that dumbell (the front of your bike) it doesn't matter what your body weight is, but I bet the lighter the bike the more times you can do it before getting tired.

    Loose weight everywhere, but loosing weight off the bike can make a bigger difference that off your body. Of course, heaps of people can loose much MORE weight off their body so that's a good and cheap place to start.

  8. #8
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    Last year I rode a 32 pound full suspension bike, this year i`m riding a 20 pound hardtail. My first ride up a normal trail yesterday was 30 minutes faster than my best time last fall. The light bike has a massively different feel over the FS with lockout. I also weigh about 12 pounds more than I did last fall.

  9. #9
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    Shouldn't the drastic difference in weight feel caused by the sudden reduction of weight from the bike (before and after parts change) compared to a gradual reduction in weight from the rider?

  10. #10
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    Quote Originally Posted by Kaizer
    Shouldn't the drastic difference in weight feel caused by the sudden reduction of weight from the bike (before and after parts change) compared to a gradual reduction in weight from the rider?
    Yes, that is what i was trying to say

  11. #11
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    TigWorld, your point about lifting the front over obstacles makes sense but what about if you were climbing a smooth plain? Then body weight and bike weight wouold be equal as far as resisting your pedaling efforts, right?

  12. #12
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    Quote Originally Posted by elcoolio1
    TigWorld, your point about lifting the front over obstacles makes sense but what about if you were climbing a smooth plain? Then body weight and bike weight wouold be equal as far as resisting your pedaling efforts, right?
    In theory yes, but if you were to look really closely at your speed it would be continuously increasing with each power pulse from each leg and decreasing as you pedal through the "dead zone". The effect each time is minor but happens thousands of times on the average ride.

    Same principles apply to rotational weight (ie. your wheels) where the added weight is even more pronounced because the outside of a rotating object is continuously accelerating even at constant speed.

  13. #13
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    Quote Originally Posted by TigWorld
    You can't treat bike weight and body weight the same. Of course its a good idea to trim weight off both but what a bunch of people fail to understand is that the bike is an object outside of your body that you are continuously ACCELERATING around, particularly riding off-road. Every time you accelerate something you need more force to accelerate something heavier. The "acceleration" I'm talking about is not just speeding up and slowing down in speed, its stuff like lifting the front end of the bike over rocks and logs. Moving the bike from side to side in and out of corners. Also, everytime you push on the pedals you are accelerating. Just to maintain a constant speed (which you never do anyway) in the real world you are continuously accelerating and decellerating.

    Here's an example, how many times do you think you can lift a 5kg dumbell compared to a 3kg dumbell? When lifting that dumbell (the front of your bike) it doesn't matter what your body weight is, but I bet the lighter the bike the more times you can do it before getting tired.

    Loose weight everywhere, but loosing weight off the bike can make a bigger difference that off your body. Of course, heaps of people can loose much MORE weight off their body so that's a good and cheap place to start.
    Finally some sanity on this subject. I am fully with you!
    I have always subscribed to this. If you are 130lbs or 200lbs at the same weight a lighter bike will always be better to handle and climb. It is all in how high and many are the hills, accelerations and such. Saving 500grams off a bike is a big deal - regardless of your weight. Losing weight is likely a good idea for most of us as well....

  14. #14
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    Pedaling up and down hills, starting from a stop, you're always accelerating the bike and your body. Jumping you always have to get the bike and your body moving. If your body is heavier it's harder to get started, but you have more momentum to lift the bike, and vica versa.

    From an external view of the system I don't see the difference. Internal to the system, If your body is heavier you have to support your body and pedal the bike. Therefore I think that the rider being heavier will take more of a toll, even though the output would be the same. On the other hand If the rider is heavier he gets more force by gravity.

    I don't see any difference. No scientific proof, just my opinion. From strictly a personal point of view I like a lighter bike. I've ridden a bike that 5lbs heavier, and noticed a lot. I've gained 5lbs, and didn't notice at all.

    Never the less, I'm losing weight, and trying to lighten the bike under the premise that neither one will slow me down.
    Gravity doesn't pull....it sucks!

  15. #15
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    When a 200 pound person climbs a hill he uses more energy than a 150 person but also stores up more potential energy for coming down. I get the feeling that I am wrong but I can't quite understand it any other way.

  16. #16
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    Losing weight from both bike and body is important, but from a strictly performance point of view, you'll gain more advantage losing 4 lbs from your bike than 4 lbs from your body.
    Especially if you are losing weight from the wheels and drivetrain. Every single pedal stroke is a micro acceleration. The obvious solution is to try and remove weight from both bike and body, for the biggest benefit.

  17. #17
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    This may be off subject, but I'm seeing the account for fitness level. Your body and your bike can weigh the same, but as you increasing strength and endurance over time, everything about your ride will change. From speed to how you "handle" the bike.

    This comes from experience......over the past two months I've been training for a 6-hour race. My bike and I weigh the same, but I'm continually riding faster and longer....breaking records everytime I go out. Sure I'd love to carve 2-4 pounds off my steed, but "free" progress is being made and it's more gratifying.

  18. #18
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    You guys are all over the map.You have total weight(you and bike weight) and sprung and un sprung weight.(you 170lbs bike 30lbs.) On an even surface you would not notice much...given the same fitness/strenght level as if you weighed 199 and the bike weighed 1 pound.But once you start bouncing that bike around the inertia of the bike takes alot more energy to control..Lighter bike better...lower body fat better

  19. #19
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    you can have up to 13 pounds of sh*t in you, could this make a considerable difference in a race?

  20. #20
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    It is really pretty simply. You can all try this right now - what ever your weight. Take a weight, any weight. No see how many times you can lift it until you can't. Now if you had taken a heavier weight I bet ten trillion dollars you couldn't have lifted it more and you would have lifted it less times. Even if a few grams different and you are 200lbs.

    Now if you were stronger you might. But its not about that.

    But as a few have articulated here. Body weight is different from bike weight. Losing 500g off a bike is worth far more and is far different than losing body weight.

    You're not your bike!!!

    Stop trying to combine the two. Its just silly. Of course a lighter person might overcome gravity more easily given the same strength. But that same person will benefit from just a few grams lighter bike at any time.

    Lighter is not better when it breaks.

    All IMO of course.

  21. #21
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    Quote Originally Posted by Coldass
    It is really pretty simply. You can all try this right now - what ever your weight. Take a weight, any weight. No see how many times you can lift it until you can't. Now if you had taken a heavier weight I bet ten trillion dollars you couldn't have lifted it more and you would have lifted it less times. Even if a few grams different and you are 200lbs...
    Spot on.

  22. #22
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    Both are correct. You will feel the difference in a lighter bike almost immediately. On the body however, it happens over time. What most people don't think about is the process of losing weight. It takes time to shed the lbs off the body. During that time, your are probably exercising and eating a cleaner diet. Both of which will help to promote your fitness level. Losing the extra body weight will inturn decrease how hard your internal organs have to work to support the rest of the body, ie 02 consumption, blood pressure, v02 max...The result is a better functioning body. But everyone is different and while my body may work best at say 178 lbs someone else might have an optimum weight of about 136!

    I do agree, that yes, the bike and body together need to make it up the hill but if you were to loose 4-8 lbs off the body, I bet you would be better fit physically, and it would make the climb up said hill that much easier. But yes, you will still feel the difference of the lighter bike first and foremost.

  23. #23
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    This thread is hilarious! You know I have to "Micro-Accelerate" my head up hills all the time. Now I could lose about 20lbs of weight that is just sitting there...
    Last edited by ChainChain; 03-09-2011 at 10:11 AM.

  24. #24
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    Keep in mind that body weight is not dead weight: it's alive, and requires care and feeding. Additional food, water, and air is required to keep those cells alive in addition to what is required to carry them around with you. When you lose it, you have a bit more energy to spend on your muscles.

  25. #25
    GOT ME A 29ER!!!
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    so is it better to carry a water bottle in a backpack/use a camelbak than mount your water on your bike? If it is in a bottle holder it is essentially part of the frame for weight. You could potentially lose 2 kg from your bike if you were carrying two 1 litre bottles in holders on your frame and moved them to a backpack.

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