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  1. #1
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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
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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
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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 11:11 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
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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.

  26. #26
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    Quote Originally Posted by @dam
    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.
    That may sound correct, but its not. There's too many variables involved when you use the term "body weight".
    A competitive Protour rider will always ride a bike that is the minimum weight allowed to ride up a smooth road. Regardless if they weigh 120 lbs, or 170 lbs. If they were allowed to ride a 12 lb. bike, they would all be riding one at that weight to go up any mountain climb.

  27. #27
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    Quote Originally Posted by elcoolio1
    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.
    You'll find a lot of personal preference answers to that one, but moving that weight to your back makes it easier to carry. Some would argue that its better to have that weight mounted low on the bike, but that puts the weight farther away from your body, and requires more leverage to move it around. For example, lifting your bike over log crossings, or bunny-hopping is easier with the water on your back. On a road bike, it doesn't have as much benefit, and its probably better to have the water weight on the bike.

  28. #28
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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.

    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.
    Are you talking about curling dumbbells or what? If you think about doing squats (somewhat comparable to pedaling a bike) and then adding even 15 or 20 lbs to the bar (external weight, like adding it to your bike), I bet you would notice the difference just as much as you would if you put on a 15 or 20 lb weight vest instead (like gaining weight on your body). All I'm saying is that the weight of your bike and the weight of your engine are not totally disconnected.
    However, If you tried running through an obstacle course or something with 5lb weights in each hand and then did it with a 10lb vest on, I'm sure the vest would feel much less noticeable.
    Idk, I can see the argument for both sides

  29. #29
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    http://en.wikipedia.org/wiki/Power_(physics)
    http://en.wikipedia.org/wiki/Mechanical_work

    the formula for mechanical work has mass in it, more mass = more work done. 1/2M(V2-V1)

    also power is a time function (W/T) so if work is related to mass then the power exerted also is.

    but more mass gets more Pe
    http://en.wikipedia.org/wiki/Potential_energy

    the world takes place with acceleration if you blink you accelerated if you read this you accelerated. you can never be still.
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  30. #30
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    Quote Originally Posted by turbogrover
    That may sound correct, but its not. There's too many variables involved when you use the term "body weight".
    A competitive Protour rider will always ride a bike that is the minimum weight allowed to ride up a smooth road. Regardless if they weigh 120 lbs, or 170 lbs. If they were allowed to ride a 12 lb. bike, they would all be riding one at that weight to go up any mountain climb.
    I don't follow. Cells require oxygen and energy to maintain life, do they not? It has nothing to do with light bikes being preferable to heavy bikes. I'm just saying weight on the body has an additional cost beyond the obvious cost of having to work harder to accelerate that weight.

    No idea where the pro tour rider thing you bring up comes in. All those guys barely have any body fat to start with, so they couldn't lose much body weight if they wanted to.

  31. #31
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    Quote Originally Posted by @dam
    I don't follow. Cells require oxygen and energy to maintain life, do they not? It has nothing to do with light bikes being preferable to heavy bikes. I'm just saying weight on the body has an additional cost beyond the obvious cost of having to work harder to accelerate that weight.

    No idea where the pro tour rider thing you bring up comes in. All those guys barely have any body fat to start with, so they couldn't lose much body weight if they wanted to.
    Okay, even if you're a 200 lb rider, losing four lbs off the bike will make you faster than losing four lbs of fat off the body. Sound better?

  32. #32
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    Quote Originally Posted by turbogrover
    Okay, even if you're a 200 lb rider, losing four lbs off the bike will make you faster than losing four lbs of fat off the body. Sound better?
    Nevertheless, your bike doesn't metabolize O2 and energy to stay alive.

  33. #33
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    The other benefit from losing weight on your body is usually your increase in fitness. If you got rid of 20 lbs by liposuction it might not be noticeable riding, but if you lose 20 lbs by eating better, running, and playing basketball you are going to do a lot better. Not that it would be better than going from a 45 lb downhill bike to a 25 lb xc bike.

    One advantage to a lighter bike comes from the increased agility and handling rather than just the effort, and this improves your skill as a rider. When riding dirt bikes, I had a 320 lb dual sport that I hated, and switched to a 220 lb mx bike for trails. I rode it for about 6 months and then switched back to the big bike and loved it. It was so much easier to ride than it used to be because of my increased skill from the lighter bike transferring back.

    If you ride a big downhill sled and then spend some time on a lightweight nimble xc bike on twisting trails, I guarantee when you go back to downhill you will see how much better control you have and choosing lines, etc, you won't be thinking how heavy your bike is until you are going uphill.

  34. #34
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    Here is my take on it. I am not a kinesiology scientist but just what I have learned over the 25 years of riding. I think what affects speed is the weight and strength ratio in relation to bike weight. Just being lighter in body weight doesn't necessarily mean you will be faster. Strength needs to be same or greater to be faster. Having longer legs helps because it allows for better leverage and less energy. Also, a lighter bike and better pedaling geometry will make a difference in being faster. Obviously lighter bike is easier pedaling and geometry helps because of the better leverage you have in relation to gravity. I feel the main things to focus to be faster is lighter, stronger, lighter bike, and better geometry.

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    Quote Originally Posted by Coldass View Post
    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.
    Just reading this forum for the first time. Not sure I agree with the dumb bell argument. When biking you are moving you entire body weight, however when curling a weight for example you are only using your arm. Therefore, comparing a 130lb and 200lb person isn't fair. You should be comparing a 10lb arm vs a 15lb arm. And I would think the 15;b arm could curl more weight.

  36. #36
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    I think an interesting study would compare similar bikes (with the same wheels) and in one case a five pound heavier frame (or parts) vs adding a five pound weight vest to the rider. This would eliminate the rider's fitness from the equation, but the human variable still exists.

  37. #37
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    Quote Originally Posted by turbogrover View Post
    For example, lifting your bike over log crossings, or bunny-hopping is easier with the water on your back. On a road bike, it doesn't have as much benefit, and its probably better to have the water weight on the bike.
    Right on! It all depends on how you manage where the weights are distributed depending on your riding style and capability. Downgrading my bike by 1kg has made me a non-jumping muted rider but a much faster one on descends due to bike stability.
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  38. #38
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    Quote Originally Posted by aliikane View Post
    Here is my take on it. I am not a kinesiology scientist but just what I have learned over the 25 years of riding. I think what affects speed is the weight and strength ratio in relation to bike weight. Just being lighter in body weight doesn't necessarily mean you will be faster. Strength needs to be same or greater to be faster.
    Which is why whenever my much heavier buddy loses an uphill climb and complains about me being a lot slimmer I think it's load of BS as the muscles in his thigh is more than both of mine combined.
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    How Lightweight Do You NEED Your Bike To Be?

    that article would seem to suggest that the lighter bike if not significantly lighter doesn't mean much to most of us weekend warriors...

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    Don't forget the mental aspect of it to.
    The worst is feeling the highest of highs, but always feeling the lowest of the lows.

    It's all a dream...

  41. #41
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    Quote Originally Posted by dogshine View Post
    How Lightweight Do You NEED Your Bike To Be?

    that article would seem to suggest that the lighter bike if not significantly lighter doesn't mean much to most of us weekend warriors...
    Increasing my bike by 1kg by "downgrading" to Deore 10 speed 2012 from X-0 9 speed and replacing the 1580gr wheelset with the 1685gr one yields exactly the same finish times at the same track under the same condition. I have to say that's probably because I now use the largest ring (42) as opposed to the mid ring with the old X-0. What differs however, is my ability to jump and to make sharper turns. I bet if the track is more technical the result would differ quite a bit.
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    In the last month I have cut 5 pounds from my gut and added 2 pounds to the bike in the form of a suspension fork. I can tell u I am much faster now than I was a month ago. There is a little climb just shy of a mile long, about 300 vert that last month took 7:02 to get to the top, today it was 6:32. Thinking of taking the weight back off the bike though.

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    Quote Originally Posted by Veda View Post
    Which is why whenever my much heavier buddy loses an uphill climb and complains about me being a lot slimmer I think it's load of BS as the muscles in his thigh is more than both of mine combined.
    Not BS -- he may well be twice as strong as you, but remember his heart and lungs have to support the needs of those huge muscles too -- i.e. his heart would have to pump twice as much blood, and his lungs twice as much air (more complicated than that, but you get the point). That is very unlikely, unless you are very unfit.

    This is why guys that are very fast up hills (XC racers, hill climbing specialists in road racing) are invariably of a light build. Being light doesn't make you fast, but it does give you the potential to be fast, with proper training.

  44. #44
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    Quote Originally Posted by TigWorld View Post
    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.
    We all want to believe that, because it's easier to write a cheque than to exercise and/or reduce our caloric intake.

    Losing weight off the bike matters because we move the bike around. Absolutely true. All other things being equal, losing rotating weight is excellent. Does losing non-rotating weight off the bike matter more than losing weight off the body? Not in practical terms. In practice, we often stand out of the saddle to climb or move through turns. We use our core and arm muscles to hold our torso erect. Losing weight off the body means we need less energy when we stand up.

    If you weigh a lot, you are more likely to sit down most of the time. You are more likely to climb hillsbin your granny, spinning continuously. If you weigh less, you are more likely to have an active style, mixing standing and sitting, climbing many hills by rising from the saddle and applying power. But forget the "stats." if you personally weigh less, you can sit or stand as you choose. If you weigh more, you need to sit more or waste energy.

    So I think you should lose weight in both places. But I would not say that non-rotating bike mass is magically more important than body mass.

  45. #45
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    Quote Originally Posted by dogshine View Post
    How Lightweight Do You NEED Your Bike To Be?

    that article would seem to suggest that the lighter bike if not significantly lighter doesn't mean much to most of us weekend warriors...
    Yes it does. Every bike manufacturers are selling you a better suspended, lighter and stiffer bike than 5 years ago at the same price point.

    I agree with bike weight being more important than body weight and that rotating weight is more important than frame weight all other dynamic components being the same.

    I have ZTR Race, ZTR Crest and ZTR Flow wheelsets that I can switch on the same bike and I notice the impact of rotating weight instantly.

    For the weekend rider reliability it a priority and confidence in the parts we ride gets more important. I have more confidence in my Flows with Nobby Nic 2.4 SS attacking the rough stuff on the downhills AND the uphills than my Race wheels with Rons 2.25 evo. I also have a lot more grip with lower pressure and bigger knobs so I skid less and corner better. Uphill speed is less important because friends wait for each other at the top anyways.

    Most people here will agree that a dropper seatpost make a trailbike faster overall even if it adds 3/4lb.
    Last edited by trek551; 09-05-2011 at 07:26 AM.

  46. #46
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    I agree with the guys bringing strength and fitness into the equasion.
    I used to be pretty fat and ride a 40+lb bike. I managed to get the bike weight down to 32-33lb but it didn't make a huge difference in what I could do. I then started training and riding much more frequently, dropped body weight and improved fitness, and now I can go like a tank all day.
    My riding skills have improved somewhat too, probably due to riding more but I think the added fitness helps alot.
    I think people put too much emphasis on upgrading their bike when they need to focus on 'upgrading' themselves.

  47. #47
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    All I know is that bike weight makes all the difference. When my ride was 32lbs and I was 170lbs I was a lot slower than now at 195 and bike is 25.8lbs...

    I dont understand why because only some of that is rotational but bike weight makes a huge difference.

  48. #48
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    For entertainment purposes only, be sure to read the thread on water bottles:

    Water bottles on bike?

    Lots of folks arguing water bottles vs. Camelbaks are arguing the exact question of rider weight vs. bike weight, sans the question of rotating weight and physiology.

  49. #49
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    Entertainment? But we're so dead serious about performance gained from grams!
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  50. #50
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    As someone who has always had to fend off those who insist on an explanation why I like a light bike, I also have to mention the physics of the situation.

    Aside from the small accelerations of the bike under the rider, independent of the rider, unless both the bike and the rider are accelerating together, the bike or the rider would depart from each other. In other words, aside from small bike movement, when you pedal you are accelerating your body and your bike equally.

    Also, when climbing, the amount of work it takes can be calculated from F x (distance)=ma x height. Your mass (including bike) times the acceleration of gravity times the altitude gained.

    I want to separate bike from rider. But unless all of those small accelerations add up to significant amounts of work, I can't. That doesn't mean that losing weight isn't crucial.
    Note to self: 85% of FTP for 20 min.

  51. #51
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    Quote Originally Posted by Gregg K View Post
    when climbing, the amount of work it takes can be calculated from F x (distance)=ma x height. Your mass (including bike) times the acceleration of gravity times the altitude gained.
    I think this is roughly true for seated climbing. When standing, shouldnít we also consider the effort required to support the body and shift it back and forth?

  52. #52
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    If the bike is accelerating more than the body, they'd be going different speeds. In other words, your bike would be moving out from under you.

    Now as for vertical movement, that's a different situation. As you move up and down, you are accelerating your body against gravity. That is body weight only. And in as much as it contributes toward accelerating the bike, that vertical movement is perpendicular to forward/backward motion of the bike/rider. It contributes nothing toward work in the forward direction. For example, if you jump up and down on the seat of your bike, it goes nowhere. But kick the seat from behind, and the bike moves forward.

    I hate to think that bike weight isn't crucial. I just haven't been able to divorce bike and rider. Having said that, we only put out a few hundred Watts. If I take two pounds off my bike, that's good percentage of mass removed, as has been pointed out already.

    The one thing that I don't know is just how much work goes into the small movements of the bike under the rider. Even if standing, we use the bars to counter the moment of our body around the bike, as well as the force of the bike pulling us forward. We're essentially one with the bike, for all practical purposes. I wish someone would show me that I'm wrong. I'm all for being a weight weenie. When Ibis rolls out their Ripley with 26 inch wheels, I'm all over that thing.
    Note to self: 85% of FTP for 20 min.

  53. #53
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    i know whats easier for me at least, but many disagree. adding weight to my body (pack with bladder,tool,minipump,tube) rather than the attaching the same gear on my bike frame, makes technical sections, jumps, ledges, a lot easier for me.

    shedding 20lbs of body fat will not feel like youre riding a 5lb bike.

  54. #54
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    Quote Originally Posted by Gregg K View Post
    When Ibis rolls out their Ripley with 26 inch wheels, I'm all over that thing.
    Dude I was thinking about the same thing!
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  55. #55
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    Amazing new business idea for bikes

    So my buddies had this idea the other day, fill a frame with hydrogen gas, or the slightly safer but less effective Helium to save weight. We were talking about this for a while then realized, WHAT ABOUT TIRES?!?!?! It seems easy enough and cheap enough to do, fill your tires with Helium from the dollar store, save a tiny bit of rotational weight. I know it would be super small amounts of weight savings but you would think somebody would be doing it at the uber weight weenie or world cup level. Is it outlawed by UCI?

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    Quote Originally Posted by elcoolio1 View Post
    So my buddies had this idea the other day, fill a frame with hydrogen gas, or the slightly safer but less effective Helium to save weight. We were talking about this for a while then realized, WHAT ABOUT TIRES?!?!?! It seems easy enough and cheap enough to do, fill your tires with Helium from the dollar store, save a tiny bit of rotational weight. I know it would be super small amounts of weight savings but you would think somebody would be doing it at the uber weight weenie or world cup level. Is it outlawed by UCI?

    I did a quick calculation and estimate you might save 5 grams of weight if you had helium in your tire instead of air. More than I thought originally. It appears you have roughly .5 moles of gas in your tire at 45 psi. (did a lot of rounding, but that's the general idea).

    One problem is the permiability of the tire. Helium is a much smaller molecule than nitrogen or oxygen, and would travel through the rubber much more easily.

    So, it probably hasn't been done because;
    - Minimal weight savings
    - cost of helium
    - need for frequent refills.

  57. #57
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    Quote Originally Posted by smilinsteve View Post
    I did a quick calculation and estimate you might save 5 grams of weight if you had helium in your tire instead of air. More than I thought originally. It appears you have roughly .5 moles of gas in your tire at 45 psi. (did a lot of rounding, but that's the general idea).

    One problem is the permiability of the tire. Helium is a much smaller molecule than nitrogen or oxygen, and would travel through the rubber much more easily.

    So, it probably hasn't been done because;
    - Minimal weight savings
    - cost of helium
    - need for frequent refills.
    This has been discussed on MTBR before, and while there are a number of interesting issues to discuss, yours is the consensus answer: Helium and Hydrogen molecules are so small that making a tube or tubeless tire to hold them effectively would negate the weight savings.

  58. #58
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    Plus (though I'm not sure how to do the exact calculations anymore) the air in your tires takes a LONG time to actually start rotating. So the mass of the air wouldn't even be considered rotating weight.

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    Quote Originally Posted by elcoolio1 View Post
    So my buddies had this idea the other day, fill a frame with hydrogen gas, or the slightly safer but less effective Helium to save weight. We were talking about this for a while then realized, WHAT ABOUT TIRES?!?!?! It seems easy enough and cheap enough to do, fill your tires with Helium from the dollar store, save a tiny bit of rotational weight. I know it would be super small amounts of weight savings but you would think somebody would be doing it at the uber weight weenie or world cup level. Is it outlawed by UCI?
    I think a much more compelling argument could be formed for the use of nitrogen in tires as opposed to helium...

  60. #60
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    Quote Originally Posted by Ace5high View Post
    I think a much more compelling argument could be formed for the use of nitrogen in tires as opposed to helium...
    As an inert gas, you do have some lower corrosion of the tire from the inside and there is some claimed benefit for dragsters and other cars where the tires can get insanely hot. I canít personally see this being a win for bicycles.

    But yeah, itís certainly a more compelling argument than the argument for Helium :-)

  61. #61
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    Quote Originally Posted by raganwald View Post
    As an inert gas, you do have some lower corrosion of the tire from the inside and there is some claimed benefit for dragsters and other cars where the tires can get insanely hot. I canít personally see this being a win for bicycles.
    Dragsters and race cars don't use regular air in their tires so that they can consistently and accurately predict the expansion of their tires at elevated temperatures. Unless you plan on hitting a couple hundred miles per hour on your bike, it's probably not an issue, haha

  62. #62
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    Quote Originally Posted by TheNightman View Post
    Dragsters and race cars don't use regular air in their tires so that they can consistently and accurately predict the expansion of their tires at elevated temperatures. Unless you plan on hitting a couple hundred miles per hour on your bike, it's probably not an issue, haha
    Actually, many street cars have been using nitrogen in tires for many years. Tire pressures will remain more stable over time (less leakage) also nitrogen shows less pressure change with temperature swings because water vapor in air is the primary factor for pressure change due to temp.

    Makes a pretty good argument to me...

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    There's no advantage for nitrogen over air in terms of predictable expansion with heat or anything like like that. They are both ideal gases under the conditions in a tire.
    I could see the advantage to removing water, but dry air would behave the same as dry nitrogen. Nitrogen does have the advantage of no oxidative attack of the rubber. An advantage exploited by trucking fleets where a tire carcass could run for a million miles.

  64. #64
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    Quote Originally Posted by smilinsteve View Post
    There's no advantage for nitrogen over air in terms of predictable expansion with heat or anything like like that. They are both ideal gases under the conditions in a tire.
    I could see the advantage to removing water, but dry air would behave the same as dry nitrogen. Nitrogen does have the advantage of no oxidative attack of the rubber. An advantage exploited by trucking fleets where a tire carcass could run for a million miles.
    But wouldnt the same be true for car tires, Since nitrogen is less likely to penetrate through tire rubber?

    I personally have to top up my tires at least once or twice a week, but also live in a very humid and hot climate year round... I know from personal experience how well nitrogen in car tires performers, so Im almost tempted to see if it would act more stable in my bike...

  65. #65
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    Air is 78% nitrogen, draw your own conclusions.

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    Quote Originally Posted by AZ.MTNS View Post
    Air is 78% nitrogen, draw your own conclusions.
    I dont need to make up my own conclusions since its such a common practice with cars to do so. I think the conclusions we can draw are from factual information.

    78% of air may be nitrogen but thats pretty irrelevant since, whats most important, is that pure nitrogen doesn't contain the water vapor that air does.

  67. #67
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    Quote Originally Posted by Ace5high View Post
    I dont need to make up my own conclusions since its such a common practice with cars to do so. I think the conclusions we can draw are from factual information.

    78% of air may be nitrogen but thats pretty irrelevant since, whats most important, is that pure nitrogen doesn't contain the water vapor that air does.



    So, how much water vapor is in air? How much does that water vapor have an effect on the typical MTB tire?

  68. #68
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    Quote Originally Posted by AZ.MTNS View Post
    So, how much water vapor is in air? How much does that water vapor have an effect on the typical MTB tire?
    Where I live a pretty significant amount but I dont know how it effects MTB tires. I do know that its typically 95 degrees outside when I ride, My tires are filled indoors in 73 degrees, so I do expect there to be a pressure change given the high temp swing.

    And If that if its a significant enough effect for auto manufacturers to use in car tires, couldnt it possibly mean less top up's or less temperature fluctuation in MTB tires also?

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    Quote Originally Posted by Ace5high View Post
    I think a much more compelling argument could be formed for the use of nitrogen in tires as opposed to helium...


    Why go thru the trouble? Most quality compressed air systems include a dryer, anyone paying for nitrogen for mtb tires has more money than brains IMHO.

  70. #70
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    Quote Originally Posted by roadie scum View Post
    Why go thru the trouble? Most quality compressed air systems include a dryer, anyone paying for nitrogen for mtb tires has more money than brains IMHO.
    Well, we are all totally off topic anyway at this point. The post that started it was regarding the use of hydrogen or helium in MTB bikes.... It was just my response to that post that nitrogen was a better idea, but wasnt suggesting anyone needed to start doing it...

  71. #71
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    Hilarious, a bunch of fat asses trying to justify their overpriced bike.
    "Do not touch the trim"

  72. #72
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    Quote Originally Posted by Rivet View Post
    Hilarious, a bunch of fat asses trying to justify their overpriced bike.
    Thats your response to "Body Weight Vs. Bike Weight"?

    You make no sense.

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    Quote Originally Posted by Rivet View Post
    Hilarious, a bunch of fat asses trying to justify their overpriced bike.
    There is a kernel of wisdom in what you might be saying, but it is hard to appreciate it when it is conveyed with such an abusive tone. We humans want to believe that things that are easy--like writing a cheque for a more expensive, lighter bike--is as effective or even more effective than things that are hard--like training more and/or losing weight.

    And given that we want to believe these things, we often argue for their truth in the hopes hat if we can convince others, we convince ourselves. But even if we "win at the interwebs," that doesn't change the laws of physics. It could be that losing body weight is far more important than losing bike weight, and no amount of strident arguing here will change that.

    Then again, it could be that bike weight DOES matter more. The fact that some people here might have a self-interest in arguing that body weight doesn't matter doesn't mean they're wrong.

    The truth is in the physics and kinetics, not the shapes and attitudes of the people arguing the subject.

  74. #74
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    Quote Originally Posted by raganwald View Post
    There is a kernel of wisdom in what you might be saying, but it is hard to appreciate it when it is conveyed with such an abusive tone. We humans want to believe that things that are easy--like writing a cheque for a more expensive, lighter bike--is as effective or even more effective than things that are hard--like training more and/or losing weight.

    And given that we want to believe these things, we often argue for their truth in the hopes hat if we can convince others, we convince ourselves. But even if we "win at the interwebs," that doesn't change the laws of physics. It could be that losing body weight is far more important than losing bike weight, and no amount of strident arguing here will change that.

    Then again, it could be that bike weight DOES matter more. The fact that some people here might have a self-interest in arguing that body weight doesn't matter doesn't mean they're wrong.

    The truth is in the physics and kinetics, not the shapes and attitudes of the people arguing the subject.

    The only reason I dont exactly agree with your assessment, and more importantly Rivet is an idiot is because this assumes we have body weight to loose, or at least way more than bike weight.

    Rivet - Lets assume for a minute that there was a guy/guys who were not only in better shape then you but made you look like an out of shape 12 year old girl by comparison. That person or persons were following this thread and posting does that mean there is still no justification for trying to lighten their bike as opposed to themselves?

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    Doesn't matter where you lose it, bike or yourself as your always powering both at the same time, you get a small difference from rotating stuff think 5% definately not the 3x's people band around.

    Handling wise, a lighter bike will feel livelier, but ofcourse this isn't always a good thing as a heavy bike will be more stable.

  76. #76
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    Quote Originally Posted by gatorgrizz27 View Post
    The other benefit from losing weight on your body is usually your increase in fitness. If you got rid of 20 lbs by liposuction it might not be noticeable riding, but if you lose 20 lbs by eating better, running, and playing basketball you are going to do a lot better. Not that it would be better than going from a 45 lb downhill bike to a 25 lb xc bike.

    Actually, from a metabolic point of view if you just magically lost 20lbs (liposuction ect) you would have a measurable effect. Your body would have less cells to supply nutrition and O2 to. As well your cardivascular system (heart and lungs) would work less. As well as the loss of the weight.
    Lets not even get into a 20 lbs reduction would provide a smaller drag coefficent....

    As for this whold discussion, get a mechanical engineer to chime in.......I have my 2 cents...


    There are 2 main issues. 1 rotational bike mass vs non rotational. The effects on power are different. Rotational mass only has an effect accelerating, once at speed the effects are friction. Riding up a hill, the weight is negated by the rear half of the wheel on it's downward path. You are comparing apples and mango`s if you are looking at rotational and non-rotaional effects. They only play in in acceleration.


    I look at it this way. If you were 150 plus a 20lb bike on a set of rollers, or you were 155 on a 15 lb bike everything is the same (weight wise). You can argue, body form and riding and style but those are like voting on a figure skater, all open to interpretation.

    Hard numbers folks. No this feels, this feels.

    IMO

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  77. #77
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    Quote Originally Posted by KINBOY View Post
    There are 2 main issues. 1 rotational bike mass vs non rotational. The effects on power are different. Rotational mass only has an effect accelerating, once at speed the effects are friction. Riding up a hill, the weight is negated by the rear half of the wheel on it's downward path. You are comparing apples and mango`s if you are looking at rotational and non-rotaional effects. They only play in in acceleration.


    I look at it this way. If you were 150 plus a 20lb bike on a set of rollers, or you were 155 on a 15 lb bike everything is the same (weight wise).
    The trouble with arguing about rollers is that riding rollers is entirely unlike the kind of riding I do on a mountain bike. On a mountain bike, although I try to conserve momentum, I am actually accelerating and decelerating constantly to handle hills and turns. If I'm not accelerating on a ride, I'm bored and I won't be riding that trail again.

    I have a feeling most people here accelerate a fair bit.

    The other issue, which I raised above, is standing and especially standing while pedaling, e.g. climbing out of the saddle or standing to negotiate technical features. I may be in a minority, but I have a dropper post and I stand most of every ride. I stand to pump over berms and through sinuous single track. I stand to climb, I stand to descend. I stand to negotiate ride-overs. I stand to ride skinnies.

    I don't know how much effort it takes to carry an extra four pounds when standing, but the post that started the thread asked whether it would be better to lighten the bike or rider by four pounds. Four fewer pounds on me when standing would be sweet. More sweet than four fewer pounds of bike when hopping it over a log? Not sure. But it does seem like there is a factor that is not being taken into consideration when drawing an analogy to riding rollers.

    JM2C,YMMV!

  78. #78
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    The difference in acceleration is minimal though, think a 200lb bike + person, if you gain 4lb's from anywhere then on a completely flat surface you will need 2% more power or accelerate 2% slower, once upto speed not an issue.

    While climbing your constantly fighting gravity so it's constantly 2% more mass you have to haul up the hill.


    You could argue if you gained 4lb's a fat, then you've got bigger energy reserves ofcourse as it's fat which gives you more energy potential.

  79. #79
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    A couple of things about acceleration:
    - Don't forget about the acceleration of gravity. Weight matters when you accelerate, which doesn't just mean when you are speeding up. When you are fighting gravity, weight matters (where ever it is).

    - When you are riding on rough terrain, your bike is slowing down with every impact of the tire to the ground irregularies, and your legs fight to regain the speed that was lost. So, even though weight only matters during acceleration, that could mean it matters the vast majority of the time you are riding, even if those accelarations are small.

    - Again, riding on rough terrain, there is a lot of side to side motion of the bike, which is acceleration and decelleration perpendicular to your line of travel. That back and forth motion, happening hundreds of times during a ride, could add up to have a noticeable impact on your energy expenditure.

    Of those 3 things, only the third implies a difference between bike weight and body weight. People really seem to feel a difference with light bikes, so maybe that's part of the explanation for that, along with rotating weight, of course.

  80. #80
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    Looking at the split times between my carbon hardtail and my FR bike on the same undulating section of singletrack, I'm seeing a direction relationship between the weight of the total system and the speed.

    That is, the heavy bike makes the bike-rider combo 15% heavier and 13% slower. I'm probably pulling back that extra 2% by going downhill faster with the suspension etc.

    This means I am seeing only 13% slower times on a bike that weighs twice as much.

    Now it's my opinion that the section of trail, while steep and narrow, is not rough enough to give a real advantage to full suspension, except on the downhills, but I guess I could be mistaken(?)
    The above statements have not been evaluated by the Food and Drug Administration

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    Lighter is more fun

    I have spent many hours trying to explain to friends how my 25lbs mountain bike is much more FUN to ride than a 29 lbs bike. I like bunny hopping, jumping and accelerating out of turns when I ride. All these things are much harder to do on a heavier bike. It may or may not translate directly in pure speed depending on the type of terrain you are riding on.

    If you are riding up a perfectly smooth paved mountain road, it is the total weight of the Bike+rider that will dictate how much energy is spent getting up the hill. (Neglecting the friction that would be the same in both cases) Weather the weight is on the bike or the body doesn't make a difference.

    At the opposite end of the spectrum is if you are on a trail and your bike is light enough that you can bunny hop a log instead of rolling over it, you will save a lot of energy and go much faster. (In my experience, I can bunny hop much higher with a lighter bike)

    The real life is somewhere in the middle, the gains you get from a lighter bike might depend on the riding style but one thing is for certain: a lighter bike won't make you slower!

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    Quote Originally Posted by ghettocruiser View Post
    This means I am seeing only 13% slower times on a bike that weighs twice as much.
    I think you are forgetting that it requires more than 2x the energy input to go twice as fast on a bike. Air drag increases with the square of the speed. The same with inertia (or kinetic energy). Air drag is the reason why I can easily ride at 15mph while a Tour de France champion can barely ride at 30mph for a sustained period of time. (Even if he has way more than twice my power output).
    On a mountain bike, inertia plays more of a role but it is the same principle.

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    These trails are very tight wooded singletrack and my speeds are below 15 kph no matter what bike I'm riding. I'm gonna assert that the difference in air resistance between 12 kph and 14 kph is marginal.
    The above statements have not been evaluated by the Food and Drug Administration

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    Increasing speed from 12 to 14km/h leads to a ~36% increase in drag.....

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    You should do an experiment by yourself!

    Buy two 1 gallon water jugs and put them in your backpack and ride.
    On the way back attach the two water jugs to your bike rack and see!

    For the road and touring, the heavier bike is okay.
    For trail and technical rides you need a lighter bike.
    Best month for MTB is June!

  86. #86
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    Quote Originally Posted by hedgeboar View Post
    Increasing speed from 12 to 14km/h leads to a ~36% increase in drag.....
    Which at that speed is a difference of... 7 watts. Less, actually, because the handlebars on the FR bike are almost a foot higher than the XC hardtail, so it's fair to say that aerodynamics (such as they are at 14kph) favour the light bike.

    Now all of that said, there is some sleight of hand here on my part, since the FR bike does not have the ride characteristics of carbon hardtail with lead weights strapped to it. It rails down hills by comparison, which is particularly important, since by default, I'm a relatively crappy descender .
    The above statements have not been evaluated by the Food and Drug Administration

  87. #87
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    I know at 25mph 75% of your energy goes into fighting air resistance, it'll vary depending on what your wearing and your size, if your sat up or head down ofcourse.

    That is why there really isn't much in MTB to road bike speeds, MTB on road can average 16mph, where as roadie on the same terrain gets 18mph despite the tires being slicks and 1/2 the bikes weight.

  88. #88
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    Quote Originally Posted by featured View Post
    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.
    Now that is good data. Intuitively it makes sense to me but how can it be explained?

    I'm thinking we are already used to moving our body at whatever weight it is (because it changes slowly and we use it constantly). We have developed the strength and endurance needed to match our physical weight as well as the regular physical demands our body faces, all day - every day. A bicycle is a separate machine and separate weight/mass and only a small part of our "all day - every day" physical demands. That may be part of why we feel the difference in bike weight more than body weight.

    "I must not be crazy because I'm seriously questioning my sanity"

  89. #89
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    Quote Originally Posted by ghettocruiser View Post
    Looking at the split times between my carbon hardtail and my FR bike on the same undulating section of singletrack, I'm seeing a direction relationship between the weight of the total system and the speed.
    Using the same tires? So equal rolling resistance from the tires?
    Titux X Carbon 2010 race 9.93kg
    Titux X 2009 "Deore 2012" training 11.55kg

  90. #90
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    These types of discussions always make me laugh.

    It usually boils down to the fat guy saying power and acceleration and the skinny guy saying agility and climbing.

    All things being equal, of course being a light person is better for riding.

    joint wear, overcoming gravity etc.... However this is the real world and thing aren't equal. There is something called athletic ability or skillz or whatever you want to call it.

    I'll take talent over anything out there.

  91. #91
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    Yes, it doesn't mattter what you use. You can get through anything if you have enough skill with reasonably fast times.
    Titux X Carbon 2010 race 9.93kg
    Titux X 2009 "Deore 2012" training 11.55kg

  92. #92
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    In a pure physics perspective whether the mass is added to the bike or the rider is irrelevant. Basic equations for kinetic energy (K=0.5mv^2) and momentum (p=mv) require the total mass of the system. So if you were to the think of your motions on the bike (ie: braking and accelerating) then your stopping distance for braking and required net force to accelerate at the same rate would be the same whether you had a heavier bike and lighter body or heavier body and lighter bike.

    Where this argument is slightly skewed is that our body is not "rigid" to the bike. We apply forces to the bike that allow the bike to change direction separately from our bodies (ie: whip, bunny hop, wheelie). This is where Soya (2nd post) is right. When the weight of the bike is decreased by 50% then less force is required to change the bikes velocity (magnitude and direction). When we change our bodies mass we can't feel this change because moving ourselves is so intuitive.

  93. #93
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    Quote Originally Posted by bigfruits View Post

    shedding 20lbs of body fat will not feel like youre riding a 5lb bike.
    Yes it will, assuming that you have not lost any power in the process.
    It's the equivalent of riding with and without a 20lb plate in your back pack. Go attack a long climb w/ 20lb of ballast in your pack and see what it feels like. Will feel like HELL and you will be MUCH slower.

    This idea that the bike is being lifted has been overstated. When you bunny hop, you are lifting your body weight, as well as the bike. You are crouching to allow the bike to continue to rise as your body stops rising. It is the equivalent of doing a vertical leap w/ 25lbs of ballast in a pack, NOT just lifting 25lbs.

    When going over rough terrain, you are using your arms and legs as shock absorbers to suspend your body weight. When going through turns and jumps you are using your core to control your body weight. When landing from a jump/drop, you are using your arms/legs to support your bodyweight plus gravity, not bike weight. Same thing when entring a banked turn at speed - the rider is supporting his weight under G forces that want to push his body down into the bike. When unweighting the front wheel you are leaning your body weight backwards. Leaning a 25 lb bike from side to side is of almost zero consequence compared to these other "heavy lifting" activities a rider constantly does with his body.

    Bike weight is miniscule in the grand scheme. If you are an elite athlete and have no bodyfat that you can lose without losing power, then shedding bike weight is THE ONLY WAY, but for the average joe to freak out over a few lbs of bike weight is crazy when he can lose 10 lbs of body weight and have a much larger impact on performance.

    Caveat: I too still like to buy nice light weight stuff!
    '95 M2 StumpJumper FS
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  94. #94
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    Quote Originally Posted by APIOQM View Post
    In a pure physics perspective whether the mass is added to the bike or the rider is irrelevant. Basic equations for kinetic energy (K=0.5mv^2) and momentum (p=mv) require the total mass of the system. So if you were to the think of your motions on the bike (ie: braking and accelerating) then your stopping distance for braking and required net force to accelerate at the same rate would be the same whether you had a heavier bike and lighter body or heavier body and lighter bike.

    Where this argument is slightly skewed is that our body is not "rigid" to the bike. We apply forces to the bike that allow the bike to change direction separately from our bodies (ie: whip, bunny hop, wheelie). This is where Soya (2nd post) is right. When the weight of the bike is decreased by 50% then less force is required to change the bikes velocity (magnitude and direction). When we change our bodies mass we can't feel this change because moving ourselves is so intuitive.
    Great Post !

    Some of the posts I read here would give my Physics Professor a stroke...

  95. #95
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    Quote Originally Posted by Stumpjumpy View Post
    Yes it will, assuming that you have not lost any power in the process.
    It's the equivalent of riding with and without a 20lb plate in your back pack. Go attack a long climb w/ 20lb of ballast in your pack and see what it feels like. Will feel like HELL and you will be MUCH slower.

    This idea that the bike is being lifted has been overstated. When you bunny hop, you are lifting your body weight, as well as the bike. You are crouching to allow the bike to continue to rise as your body stops rising. It is the equivalent of doing a vertical leap w/ 25lbs of ballast in a pack, NOT just lifting 25lbs.

    When going over rough terrain, you are using your arms and legs as shock absorbers to suspend your body weight. When going through turns and jumps you are using your core to control your body weight. When landing from a jump/drop, you are using your arms/legs to support your bodyweight plus gravity, not bike weight. Same thing when entring a banked turn at speed - the rider is supporting his weight under G forces that want to push his body down into the bike. When unweighting the front wheel you are leaning your body weight backwards. Leaning a 25 lb bike from side to side is of almost zero consequence compared to these other "heavy lifting" activities a rider constantly does with his body.

    Bike weight is miniscule in the grand scheme. If you are an elite athlete and have no bodyfat that you can lose without losing power, then shedding bike weight is THE ONLY WAY, but for the average joe to freak out over a few lbs of bike weight is crazy when he can lose 10 lbs of body weight and have a much larger impact on performance.

    Caveat: I too still like to buy nice light weight stuff!
    When you bunny hop, you are actually SHIFTING your body weight in relation to the bike. So with combination of preloading shocks/tires, pulling and shifting weight - you can go airborne.

    Great points made in this thread. Reducing bike weight helps with handling, rotational weight helps with acceleration,. but body +bicycle weight account for total work performed.

    Work = mass x acceleration x distance.
    Acceleration includes overcoming gravity constant during every climb.

  96. #96
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    There are a lot of factors that influence the "feel" of a bike, and the feel of a bike-rider system, including center of mass, rotational mass versus non-rotating, and rider mass versus bike mass, but over the course of a ride, system mass drives the equation. Rider mass (and weight) impacts the system exactly the same as bike weight. You may not want to believe this, but on a bike, even at lower speeds, aerodynamics make a much bigger impact on average speed over a long ride than the addition or subtraction of a few hundred grams of weight.

  97. #97
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    After I lost some weight (both fat and muscle) I noticed that I climbed faster than before, alot faster. On the same bike.

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