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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.

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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.

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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?

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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.

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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

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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
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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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    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.

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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?

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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.

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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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    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
    DH.FR.0ne
    Reputation: DH.FR.0ne's Avatar
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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
    ~Reformed Mechanic~
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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
    mtbr member
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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
    The Cheater
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    Entertainment? But we're so dead serious about performance gained from grams!
    Titux X Carbon 2010 race 9.93kg
    Titux X 2009 "Deore 2012" training 11.55kg

  50. #50
    It's the axle
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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.

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