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  1. #1
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    New question here. Aren't heavy wheels sometimes a good thing?

    Most of the time, fat-bike riders and builders are looking to lighten their wheels: with drilled-out, single-walled, rims and 120tpi tires. For climbing and quick handling, this makes sense. But, under some conditions, doesn't a little extra rolling inertia come in handy? Like riding through snow, perhaps?

    Curious, Dave.

  2. #2
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    I don't think you're crazy for thinking that.
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    I do, you have to create inertia before you can use it.

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    For me personally in the summer considering my physical abilities and size (fat and not super fit), where I ride (Minnesota) and the speed I ride (medium fast) I find a fat bike with 3.7 inch tires is the fastest and most efficient use of my energy over an entire ride. I also think what is true is different for everyone. Little skinny racer on tight climbing course would likely be fastest on a 26 inch wheel. My personal order of speed on my bikes from fastest to slowest is 3.7 inch tire fat bike, 29r, Moonlander with100mm rim and the big tires and then 26 inch mtb bike. I think a big part of why 29r wheels are faster for some people has a lot more to do with the weight of the wheel helping it roll better rather than the size alone allowing it to roll better. Even if a 29 and 26 inch wheels weigh the same pushing that weight way out there on a 29r makes it ride like a heavier wheel which I find benefits me.
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  5. #5
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    Quote Originally Posted by Hogdog View Post
    I do, you have to create inertia before you can use it.
    For some of us, overcoming the inertia of our own bodies is much more of a challenge than that of a heavier wheel.

    I always laugh when I see guys creaming themselves over the latest lightweight do-dad that they're planning to drop big bucks on to shave a gram or two when they're rolling with bellies that are barely contained by their jersey.

    I'm a clyde and ride my old school Large Marge wheels. Yeah, it'd be nice to shave some weight there, but would probably be better served by losing a few pounds off myself before losing anything off the bike. I can spin the LMs up quick enough and can climb well enough with them because I have the size and strength to do so. Would lighter wheels help me ride better/faster? Probably, but I go back to the rider issue - until I get down under 240 I don't see the point in losing weight on the bike.

  6. #6
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    Quote Originally Posted by BluNosDav View Post
    Most of the time, fat-bike riders and builders are looking to lighten their wheels: with drilled-out, single-walled, rims and 120tpi tires. For climbing and quick handling, this makes sense. But, under some conditions, doesn't a little extra rolling inertia come in handy? Like riding through snow, perhaps?

    Curious, Dave.
    Given that light for a fatbike wheel is still heavy in the MTB world I don't see any benefit to having a heavier fatbike wheel given the current constraints in technology.

    I've never been riding through sand or snow and wished for more weight in the wheels.

    The issue with lightweight and fatbike wheels is that the tires/tubes are reaching the point where there are durability penalties for going lighter and lighter.

    What's more important to me is having tires that have the lowest rolling resistance and that still meet my other needs. Slow rolling tires suck energy from you with every pedal stroke and that's no fun on a long ride.

    Of course you have to balance low RR with getting the traction you need and adequate durability.
    Safe riding,

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  7. #7
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    I'd rather ride a sub 30 lb fat bike compared to a 40+ beast of course, but I agree, no need to go too crazy with it.
    Biggest difference I've found is the tires themselves. Sure is easier to roll a hudu than a nate yah know?

    But overall wheel weight, it's just a different type of riding. Once the heavy fatties are up to speed, they pull you through corners & speed up down hill.
    Switching to skinny tires for a bike trip couple years ago, I was way more tired when i wasn't used to how quickly the skinny tires would lose momentum. (on the same trails)

  8. #8
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    I don't think any extra weight on a bike, rotating or otherwise will ever make anyone faster overall over the course of a ride, race, or whatever. There may be some short climbs, or rough sections that the additional momentum will keep you from losing speed as quickly, but this will be more than made up for when having to brake earlier, and accelerate more slowly when necessary.

    Now, if the extra weight is giving you something else in return, like traction, or shock absorption, it may help you go faster, so heavier can be better, but not on it's own.

    Maybe you could take the flywheel effect to an extreme, and use it to store energy from braking with a gear system to spin up a separate flywheel mounted next to the wheel, then use that to accelerate.

  9. #9
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    Quote Originally Posted by autodoctor911 View Post
    I don't think any extra weight on a bike, rotating or otherwise will ever make anyone faster overall over the course of a ride, race, or whatever. There may be some short climbs, or rough sections that the additional momentum will keep you from losing speed as quickly, but this will be more than made up for when having to brake earlier, and accelerate more slowly when necessary.

    Now, if the extra weight is giving you something else in return, like traction, or shock absorption, it may help you go faster, so heavier can be better, but not on it's own.

    Maybe you could take the flywheel effect to an extreme, and use it to store energy from braking with a gear system to spin up a separate flywheel mounted next to the wheel, then use that to accelerate.
    I agree with the above.

    I will also add that people overstimate the amount of inertia you actually gain with heavy wheels.
    If you hit a rock, the total energy of you plus the bike is what will get you over the rock, and the wheels are a small fraction of that energy.

    For example, a 90 kg guy on a 10 kg bike going 15 meters/second (about 10 mph).

    Total energy = 1/2MV^2
    = 11250 KgM^2/sec^2 = 11250 joules

    so what about rotational energy of the wheel? Well, the total energy of the wheel is the sum of translational and rotational energy, and works out to be,
    E=MV^2 (ask me to derive this and I will!)
    so the total energy of the rotating wheel is twice that of a non-rotating wheel translating at the same speed.

    For a 2 kg wheel
    E = 450 joules
    compared to the total energy of 11250 joules, it is 4% of your total energy. The rotational energy is half of that, but there are 2 wheels.

    So the rock you hit doesn't see much difference whether you have heavy wheels or not. But if you want more inertia, you can fill up your backpack with lead wieghts. Clearly, inertia is not the goal you should be striving for.

  10. #10
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    in you were in a competition where you were riding off the top of a 100foot cliff, and the winner was the person to land farthest from the bottom of the cliff, then heavy tires would help. outside of that, i don't see any benefit. trying to spool up the especially heavy wheels of my beast isn't gratifying in any way. now, gyroscopic forces so large you can feel them, that is kind of fun...

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    Thanx for all the opinions guys. Makes this all more interesting.

    Two other heavy rolling (non-bike) examples to ponder:

    #1 - I once had a pick-up truck that got 17mpg running around town, and 20mpg on the highway during long trips. I always kept close track of my milage. Then one day, I was hauling some really heavy steel equipment on a long trip. My truck was propably overloaded weight-wise, but, everything fit inside the bed, so there was no extra wind-drag. I got over 23mpg on that trip! It was gently rolling terrain (not mountainous) and the momentum of all that steel, just kept carrying my truck along, with my speed hardly varying at all. More weight was more better, and my truck's engine didn't have to work as hard throughout the trip, except for the initial acceleration getting it up to highway speed.

    #2 - I used to own a farm tractor (John Deere), and a small farm. Sometimes, when working through some muddy areas, it would lose traction and the wheels would spin-out. My fellow farmers told me to fill the tires about 90% full of water (and some anti-freeze for winter). They did this through the valve stems, when the stems were up high at the 12 o'clock position, so about 10% of the tire at the top, still had air. Now, we're talking several hundreds of pounds of added water weight, maybe even thousands of pounds on their large dually tractors. I asked them about all the extra engine power (and diesel fuel) it was gonna take to roll all this water back & forth across the fields. They just laughed and said that the water doesn't rotate at all. The wheel just revolves around, and the water keeps slipping along inside the circle, as if it's in an endless tunnel. Sure enough, I never noticed any additional fuel usage, never had to run the diesel at any higher RPM, and my tractor quit slipping in the muddy areas. Go figure?

    Don't know how these 2 examples translate over to fat-bikes? But, it all involved changing weight, on wheels, without using more energy.

    Thanx, Dave.

  12. #12
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    I've always felt like heavier wheels could provide me an advantage during races... so long as they were on the other guy's bike!

    Seriously though, I could imagine instances when the increased gyroscopic stability of heavier wheels would allow you to hold a line better and avoid braking or scrubbing more speed in turns. I just think that benefit is so rare an occurrence (on x-country rides) compared to all the times you would be hindered by slowly bringing heavier wheels up to any speed that my first sentence holds true.

    It also seems like any benefit from heavier wheels would more commonly exist in downhill situations where maintaining the ideal line might allow you to maintain speed and the effort to bring wheels up to high speed is easier with the gravity assist. Indeed downhill racers don't seem overly concerned about wheel weight (or total bike weight).

  13. #13
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    Quote Originally Posted by Bill in Houston View Post
    in you were in a competition where you were riding off the top of a 100foot cliff, and the winner was the person to land farthest from the bottom of the cliff, then heavy tires would help. outside of that, i don't see any benefit. trying to spool up the especially heavy wheels of my beast isn't gratifying in any way. now, gyroscopic forces so large you can feel them, that is kind of fun...
    Show me the math.

    The bike that's going to land the farthest from the bottom of the cliff will be the one that's going the fastest when it becomes airborne. Assuming that the aerodynamics between the bikes is the same.
    Riding Fat and still just as fast as I never was.

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    The "feeling" most people cling to (and parrot) is that "heavier rotating mass kills acceleration". This is generally not true at all for big heavy cars, although it can be true. Most things we fret about make no appreciable difference in the grand scheme of things.

    Rotating Mass, Available Horsepower, and Acceleration
    Quote Originally Posted by BluNosDav View Post
    Most of the time, fat-bike riders and builders are looking to lighten their wheels: with drilled-out, single-walled, rims and 120tpi tires. For climbing and quick handling, this makes sense. But, under some conditions, doesn't a little extra rolling inertia come in handy? Like riding through snow, perhaps?

    Curious, Dave.
    I gotta agree with you Dave ... There will always be a condition where rolling inertia can be used to advantage.

    And there will always be an argument for and against the condition

  15. #15
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    Quote Originally Posted by BluNosDav View Post
    Thanx for all the opinions guys. Makes this all more interesting.

    Two other heavy rolling (non-bike) examples to ponder:

    #1 - I once had a pick-up truck that got 17mpg running around town, and 20mpg on the highway during long trips. I always kept close track of my milage. Then one day, I was hauling some really heavy steel equipment on a long trip. My truck was propably overloaded weight-wise, but, everything fit inside the bed, so there was no extra wind-drag. I got over 23mpg on that trip! It was gently rolling terrain (not mountainous) and the momentum of all that steel, just kept carrying my truck along, with my speed hardly varying at all. More weight was more better, and my truck's engine didn't have to work as hard throughout the trip, except for the initial acceleration getting it up to highway speed.

    #2 - I used to own a farm tractor (John Deere), and a small farm. Sometimes, when working through some muddy areas, it would lose traction and the wheels would spin-out. My fellow farmers told me to fill the tires about 90% full of water (and some anti-freeze for winter). They did this through the valve stems, when the stems were up high at the 12 o'clock position, so about 10% of the tire at the top, still had air. Now, we're talking several hundreds of pounds of added water weight, maybe even thousands of pounds on their large dually tractors. I asked them about all the extra engine power (and diesel fuel) it was gonna take to roll all this water back & forth across the fields. They just laughed and said that the water doesn't rotate at all. The wheel just revolves around, and the water keeps slipping along inside the circle, as if it's in an endless tunnel. Sure enough, I never noticed any additional fuel usage, never had to run the diesel at any higher RPM, and my tractor quit slipping in the muddy areas. Go figure?

    Don't know how these 2 examples translate over to fat-bikes? But, it all involved changing weight, on wheels, without using more energy.

    Thanx, Dave.
    In example 1, I have to say that there is no way a loaded truck gets better mileage than an empty one, despite your observation. Moving mass takes energy. Imagine running up and down some hills while pushing an empty shopping cart. Now load the cart with bricks. Is your running going to be harder or easier?

    Example 2 - it would take more energy if you had to spin the water, and its true you don't, but you are still moving the water when you move the tractor which also takes energy. Loss of traction on the other hand is a loss of energy also, so there is a trade off.

  16. #16
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    Theoretically, an empty truck and a full truck rolling down a hill will go the same speed and get to the bottom at the same time. If they then continue to roll up a hill on the other side, they will reach the same height. But after they slow down it will take more energy to keep the loaded truck moving.

  17. #17
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    The truck full of steel got better mileage because it's ride height was lower, which improved the aerodynamics. Also the steel filled some portion of the bed, which also improves the aerodynamics. There's also quite a body of literature on "pulse-and-glide", which is what you were doing going up and down the hills.

    Quote Originally Posted by crashtestdummy View Post
    Show me the math.
    No. I assumed that the extra weight was in the form of a hang-glider attached to the top of the bike. a-HA! If you can shoot someone down by changing the assumptions, then so can I!

  18. #18
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    The math is simple:

    Energy = work = force x distance. More mass =, more force = more energy needed.

  19. #19
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    This is an interesting thread because I was wondering the same thing the other day.

    Basically the Physics I know is contrary to my perception when I switched from my fatbike to an ordinary 26" bike. The heavy fatbike felt smoother and easier to pedal up a moderate grade, yet it should not be so in theory. There's obviously other factors involved.
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  20. #20
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    Well - the story I seem to recall is from mikesee, the application being riding in deep snow (yo: he would know). If I recall right, he found himself in a situation where riding through successive snow drifts got progressively easier (easier being an extremely relative term here), and noticed that his rims had acquired snow buildup.

    Like a flywheel.

    I don't know. It sort of makes sense. Are lighter bits better 80% or whatever% of the time? Yeah probably. But there are other times where maybe it isn't so critical.

    Feel free anyone (Mike particularly) to correct the gaps in my memory.
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  21. #21
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    If you are going to roll down a hill and bash through a snow drift, then yeah, you want your bike to be heavy. But if you have to pedal it up to speed and bash through it, you use more energy to get the heavy bike up to speed. Then, when the heavier and lighter bikes are both up to the same speed, the heavier bike goes through the snow drift more easily, but the energy you feel you have saved through the drift was used before you hit the drift. Overall, on a heavier bike, you will use more energy.

  22. #22
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    Quote Originally Posted by smilinsteve View Post
    Theoretically, an empty truck and a full truck rolling down a hill will go the same speed and get to the bottom at the same time. If they then continue to roll up a hill on the other side, they will reach the same height.
    Nope.. Theoretically full truck rolls faster. More gravitational pull against the same windage. Higher speed at the bottom and the full truck ends up higher up the next hill. After that point the lighter one rules. So in the end it depends if you live on top of the hill or not..

  23. #23
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    Quote Originally Posted by TeddyTS View Post
    Nope.. Theoretically full truck rolls faster. More gravitational pull against the same windage. Higher speed at the bottom and the full truck ends up higher up the next hill. After that point the lighter one rules. So in the end it depends if you live on top of the hill or not..
    Nope.. grab a pencil and a large bolt (different weight, about the same aerodynamics) drop them from the same height see which one hits the floor first?
    Report back with your findings. You can't get "more gravitational pull", it is constant.

  24. #24
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    Quote Originally Posted by temporoad View Post
    Nope.. grab a pencil and a large bolt (different weight, about the same aerodynamics) drop them from the same height see which one hits the floor first?
    Report back with your findings. You can't get "more gravitational pull", it is constant.

  25. #25
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    Quote Originally Posted by TeddyTS View Post
    Nope.. Theoretically full truck rolls faster. More gravitational pull against the same windage. Higher speed at the bottom and the full truck ends up higher up the next hill. After that point the lighter one rules. So in the end it depends if you live on top of the hill or not..
    Yeah, this is true, but isn't what anyone else was talking about. My car with 1000 lbs of feathers in it will roll down a hill a lot faster than a cardboard box on wheels the same size and shape as my car, and will roll farther up the next hill. You used incorrect verbiage that people will argue with, but you are right.

  26. #26
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    Quote Originally Posted by smilinsteve View Post
    The math is simple:

    Energy = work = force x distance. More mass =, more force = more energy needed.
    Where's the rest of it?

    Show me where in that equation you've factored in steep tilted sandstone slabs, polished granite boulders, slimy debarkified logs, deep dry beach sand, well-hydrated-baby-poop mud, cross-grained and pre-greased roots, ballroom ice under ~2% moisture content snow, kitty litter over hardpack, and ridgeline crosswindfests.

    No hurry--I'll wait.

  27. #27
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    Quote Originally Posted by mikesee View Post
    Where's the rest of it?

    Show me where in that equation you've factored in steep tilted sandstone slabs, polished granite boulders, slimy debarkified logs, deep dry beach sand, well-hydrated-baby-poop mud, cross-grained and pre-greased roots, ballroom ice under ~2% moisture content snow, kitty litter over hardpack, and ridgeline crosswindfests.

    No hurry--I'll wait.
    Actually, its all in there, can't you see it?

  28. #28
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    Quote Originally Posted by Bill in Houston View Post
    Yeah, this is true, but isn't what anyone else was talking about. My car with 1000 lbs of feathers in it will roll down a hill a lot faster than a cardboard box on wheels the same size and shape as my car, and will roll farther up the next hill. You used incorrect verbiage that people will argue with, but you are right.

    hmm...

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    How about we just start with how exactly work = energy?
    Whatever floats your bike, dude

  30. #30
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    Quote Originally Posted by Dustin Mustangs View Post
    How about we just start with how exactly work = energy?
    That's just plain old physics definitions.

    Work = Force x distance

    = mass x acceleration x distance

    With units of kg x meters/ second squared x meters

    1 kg meter squared per second squared = 1 joule, a unit of energy.

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    Holy crap man, you rewrote the physics books with that one! So if a F35 joint strike figher weighing around 30,000 lbs crashes into the side of a mountain at mach 1.5, by your 'plain old physics definitions', it does so with zero energy? Oooooo kaaaaaaay then.
    Whatever floats your bike, dude

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    Quote Originally Posted by Dustin Mustangs View Post
    Holy crap man, you rewrote the physics books with that one! So if a F35 joint strike figher weighing around 30,000 lbs crashes into the side of a mountain at mach 1.5, by your 'plain old physics definitions', it does so with zero energy? Oooooo kaaaaaaay then.
    I didn't rewrite the physics book. You just haven't gotten to that part yet , I guess.

    Work is energy.
    if you disagree with that I suggest you rent a google machine and look it up.

    That plane's energy is kinetic energy = 1/2 MV^2. The units are the same as work: kg M^2/sec^2.

    Keep reading that physics book.

  33. #33
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    Quote Originally Posted by smilinsteve View Post
    Actually, its all in there, can't you see it?
    Nope, I'm mathtarded. Guess I'll have to wait for you to spell it out for me.

    I suspect I might be waiting awhile, because the fact is there are *lots* of times when added mass is more efficient. Like many of the not-quite-so-tongue-in-cheek examples I gave above.

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    Quote Originally Posted by mikesee View Post
    Nope, I'm mathtarded. Guess I'll have to wait for you to spell it out for me.

    I suspect I might be waiting awhile, because the fact is there are *lots* of times when added mass is more efficient. Like many of the not-quite-so-tongue-in-cheek examples I gave above.
    Your not so tongue in cheek examples make me picture myself on a heavy bike and hating it.

    Mass is swell when gravity is what's moving your bike. I agree that there are lots of times when mass is good; times when you are going downhill.
    If your body needs to generate the energy to move your bike, then you don't want more mass.

  35. #35
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    Quote Originally Posted by smilinsteve View Post
    Your not so tongue in cheek examples make me picture myself on a heavy bike and hating it.

    Mass is swell when gravity is what's moving your bike. I agree that there are lots of times when mass is good; times when you are going downhill.
    If your body needs to generate the energy to move your bike, then you don't want more mass.
    You're arguing your emotional stance, which is fine--you feel how you feel. But--really? My examples were, um, *mountain biking*.

    Perhaps you're one-a-them "roadies" I've heard about?!

    (shivers)

    OK, so you've got an emotional response but you've offered no actual proof that added mass is always bad. I have lots of proof that it's good, and I'm not talking *at all* about descending.

    Come ride with me some time--I'll take you on some real fun trails where you can push your light bike to the top while I (and others) on big fat pigs are still riding.

    Once at the top we'll wait for you to arrive, wait more for you to catch your breath, and still more for you to confabulate an equation that explains what just happened...

    Probably won't wait much on the descent though...


  36. #36
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    Quote Originally Posted by mikesee View Post
    You're arguing your emotional stance, which is fine--you feel how you feel. But--really? My examples were, um, *mountain biking*.

    Perhaps you're one-a-them "roadies" I've heard about?!

    (shivers)

    OK, so you've got an emotional response but you've offered no actual proof that added mass is always bad. I have lots of proof that it's good, and I'm not talking *at all* about descending.

    Come ride with me some time--I'll take you on some real fun trails where you can push your light bike to the top while I (and others) on big fat pigs are still riding.

    Once at the top we'll wait for you to arrive, wait more for you to catch your breath, and still more for you to confabulate an equation that explains what just happened...

    Probably won't wait much on the descent though...

    Emotion has nothing to do with it (on my end):

    Psychological projection - Wikipedia, the free encyclopedia

    If you don't understand physics, don't argue about physics.

    If you can pedal your heavy bike up a hill, while I am pushing my light bike, the only reason would be that your body can generate the necessary energy to do so, while my body could not, even though the required energy for me would be less. The heavy bike would offer no advantage.

    It takes more energy to move more mass. Its that simple. Don't be mad at me, or at physics.
    That's just the way god made the world.

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    Quote Originally Posted by smilinsteve View Post
    I didn't rewrite the physics book. You just haven't gotten to that part yet , I guess.

    Work is energy.
    if you disagree with that I suggest you rent a google machine and look it up.

    That plane's energy is kinetic energy = 1/2 MV^2. The units are the same as work: kg M^2/sec^2.

    Keep reading that physics book.
    Oh no no no, lets not throw real equations into the mix, we are using the one you posted above. E = W = F x D. In the plane scenario, what exactly would D equal? Unless you think that plane can move a mountain it would be zero, and therefore so would E. I am not saying work and energy are not related, or that they cannot be equal, but to just assume they always are is wrong. That might be tough to look up in this book you keep talking about.

    Back to the original topic... how about a heavy wheel's flywheel characteristic and how its ability to store energy plays a role in required power output. If you know how to ride a fatbike, and that's a big if, than you use this to start building the energy needed to climb a hill before you even get to it. Sure you can do this with a light wheelset too, but not as efficiently due to drag (which is a big deal at the power level and speed of a bike). This can allow you to climb the same hill on a FB with less power than on a MTB or, as I think Mike was getting at, maybe climb a hill on a FB that you couldn't on a MTB.
    Whatever floats your bike, dude

  38. #38
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    there is a reason that Prius cars, and hill climbing race cars, and tour de france race bike for hill stages, have light wheels rather than big heavy ones.

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    Quote Originally Posted by Dustin Mustangs View Post
    Oh no no no, lets not throw real equations into the mix, we are using the one you posted above. E = W = F x D. In the plane scenario, what exactly would D equal? Unless you think that plane can move a mountain it would be zero, and therefore so would E. I am not saying work and energy are not related, or that they cannot be equal, but to just assume they always are is wrong. That might be tough to look up in this book you keep talking about.
    Work is energy and = F x D. Are you doubting this?
    Are you saying the formula for kinetic energy is real, and the formula for work is not?

    What if I take a rock and carry it up a hill? Haven't I added a potential energy to it, equal to mgh? Do you believe in that? (The rock isn't moving at the top of the hill btw).

    Do you believe that heat is energy? Do you believe that heat can be converted to work? that work requires energy, that potential energy can be converted to kinetic energy, that the calories can convert to work your muscles do, or to kinetic energy of your body in motion?

    If you burn a piece of wood, you are releasing energy. You can feel the heat, but you are doing no work, there is no mass, no velocity, etc. In other words, it seems like your understanding of energy is incomplete.


    Back to the original topic... how about a heavy wheel's flywheel characteristic and how its ability to store energy plays a role in required power output. If you know how to ride a fatbike, and that's a big if, than you use this to start building the energy needed to climb a hill before you even get to it. Sure you can do this with a light wheelset too, but not as efficiently due to drag (which is a big deal at the power level and speed of a bike). This can allow you to climb the same hill on a FB with less power than on a MTB or, as I think Mike was getting at, maybe climb a hill on a FB that you couldn't on a MTB.
    Flywheels store energy, but they don't create energy. I understand the feeling of being on a heavy bike, in that it has more inertia and therefore resists changes in velocity more than a lighter bike. But, that extra energy you feel on your heavy bike is energy that your legs had to generate and put into that bike. (Chemical energy from food calories converted to force of muscular contraction acting over a distance of your pedal stroke resulting in kinetic energy of your body and bike in motion etc).

  40. #40
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    Quote Originally Posted by smilinsteve View Post
    Emotion has nothing to do with it (on my end):

    Psychological projection - Wikipedia, the free encyclopedia

    If you don't understand physics, don't argue about physics.

    If you can pedal your heavy bike up a hill, while I am pushing my light bike, the only reason would be that your body can generate the necessary energy to do so, while my body could not, even though the required energy for me would be less. The heavy bike would offer no advantage.

    It takes more energy to move more mass. Its that simple. Don't be mad at me, or at physics.
    That's just the way god made the world.
    Not mad. Pretty happy actually, though that could just be gas...

    Not arguing the fact that more energy is required. Don't think anyone is. The OP postulated that there are times when more mass is better. You're arguing from a purely theoretical view that he's wrong, while I have heaps of anecdotal evidence that says he is (at times) right.

    Who's right?

    Depends on perspective. Nobody really.

    If you want to *walk* your light bike up a tough climb that's *rideable* on a heavier, more planted, less likely to spin-out pig, that's your prerogative. I find riding a lot more enjoyable than walking, energy use be damned, and there are many, many, many times on any given ride where added wheel mass keeps me riding and brainwashed tunnel-vision guys like you, regardless of fitness or skill level, walking.

    To each his own.

    Cheers,

    MC

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    I think those of us coming from a heavy wheel can be helpful stand point often clash with the folks with the physics formulas because they see us as denying basic physics. I want to make it clear that I believe the math that says the total amount of energy to move a heavier bike/wheel is more and will always be more. But and this is the but I think all those with a physics 101 backgrounds are missing is that the power output on a fatbike is a human and not an electric motor. Humans don't apply a constant amount of energy to the pedals but rather in spurts of each pedal stroke and in spurts like when doing interval work. I find that on my fatbike although I ultimately use more energy over an entire ride I can apply that energy in a way more conducive to a humans power output making me faster.
    laotzucycles.blogspot.com

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    Clearly this is the case of another conspiracy that is tied to Obama.

    Hmmmn??

    If Rush Limbaugh was wedged in the spokes of your rear wheel and Obama was wedged in the front wheel would your bike be less stable as the rear wheel seemed to want to overtake the front wheel on the downhills?

    Would there be a steering issue as the rear wheel leaned to the right but the front leaned to left?

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    Quote Originally Posted by temporoad View Post
    Nope.. grab a pencil and a large bolt (different weight, about the same aerodynamics) drop them from the same height see which one hits the floor first?
    Report back with your findings. You can't get "more gravitational pull", it is constant.
    I'd recommend you to do the the test, let's say from 10 stories hight.

  44. #44
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    Momentum!
    Lucky neighbor of Maryland's Patapsco Valley State Park, 39.23,-76.76

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    Quote Originally Posted by TeddyTS View Post
    Nope.. Theoretically full truck rolls faster. More gravitational pull against the same windage. Higher speed at the bottom and the full truck ends up higher up the next hill. After that point the lighter one rules. So in the end it depends if you live on top of the hill or not..
    I originally thought you were wrong, but now you get a green chicklet for pointing this out!
    The normal "rolling down a ramp" experiments ignore air resistance. Bill from Houston's extreme example of a cardboard truck made me realize that air resistance in some cases can not be ignored. (thinking of extreme cases is an excellent way of testing a hypothesis).
    In the case of big trucks the difference between empty and loaded wieghts is significant, and the air resistance can be very significant especially at higher velocities. So, for a long hill where speeds built up to some significant level, the wind resistance could in fact hold the lighter truck back more than the heavier one.

    For mountain bikes however, I think ignoring air resistance in the same experiment is a good assumption. The difference in weight between a light bike plus rider is not greatly different than the heavy bike plus rider - roughly 200 lbs vs 210 lbs or 5%? (In the truck example difference in weight between loaded and unlaoded is over 100%). And profile of bike riders is less and speeds are slower.

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    Quote Originally Posted by Bill in Houston View Post
    there is a reason that Prius cars, and hill climbing race cars, and tour de france race bike for hill stages, have light wheels rather than big heavy ones.
    Your examples all include pavement.

    I don't ride much of that. Especially not on a fatbike. Nor do I ride in a vacuum. I ride in the real world when there are lions and tigers and bears, and where added wheel mass allows me to crawl and gnash my way up, over, and through things where race-light wheels slip, spin, or bounce offline.

    Keep in mind I'm not arguing that you need the heaviest wheels possible. Just heavi*er* than the ricky racer light stuff that most uneducated (<-somewhat tongue in cheek) riders covet.

  47. #47
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    These meandering threads are so much fun I may be able to cancel my cable TV subscription soon. After an hour of googling I've found that "bicycle dynamics" is a good search term to enter in order to learn more.
    I've also learned that the less I think the better I ride. YeeHaa!

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    How much of the better traction is from the added surface area of the tire and how much is from the extra weight not being knocked off line by things? I've always felt that the extra surface area of the tire was most of it at crawl up hill speeds. At downhill speeds or through sastrugi then, it seems to me, the weight component comes into play on the plus side. I guess the bottom line should be who cares just as long as we've got them to ride. Now if this thread can spin into a global warming discussion.....
    Latitude 61

  49. #49
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    Quote Originally Posted by mikesee View Post
    Not mad. Pretty happy actually, though that could just be gas...

    Not arguing the fact that more energy is required. Don't think anyone is. The OP postulated that there are times when more mass is better. You're arguing from a purely theoretical view that he's wrong, while I have heaps of anecdotal evidence that says he is (at times) right.

    Who's right?

    Depends on perspective. Nobody really.

    If you want to *walk* your light bike up a tough climb that's *rideable* on a heavier, more planted, less likely to spin-out pig, that's your prerogative. I find riding a lot more enjoyable than walking, energy use be damned, and there are many, many, many times on any given ride where added wheel mass keeps me riding and brainwashed tunnel-vision guys like you, regardless of fitness or skill level, walking.

    To each his own.

    Cheers,

    MC
    Glad to hear you are happy, but the really happy guys I know don't feel the need to insert an insult with every comment in a discussion.

    But that's ok man, I can see you are frustrated. So now we are down to agreeing that more energy is required to pedal a heavier bike with heavier wheels, but maybe that can sometimes be a good thing?

    I have previously pointed out that weight going downhill is a good thing, and extra inertia allows you to maintain speed more easily. Uphill however, I don't see an advantage. Going slow, you have almost no inertia, and you need to keep pedaling to keep moving, and each pedal stroke requires more energy. The same energy transferred to the pedals of a light bike and a heavy bike results in the light bike moving faster (if it maintains traction!!)

    But then you bring up being more "planted" and not spinning out, and I totally agree that traction is a very important part of climbing and fat bike tires could definitely provide that traction and stability, but I am pretty sure that that has to do mostly with the amount of rubber on the ground and the shape of the contact patch and the conformability of a big tire, and has little or nothing to do with the weight. In fact, if you could take those big fat wheels you love so much and make them lighter but the same in every other way, you would climb better.

    Signed,
    Brain washed, tunnel vision, uneducated, roadie, emotional, bike pushing, yet still smilin, steve.

  50. #50
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    Quote Originally Posted by mikesee View Post
    Your examples all include pavement.

    I don't ride much of that. Especially not on a fatbike. Nor do I ride in a vacuum. I ride in the real world when there are lions and tigers and bears, and where added wheel mass allows me to crawl and gnash my way up, over, and through things where race-light wheels slip, spin, or bounce offline.

    Keep in mind I'm not arguing that you need the heaviest wheels possible. Just heavi*er* than the ricky racer light stuff that most uneducated (<-somewhat tongue in cheek) riders covet.


    Again traction is the benefit you are describing, not the benefit of weight.

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