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Thread: 6-foot drops?

  1. #1
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    6-foot drops?

    Does anyone know of or have experience with 6-foot drops on a full suspension stumpy? I have a stock 2011 Stumpjumper Elite (full suspension with mini brain) and have been eyeing a 6-foot drop on my favourite trail, but don't want to find out the hard way whether or not the bike can handle it (so yes, this has to already assume that I can, haha). I've heard that 4-foot drops are okay, but don't know about 6-foot drops on it.

    As well, if this is a go (meaning wheels, forks, and frame can handle it), what's the set up most have used in terms of psi and or suspension settings?

    Appreciate any suggestions.

  2. #2
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    how heavy are you? 6ft to flat ground or downhill landing?

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    my bad, forgot to include:
    i'm 205 lbs and landing area is relatively flat with a very slight decline

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    I would avoid it. Flat landings are always hard on a bike, especially when the rider is 205 pounds. If you are super smooth with a trials or bmx background, you could probably get away with it here and there. If not, you're just asking for trouble. It might not break right away, but you've stressed it and shortened its life. If you plan on replacing the bike at the end of the year, you might be ok.

  5. #5
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    It's not like the bike's going to burst into flames the first time you try it, but that's asking an awful lot out of what's really an XC bike. If you want to ride that kind of stuff at all regularly, you'd be a lot better off on something burlier.

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    thanks for the warnings, will pay heed.

    what about 4-foot drops to flat ground? could the stumpy take it or is that just an exaggeration? i bought it with the intention of abusing it, but not breaking it so still trying to figure out its real-life limitations rather than theoretical. i'm getting more interested in jumps now than i thought i would, but not looking to do any hero like stuff, just have some fun without breaking the bank again.

  7. #7
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    agree with the other posts. you and your bike, with skills, would probably be fine the first few times you send that. The problem is when you land it clean AND you have a giant grin on your face you'll hit that line EVERY time after & if you don't have the right set-up you might be asking a little too much of your bike and it'll get mad at you and stack you on the floor especially if it's pretty much to flat.

    not familiar with that frame. Is that the 150mm rear travel Stumpy? I'd probably dial up your suspension settings before you drop that. Sounds like you're about to have a s..tload more fun though!
    Last edited by 53119; 08-17-2011 at 08:17 AM.

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    Quote Originally Posted by weekendthrasher View Post
    thanks for the warnings, will pay heed.

    what about 4-foot drops to flat ground? could the stumpy take it or is that just an exaggeration? i bought it with the intention of abusing it, but not breaking it so still trying to figure out its real-life limitations rather than theoretical. i'm getting more interested in jumps now than i thought i would, but not looking to do any hero like stuff, just have some fun without breaking the bank again.
    I've got a 07 Stumpy and regularly hip 3-4ft drops and some doubles.No problems with it. Picked up an Enduro and wow what a big difference. Soaks it all up.
    Sent on my Droid while hitting that $h!t

  9. #9
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    I think your bike's name sake pretty much covers your question...
    It's a Stump jumper, not a tree, deck, small VWs, or hawt girls jumper And, I don't know of any 6 ft tall stumps...well, except this one guy...
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  10. #10
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    my bet is you could do it a few times but if you make a habit of it something is gonna give.

  11. #11
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    I'd do it on the bike, trying it out every now and then won't kill it. However if you make that into your everyday line and do that 3-5 times a week...your stumpy life may be reduce...kinda like having a double fudge chocolate cake every night for dessert.

  12. #12
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    Quote Originally Posted by 2clue View Post
    ...life may be reduce...kinda like having a double fudge chocolate cake every night for dessert.
    WHAT?! the hell are you saying?
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  13. #13
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    Quote Originally Posted by Pau11y View Post
    WHAT?! the hell are you saying?
    my thought too, that is not gonna kill me, is it?

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    Quote Originally Posted by b-kul View Post
    my thought too, that is not gonna kill me, is it?
    Screw that dude! If I'm going out cause I popped my tube, I'm going out w/ a full belly and a smile on my face!

    Naysayers never apologize. Critics go to their grave thinking everyone else is wrong.
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    Nom nom nom! Didn't say it would be a bad way for it/you to go! It's called living a full and completely life...a bit more on the full side!

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    your wheels are doubtful, suspension will want to bottom out fairly easily (need to pump them up!). I think one of the posters hit it on the nail, with proper technic you can land half way soft from 6ft, but most of us can't do that especially every time.

    4ft to flat is still fairly hard on a 5in bike...speed is your friend here!

    Part of me says go for it once and make sure you take a vid and post it up on this thread for us!
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  17. #17
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    Yeah your going to want bigger tires, DH type rims and well built to take that kinda abuse more than a few times, your frame will likely be fine as long as you don't mess up the landing them who knows could rip the head tube off or snap the forks fairly easily.

    Look for a cheap 2nd DH bike if I was you.

  18. #18
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    Just do it!Have a friend take pics or a video and report back!!!

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    As long as you can prove that the frame cracks BEFORE the crash, should be able to warranty the frame if it does fail.

  20. #20
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    I've done 6ft drops to down a few times on an 03 Enduro. The 03 is an XC bike. handled it just fine. I did have a set of Azonic Outlaws on it though.

  21. #21
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    A transition makes a huge difference. If you can build up a bit of tranny, you shouldn't have any problems. Just don't land awkwardly. Ever.

  22. #22
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    Quote Originally Posted by weekendthrasher View Post
    Does anyone know of or have experience with 6-foot drops on a full suspension stumpy? I have a stock 2011 Stumpjumper Elite (full suspension with mini brain) and have been eyeing a 6-foot drop on my favourite trail, but don't want to find out the hard way whether or not the bike can handle it (so yes, this has to already assume that I can, haha). I've heard that 4-foot drops are okay, but don't know about 6-foot drops on it.

    As well, if this is a go (meaning wheels, forks, and frame can handle it), what's the set up most have used in terms of psi and or suspension settings?

    Appreciate any suggestions.
    If this is truly 6' to (essentially) flat, I would not do it on this bike. Yes, chances are it still look OK afterwards, but that is a lot of abuse for that bike at your weight. Most 6' drops people talk about doing are to a sloped tranny, and that makes all the difference in the world in terms of how hard the landing is.

    Also, a 6' drop measured with a tape measure is usually quite different from a 6' drop reported on the internet. I find most people drastically overestimate how big a drop is in actual feet. I think part of that is that drops look much higher from above, on top of your bike.
    15mm is a second-best solution to a problem that was already solved.

  23. #23
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    Gotta try the smaller jumps fiirst and work you're way up.

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    Quote Originally Posted by loggerhead View Post
    Gotta try the smaller jumps fiirst and work you're way up.
    I don't think it makes any difference to his bike.
    15mm is a second-best solution to a problem that was already solved.

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    thx for the feedback. have decided to take a pass on it. have no problem respecting the bike's limitations, still having tons of fun with other stuff (small jumps, technical rock climbs, wheelies up hills, etc.). maybe need to think about adding another bike down the road, but not willing to risk a pretty penny forcing this one to be something it just isn't. having too much fun with it for what it does do well, and right now i can live without the drop alot easier than i could live without the bike in one piece and functioning well.

    as for the drop, it is indeed actually 6 feet -- measured and signage in trail of such as well.

    again, thanks for the heads up. didn't trust what i was hearing in some bike shops that it would be fine, and this proves my reservations were well founded. guess is maybe they were looking to gain another sale ... if i broke my bike.

  26. #26
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    6 footer to flat is a big drop. I would do it to a downhill slope but not flat.

  27. #27
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    A lot of riders online have had frame cracks for the littlest things such as farting on their saddle and having it vibrate to their seat stay and cracking it.

    I say, just ride it off the 6ft to flat.
    Ragley Blue Pig

  28. #28
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    Quote Originally Posted by bquinn View Post
    4ft to flat is still fairly hard on a 5in bike...speed is your friend here!
    Your forward velocity has no effect on your downward velocity whatsoever in this situation. 1 mph or 100 mph, you land equally hard.


    Who wants to go 6 to flat anyway? What is this, 2001? Unless you are channeling your inner Macaskill or something I would get out the shovels and build a transition to land on. Avoid flat landings like the plague.

  29. #29
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    Quote Originally Posted by Blksocks View Post
    A lot of riders online have had frame cracks for the littlest things such as farting on their saddle and having it vibrate to their seat stay and cracking it.

    I say, just ride it off the 6ft to flat.
    Yeah, dental surgery isn't too expensive...
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  30. #30
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    6ft to a steep transition maaaaaybe... but 200lb guy 6ft to flat on a stumpy is going to end with broken chainstays or wheels (assuming u still have stock 28h on the front!).

    My friend has the same ride and it groans a lot on 4ft to flat even when he's pretty smooth.

    Basically the leverage ratio it too steep for big drops.

  31. #31
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    I've done plenty of drops of 3ft to flat on my 575. Not every day, but every so often. I've hit the "diving board" coming down Porcupine Rim in Moab a few times on my 575. That's a 4 footer to flat, or maybe even a very very slight uphill tranny. I come down like a ton of bricks on that one. Would never do it on my bike more than the once a year I go there. Maybe I'm just not smooth enough, lol.

    Still, 6 footer to flat.........? ...........on a Stumpy?..............No thanks. Then again, I wouldn't hit that on any bike. I have done a 5-6 footer to super steep tranny a few times on my bike. That was buttah

  32. #32
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    Quote Originally Posted by Pau11y View Post
    Yeah, dental surgery isn't too expensive...
    A mouth guard isn't that expensive!
    Ragley Blue Pig

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    Quote Originally Posted by Blksocks View Post
    A mouth guard isn't that expensive!
    Yeah smartass, go ride w/ one and let me know how it works out for you

    If you manage to keep that thing in your mouth, even riding DH non-competitively, then I'll believe this comment has some basis in cycling. Until then, jam up that crack and shut your pie-hole.
    Last edited by Pau11y; 08-19-2011 at 07:11 AM.
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  34. #34
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    The question is why?

    Drops to flats really just aren't fun at all unless you are some super smooth trials rider or just have something to prove. There definitely is a case to be made to try it once just to say you did it.

    The diving board on Porcupine Rim is indeed about 4ft high so it is nice to read the post above where it is accurately described. I ride a 6" moment and I am 210lbs so that drop pretty much bottoms my bike out. Not sure your Stumpy is up to repeated abuse like that - not to mention hitting a genuine 6 footer.

    As as side note on Measurements on the Interwebs - you really have to take those with a grain of salt. I regularly hit the "10 footer" at a local park. Even though everyone calls it that on these boards the honest truth is that it is about 5'- 6' to where your rear tire hits the transition. It might be 10' to the floor but the lander is huge and well groomed. You would have to seriously overshoot the lander to get more than a 6' vertical drop out of it.

  35. #35
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    6ft drop to flat (w/a flair thrown in) only if you're Danny Macaskill...make that 25-30ft to flat

  36. #36
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    Quote Originally Posted by Pau11y View Post
    Yeah smartass, go ride w/ one and let me know how it works out for you

    If you manage to keep that thing in your mouth, even riding DH non-competitively, then I'll believe this comment has some basis in cycling. Until then, jam up that crack and shut your pie-hole.
    Yea, because he's going to ride with a mouth piece the entire time and not at the point of hitting that 6ft drop to flat.

    Don't be so emotional
    Ragley Blue Pig

  37. #37
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    Quote Originally Posted by Pau11y View Post
    Yeah smartass, go ride w/ one and let me know how it works out for you

    If you manage to keep that thing in your mouth, even riding DH non-competitively, then I'll believe this comment has some basis in cycling. Until then, jam up that crack and shut your pie-hole.
    I think you are taking this exchange a tad too seriously.
    15mm is a second-best solution to a problem that was already solved.

  38. #38
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    Just go super fast. The faster you go off the drop, the less impact on the bike.

  39. #39
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    Quote Originally Posted by aliikane View Post
    Just go super fast. The faster you go off the drop, the less impact on the bike.
    Missed some physics classes did ya?
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    Quote Originally Posted by aliikane View Post
    Just go super fast. The faster you go off the drop, the less impact on the bike.
    Only if there is a descent where you land, then your landing speed is reduced cause your still going down at 1metre per second say if your going fast enough, you need a good 30degree bank to land on ideally.

    I did a unplanned 8 foot drop the once, 80degree down bank which had a chunk missing and vertical but transitioned back to 80degree so lovely and smooth.


    Slow down your rebound damping before attempting any drops, it stops the land then bounce into the air then crash which faster makes worse.

  41. #41
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    This one is easy. If you have to ask, on MTBR no less, you shouldn't do it.

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    or better yet dial in your high speed compression first cuz that'll be the energy your gonna tell your rebound to work with

  43. #43
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    Quote Originally Posted by aliikane View Post
    Just go super fast. The faster you go off the drop, the less impact on the bike.
    If the drop is to flat (as in level), then going faster will not lessen the impact.
    15mm is a second-best solution to a problem that was already solved.

  44. #44
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    Quote Originally Posted by Pau11y View Post
    Missed some physics classes did ya?
    When you go faster, your momentum increases in the direction you are going so it lessens the gravity drop factor. I used to skateboard a lot and dropping off a loading dock with speed would lessen the blow on your legs if you increase your speed. There is less compression on your legs. So when you land, its a much smoother landing and much easier on your knees and legs.

  45. #45
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    Quote Originally Posted by aliikane View Post
    When you go faster, your momentum increases in the direction you are going so it lessens the gravity drop factor. I used to skateboard a lot and dropping off a loading dock with speed would lessen the blow on your legs if you increase your speed. There is less compression on your legs. So when you land, its a much smoother landing and much easier on your knees and legs.
    Gravity will accelerate you at 9.8 m/s no matter what your launch speed is. You will impact the ground at a higher speed if you were to sprint off the drop vs rolling off it.

    The reason the landing feels smoother is because when you launch off at speed your landing angle is more slack, thus allowing the force to dissipate through pushing the bike forward and lessening the shock sensation. Where as a slow drop your bike will drop straight down and come to a near complete stop resulting in the harsh landing. (this does not mean all harsh landing are caused from this....)

  46. #46
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    Quote Originally Posted by aliikane View Post
    When you go faster, your momentum increases in the direction you are going so it lessens the gravity drop factor.
    If by "gravity drop factor" you mean downward speed when you reach the ground, no, it does not (assuming level take off and landing).

    I am not familiar enough with skateboarding to explain your experience, so I will take your word on what you say. However, I would be willing to bet the difference has to do with the techniques involved in launching/landing at speed vs a slow huck.

    There are also likely to be differences in the way one lands a slow vs high speed drop on a bike. I know I tend to land drops better (consistently) when I have some speed, but that is due to my being better able to control the fore/aft tilt of the bike, and beyond a certain speed (which is not that fast) it does not make a difference.
    15mm is a second-best solution to a problem that was already solved.

  47. #47
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    Wow, there is so much wrong in this thread. Why do people feel the need to pretend they are physicists, and then spout out crap that proves they obviously are not? It is OK to not know something, and just remain silent.

    This is the actual reason why going fast makes things easier. When you accelerate forward and off a drop, the earth's rotation increases proportionally to yours and its mass. Because the planet is not perfectly spherical, the ground actually moves away from you as you speed up, which is why the impact feels lighter the faster you go. This is just physics and facts, people.

    Watch an airplane take off. As it gets going faster and faster, it begins to look like it is lifting UP into the air. But what is actually doing is moving forward, and staying put vertically. It is actually the earth moving DOWN relative to the airplane that causes the airplane to "appear" as though it is flying.

  48. #48
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    Quote Originally Posted by fotu View Post
    Wow, there is so much wrong in this thread. Why do people feel the need to pretend they are physicists, and then spout out crap that proves they obviously are not? It is OK to not know something, and just remain silent.

    This is the actual reason why going fast makes things easier. When you accelerate forward and off a drop, the earth's rotation increases proportionally to yours and its mass. Because the planet is not perfectly spherical, the ground actually moves away from you as you speed up, which is why the impact feels lighter the faster you go. This is just physics and facts, people.

    Watch an airplane take off. As it gets going faster and faster, it begins to look like it is lifting UP into the air. But what is actually doing is moving forward, and staying put vertically. It is actually the earth moving DOWN relative to the airplane that causes the airplane to "appear" as though it is flying.
    Brilliance!^^^^^^
    15mm is a second-best solution to a problem that was already solved.

  49. #49
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    Quote Originally Posted by aliikane View Post
    When you go faster, your momentum increases in the direction you are going so it lessens the gravity drop factor. I used to skateboard a lot and dropping off a loading dock with speed would lessen the blow on your legs if you increase your speed. There is less compression on your legs. So when you land, its a much smoother landing and much easier on your knees and legs.
    2clue is more correct than your summary of why you "perceive" the force from landing impact is less. The force of your mass multiplied by 9.81 m/s^2 (or 32.2 ft/s^2) is entirely in the vertical component. You WILL feel this if you drop 6 ft while traveling at 1E6 mph, or if the ground all of a sudden vanished and you drop the same 6 ft. AND, in fact, if you introduce additional speed, the acceleration (deceleration as most would call it associating to slowing) of you slowing due to the friction (resistance force) of your wheels hitting the ground will only add to the purely vertical force from gravity. If you doubt what I say, Google "force vector diagram". This is Physics 101.
    The reason why you FEEL less impact at higher speed is because your attention is dealing w/ the higher speed...and the greater danger of the (hard) ground that's rushing past under you. That's it.

    **Now, when you read up on the force vector diagram, there is a magnitude of the horizontal resistance force (friction) where when calc'd w/ the vertical response force, will result in a total response force w/ an angle. Now if this angle so happens to be perfectly parallel w/ the impact angle of your fork w/ respect to the ground, then your suspension will experience 100% of the total response force and you WILL feel significantly less "spiking" of the impact due to compression damping (provided your fork is tuned correctly). But this is such a small window it is seldom hit.

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  50. #50
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    Quote Originally Posted by fotu View Post
    Wow, there is so much wrong in this thread. Why do people feel the need to pretend they are physicists, and then spout out crap that proves they obviously are not? It is OK to not know something, and just remain silent.

    This is the actual reason why going fast makes things easier. When you accelerate forward and off a drop, the earth's rotation increases proportionally to yours and its mass. Because the planet is not perfectly spherical, the ground actually moves away from you as you speed up, which is why the impact feels lighter the faster you go. This is just physics and facts, people.

    Watch an airplane take off. As it gets going faster and faster, it begins to look like it is lifting UP into the air. But what is actually doing is moving forward, and staying put vertically. It is actually the earth moving DOWN relative to the airplane that causes the airplane to "appear" as though it is flying.
    you can use this next time you're in the middle of a 390 in progress, yes?

  51. #51
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    Quote Originally Posted by Pau11y View Post
    2clue is more correct than your summary of why you "perceive" the force from landing impact is less. The force of your mass multiplied by 9.81 m/s^2 (or 32.2 ft/s^2) is entirely in the vertical component. You WILL feel this if you drop 6 ft while traveling at 1E6 mph, or if the ground all of a sudden vanished and you drop the same 6 ft. AND, in fact, if you introduce additional speed, the acceleration (deceleration as most would call it associating to slowing) of you slowing due to the friction (resistance force) of your wheels hitting the ground will only add to the purely vertical force from gravity. If you doubt what I say, Google "force vector diagram". This is Physics 101.
    The reason why you FEEL less impact at higher speed is because your attention is dealing w/ the higher speed...and the greater danger of the (hard) ground that's rushing past under you. That's it.

    **Now, when you read up on the force vector diagram, there is a magnitude of the horizontal resistance force (friction) where when calc'd w/ the vertical response force, will result in a total response force w/ an angle. Now if this angle so happens to be perfectly parallel w/ the impact angle of your fork w/ respect to the ground, then your suspension will experience 100% of the total response force and you WILL feel significantly less "spiking" of the impact due to compression damping (provided your fork is tuned correctly). But this is such a small window it is seldom hit.

    Science... it's real
    That response is over my head. Laymans terms. Are you a physicist?

    He is still saying something similar to me that the landing will be less harsh. That is my point. When you go faster your landing angle will be less thus resulting in less harsh impact on your bike and body.


    Look at this example: Impulse of Force

    In this example the speed is constant in the collision, however, the angle of the collision determines the force because of the change of velocity. Thus, since gravity is a constant, the speed you are dropping is the same. However, your angle of impact and change in velocity determines the force of the impact.

    To me, that is why car head on collisions with a wall are more dangerous than hitting a wall at an angle.
    Last edited by aliikane; 08-23-2011 at 09:18 AM.

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    Quote Originally Posted by fotu View Post
    Wow, there is so much wrong in this thread. Why do people feel the need to pretend they are physicists, and then spout out crap that proves they obviously are not? It is OK to not know something, and just remain silent.

    This is the actual reason why going fast makes things easier. When you accelerate forward and off a drop, the earth's rotation increases proportionally to yours and its mass. Because the planet is not perfectly spherical, the ground actually moves away from you as you speed up, which is why the impact feels lighter the faster you go. This is just physics and facts, people.

    Watch an airplane take off. As it gets going faster and faster, it begins to look like it is lifting UP into the air. But what is actually doing is moving forward, and staying put vertically. It is actually the earth moving DOWN relative to the airplane that causes the airplane to "appear" as though it is flying.
    futo,
    I see you posted this after mine so you most likely was not addressing my diatribe. So, in kind, I'll be kind.
    Your comparison of plane take-off speed vs what a guy riding a bike off a 6 ft drop is off by about a order of magnitude in velocities... A plane starts to experience lift at ~120 to 170 mph. You do drops somewhere between 10 to 20mph...for your everyday riders. AND, the delta in percent of Earth's rotational speed between your speed + Earth's rotational speed, and just Earth's rotational speed (even at delta^2) when used in calc of angular momentum is also insignificant (considering the Earth's rotational velocity is what...~730 mph.
    Your citation of the curvature of the Earth as experienced over 10 to 30 ft (dist you'd travel at speed dropping 6 ft) is SO infinitesimal it can be considered flat, considering the radius of the earth is what...~4000 miles?

    So, the effects you're talking about... at the scales we're evaluating, sorry, but bunk!

    AND, if you want another mind bender about scale, check out man-made global warming:
    From 1800 to present: CO2 increase went from ~300ppm to ~400ppm, or a total of ~33%. CO2 % in the atmosphere is ~ 0.04% (based from the 400ppm value). Thus 33% or ~100ppm of CO2 increase equate to ~ 0.0013% of CO2 increase over the span of ~200 years.
    O2 and N2 makes up about 27% and 68% of the atmosphere, respectively, but are completely non-factors for greenhouse effects...absorption/re-emit spectrum is out of the IR range, therefore no "heating".
    NOW, water vapor is ~ 4% of the atmosphere, or ~100 times the amount of CO2. Water vapor has ~ the same Cv and Cp of CO2 and re-emits ~ the same level of IR as CO2 from visible light.
    So comparing the two, if you tell me that the 0.0013% CO2 increase will be the driver behind runaway global warming, I'll say you're "crying wolf"!
    Last edited by Pau11y; 08-23-2011 at 09:22 AM.
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    Quote Originally Posted by Spartacus Rex View Post
    Drops to flats really just aren't fun at all unless you are some super smooth trials rider or just have something to prove. There definitely is a case to be made to try it once just to say you did it.
    I tried a 6 foot to flat once... It didn't end well.

    That was back in my trials days and I was on a Specialized Enduro Hardtail. I routinely did 3-4 feet to flat with the occasional 5 footer thrown in for good measure. Never went after the 6 foot mark again. The bike eventually developed a massive crack at the head tube/top tube junction. Now, 2 separated shoulders, 6 broken ribs, 6 broken vertebrae, one punctured lung and 2 kids later the most I do is 2-3 feet to flat, or 5-6 feet to a clean transition.

  54. #54
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    Quote Originally Posted by aliikane View Post
    That response is over my head. Laymans terms. Are you a physicist?

    He is still saying something similar to me that the landing will be less harsh. That is my point. When you go faster your landing angle will be less thus resulting in less harsh impact on your bike and body.


    Look at this example: Impulse of Force

    In this example the speed is constant in the collision, however, the angle of the collision determines the force because of the change of velocity. Thus, since gravity is a constant, the speed you are dropping is the same. However, your angle of impact and change in velocity determines the force of the impact.

    If I was to throw a rubber ball at the ground at a 90 degree angle and at the same speed throw it at a 30 degree angle the impact would be less and the ball would not bounce as high due to the greater change in velocity and impact will be less. That is why car head on collisions with a wall are more dangerous than if you ran into a wall at an angle.
    Alright, very good on the hyperphysics link
    But it broke down here: your vertical speed gained from the gravitational acceleration is completely separate from the horizontal speed...and there's nothing glancing about it. So, even tho your horizontal speed change is minimized as explained from Hyperphysics, by haulin' ass off the drop, your vertical speed change isn't and you'll still feel ALL of the 6ft drop.
    Think of it like this: a feather and lead ball drops the same rate in a vacuum, regardless of how fast you're moving sideways...vacuum is vacuum...no wind (air) resistance. If you want to be technical, on the solar system frame of reference, the Earth not only has a rotational velocity, but also a orbital velocity (around the sun), and yet the feather vs lead ball comparison still remains the same... My point, they're all separate...hence the vector force diagram...direction and magnitude matters. Now, they can sum to something greater of lesser. But when you decompose a force in a reaction, each is its own.

    And no, I'm not a physicist, I'm an electrical engineer. If you want a mind bender, look into electromagnetism. Newtonian physics (what we've been talking about) is quite "visible". Electromagnetism isn't. Worse yet, quantum physics!
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    Quote Originally Posted by Pau11y View Post
    futo,
    I see you posted this after mine so you most likely was not addressing my diatribe. So, in kind, I'll be kind.
    Your comparison of plane take-off speed vs what a guy riding a bike off a 6 ft drop is off by about a order of magnitude in velocities... A plane starts to experience lift at ~120 to 170 mph. You do drops somewhere between 10 to 20mph...for your everyday riders. AND, the delta in percent of Earth's rotational speed between your speed + Earth's rotational speed, and just Earth's rotational speed (even at delta^2) when used in calc of angular momentum is also insignificant (considering the Earth's rotational velocity is what...~730 mph.
    Your citation of the curvature of the Earth as experienced over 10 to 30 ft (dist you'd travel at speed dropping 6 ft) is SO infinitesimal it can be considered flat, considering the radius of the earth is what...~4000 miles?

    So, the effects you're talking about... at the scales we're evaluating, sorry, but bunk!
    Actually, even the plane example is bunk.

    But it goes with the point of his post.

    Which I think you missed.
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    Quote Originally Posted by kapusta View Post
    Actually, even the plane example is bunk.

    But it goes with the point of his post.

    Which I think you missed.
    He's talking about the plane leaving the surface of the Earth at a tangential trajectory... But you're right, I totally missed his point w/ that example; what's he talking about?
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    Quote Originally Posted by Pau11y View Post
    what's he talking about?
    I think post was intended as sarcastic humor.
    15mm is a second-best solution to a problem that was already solved.

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    I think somebody got trolled.

    Faster is not better. You can go too fast, and miss the transition all together. Buddy did this last week, and snapped his Canfield Jedi frame into two pieces!

    Me, I have to care for my disabled wife, so serious injuries are out of the question. 2-3 foot drops are my limit.

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    Quote Originally Posted by Bilirubin View Post
    I think somebody got trolled.

    Faster is not better. You can go too fast, and miss the transition all together. Buddy did this last week, and snapped his Canfield Jedi frame into two pieces!

    Me, I have to care for my disabled wife, so serious injuries are out of the question. 2-3 foot drops are my limit.
    Okay, I fed the troll... (face-palm)

    Hey, can you throw up pics of the broken Jedi?
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    You probably already got the info you wanted, but thought I would add my .02. On my last bike, an old-school Schwinn Mesa hardtail, I made hundreds of 3-4 foot drops of stairs, rocks, and ruts onto all kinds of terrain, including concrete, and the only thing to ever break was spokes and rims. IMHO, any bike should be able to handle drops like these, but when you up to 5-6 feet with a flat landing... you're pushing it!

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    Quote Originally Posted by Pau11y View Post
    futo,
    I see you posted this after mine so you most likely was not addressing my diatribe. So, in kind, I'll be kind.
    Your comparison of plane take-off speed vs what a guy riding a bike off a 6 ft drop is off by about a order of magnitude in velocities... A plane starts to experience lift at ~120 to 170 mph. You do drops somewhere between 10 to 20mph...for your everyday riders. AND, the delta in percent of Earth's rotational speed between your speed + Earth's rotational speed, and just Earth's rotational speed (even at delta^2) when used in calc of angular momentum is also insignificant (considering the Earth's rotational velocity is what...~730 mph.
    Your citation of the curvature of the Earth as experienced over 10 to 30 ft (dist you'd travel at speed dropping 6 ft) is SO infinitesimal it can be considered flat, considering the radius of the earth is what...~4000 miles?

    So, the effects you're talking about... at the scales we're evaluating, sorry, but bunk!

    AND, if you want another mind bender about scale, check out man-made global warming:
    From 1800 to present: CO2 increase went from ~300ppm to ~400ppm, or a total of ~33%. CO2 % in the atmosphere is ~ 0.04% (based from the 400ppm value). Thus 33% or ~100ppm of CO2 increase equate to ~ 0.0013% of CO2 increase over the span of ~200 years.
    O2 and N2 makes up about 27% and 68% of the atmosphere, respectively, but are completely non-factors for greenhouse effects...absorption/re-emit spectrum is out of the IR range, therefore no "heating".
    NOW, water vapor is ~ 4% of the atmosphere, or ~100 times the amount of CO2. Water vapor has ~ the same Cv and Cp of CO2 and re-emits ~ the same level of IR as CO2 from visible light.
    So comparing the two, if you tell me that the 0.0013% CO2 increase will be the driver behind runaway global warming, I'll say you're "crying wolf"!
    Ha, shows how much you know! I am impressed, you managed to make your entire post irrelevant just by making the post.

    You should probably stick to electrical engineering. First of all, where did I mention the curvature of the earth? Second of all, what does global warming have to do with it?

    To make a comparison about radiative forcing, you need to compare the impacts over the lifetime of the particle. How long does water vapor stay in the atmosphere? How long does CO2? Comparing the specific heat of two different materials is kind of irrelevant.

    Here you go, geek out on this.

    Oh but I forgot, the IPCC is a bunch of politically motivated shills. Not "scientists".

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    Suppose there is a magical runway that can somehow match the rolling speed of an airplane taking off....uhh, nevermind.
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    Quote Originally Posted by Pau11y View Post
    Hey, can you throw up pics of the broken Jedi?
    Would love to, but I only saw him driving his truck up to the exit of the trail to begin his long uphill climb to where he left the frame after doing it. He was still infuriated so I wasn't about to ask him to take pics. Will ask about though to see if any have appeared.

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    Quote Originally Posted by Pau11y View Post
    2clue is more correct than your summary of why you "perceive" the force from landing impact is less. The force of your mass multiplied by 9.81 m/s^2 (or 32.2 ft/s^2) is entirely in the vertical component. You WILL feel this if you drop 6 ft while traveling at 1E6 mph, or if the ground all of a sudden vanished and you drop the same 6 ft. AND, in fact, if you introduce additional speed, the acceleration (deceleration as most would call it associating to slowing) of you slowing due to the friction (resistance force) of your wheels hitting the ground will only add to the purely vertical force from gravity. If you doubt what I say, Google "force vector diagram". This is Physics 101.
    The reason why you FEEL less impact at higher speed is because your attention is dealing w/ the higher speed...and the greater danger of the (hard) ground that's rushing past under you. That's it.

    **Now, when you read up on the force vector diagram, there is a magnitude of the horizontal resistance force (friction) where when calc'd w/ the vertical response force, will result in a total response force w/ an angle. Now if this angle so happens to be perfectly parallel w/ the impact angle of your fork w/ respect to the ground, then your suspension will experience 100% of the total response force and you WILL feel significantly less "spiking" of the impact due to compression damping (provided your fork is tuned correctly). But this is such a small window it is seldom hit.

    Science... it's real

    This is SPOT on, allowing for a perfectly flat drop area, add in even a slight drop and faster will help slightly at first ofcourse.

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    Quote Originally Posted by fotu View Post
    Oh but I forgot, the IPCC is a bunch of politically motivated shills. Not "scientists".
    I can't read the tone of this statement...sarcasm...global warming proponent? Funny thing is no one is arguing this point, only the magnitude of the change w/ respect to man-made CO2.

    The climate thing...I just want to kick the hornet's nest...no other good reason

    As a power systems guy, the climate change guys' claims are impacting our field like a friggin' freight train! So yeah, I've started to look into the IPCC's claims.
    But for you to say Cp/Cv is "irrelevant"...seriously?! 1000 BTUs to change phase from vapor to liquid, and it's "irrelevant"?
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    Quote Originally Posted by Bilirubin View Post
    Would love to, but I only saw him driving his truck up to the exit of the trail to begin his long uphill climb to where he left the frame after doing it. He was still infuriated so I wasn't about to ask him to take pics. Will ask about though to see if any have appeared.
    Thanx! The reason is I ride a '11 Jedi...
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    Quote Originally Posted by Pau11y View Post
    I can't read the tone of this statement...sarcasm...global warming proponent? Funny thing is no one is arguing this point, only the magnitude of the change w/ respect to man-made CO2.

    The climate thing...I just want to kick the hornet's nest...no other good reason

    As a power systems guy, the climate change guys' claims are impacting our field like a friggin' freight train! So yeah, I've started to look into the IPCC's claims.
    But for you to say Cp/Cv is "irrelevant"...seriously?! 1000 BTUs to change phase from vapor to liquid, and it's "irrelevant"?
    Yeah, you are a little tone-deaf. But that's ok. Relevance is contextual, and in the case of global warming, comparing the specific heat of two materials and using that as a measure of radiative forcing is kind of missing the point. Or, irrelevant, in other words. Look, I am not a linguist. Read between the lines.

    And by the way, my airplane analogy makes implicit reference to newton's third law, not the tangential velocity with respect to the curvature of the earth. I was just killin some time. It was kind of supposed to be funny, I didn't think anyone would have thought I was trolling.

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    Quote Originally Posted by fotu View Post
    Yeah, you are a little tone-deaf. But that's ok. Relevance is contextual, and in the case of global warming, comparing the specific heat of two materials and using that as a measure of radiative forcing is kind of missing the point. Or, irrelevant, in other words. Look, I am not a linguist. Read between the lines.

    And by the way, my airplane analogy makes implicit reference to newton's third law, not the tangential velocity with respect to the curvature of the earth. I was just killin some time. It was kind of supposed to be funny, I didn't think anyone would have thought I was trolling.
    Calling me tone-deaf, then saying you're not a linguist...ouch!

    Cv/Cp irrelevance in that you have neither const P or const V...okay, I'll give you that. But when used to compare properties of water vapor and CO2 being equal, then comparing the quantities of both molecules involved in radiative forcing... Dood, 3 orders of magnitude between the delta for CO2 increase (arguably not all man-made) and the quantity of water in the atmosphere! AND, keep in mind 4% is an average value...

    BTW, thanx for the link to the IPCC's library. I've been meaning to get over there and d/l a full copy of the section where the climate model assumptions were enumerated... Supposedly NIPCC has done a good rebuking the IPCC model, paragraph for paragraph... Can't wait to check that out
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    Quote Originally Posted by Pau11y View Post
    Calling me tone-deaf, then saying you're not a linguist...ouch!

    Cv/Cp irrelevance in that you have neither const P or const V...okay, I'll give you that. But when used to compare properties of water vapor and CO2 being equal, then comparing the quantities of both molecules involved in radiative forcing... Dood, 3 orders of magnitude between the delta for CO2 increase (arguably not all man-made) and the quantity of water in the atmosphere! AND, keep in mind 4% is an average value...

    BTW, thanx for the link to the IPCC's library. I've been meaning to get over there and d/l a full copy of the section where the climate model assumptions were enumerated... Supposedly NIPCC has done a good rebuking the IPCC model, paragraph for paragraph... Can't wait to check that out
    I'd be interested in what you find. FYI, besides global warming skepticism, NIPCC founder Fred Singer has also made a name for himself by; denying the health risks of second hand smoke, and as a proponent of "free market environmentalism". I heard the Chinese are having great success with that approach.

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    Quote Originally Posted by fotu View Post
    I'd be interested in what you find. FYI, besides global warming skepticism, NIPCC founder Fred Singer has also made a name for himself by; denying the health risks of second hand smoke, and as a proponent of "free market environmentalism". I heard the Chinese are having great success with that approach.
    Can keep you posted on what I find.
    As for nations NOT heeding to environmentally sound methods of energy production...you'll never convert the thinking until quality of life reaches what they're seeing in the US. Period.

    Actually, this is where I have the largest issue w/ environmentalism...renewable energy is a 1st world nation solution to a questionable problem. As a power guy, there are only 2 MOs we follow: 1) cheap, 2)reliable, supply of energy (electricity). But we necessarily need to address emission problems that can impact the environment...NOX, SOX, particulates... But this 0.0013% CO2....that's a LOT to do over not so much. And in addressing this w/ renewable energy, we're jacking up the price of electricity to over 40% in just under 12 years! What will this do to the poor who are barely making ends meet right now? Do you think the developing nations would want to go wind/solar at $0.12 to $0.28 per kWh vs coal which costs $0.02 per kWh...AND, do we as a 1st world nation even have the right to say anything at them as we've puked all sorts of hell into the atmosphere when we went thru our industrial revolution.
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    right...except that China is kicking our ass in renewables development, so that argument kind of doesn't work.

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    Quote Originally Posted by fotu View Post
    right...except that China is kicking our ass in renewables development, so that argument kind of doesn't work.
    Yes it does. Even tho China's % growth is huge, and ours is small, the ACTUAL numbers are so severely lop-sided towards us that we're talking about magnitudes of diff in actual MWs.

    IE) our energy production from nuke is ~20%, and France's is ~87... But actual value in MW, we're like 300% that of France w/ our 20%.
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    Quote Originally Posted by Pau11y View Post
    Thanx! The reason is I ride a '11 Jedi...

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    Quote Originally Posted by Pau11y View Post
    Yes it does. Even tho China's % growth is huge, and ours is small, the ACTUAL numbers are so severely lop-sided towards us that we're talking about magnitudes of diff in actual MWs.

    IE) our energy production from nuke is ~20%, and France's is ~87... But actual value in MW, we're like 300% that of France w/ our 20%.
    Sorry, I meant China is kicking our ass in investment of renewables. As in dollars. A better indicator in their interest in investing in renewables (duh) than number of MW of capacity. So, no, your argument doesn't really work.

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    W...T...F???? I think I walked into the wrong thread.

    BTW, that broken Jedi, crazy!
    Gotta get up to get down.
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    Was off the drop below. In fact, since I took that picture the transition was extended another 10 feet. I can only imagine how fast he must have been going to overshoot all of it.

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    So drops to flat cause global warming?
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

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    Quote Originally Posted by Bilirubin View Post
    Was off the drop below. In fact, since I took that picture the transition was extended another 10 feet. I can only imagine how fast he must have been going to overshoot all of it.
    Yeah, you may have not had the pleasure of riding a Jedi...you don't slow down, anywhere! When I was talking to Chris about my warranty issue, he told me he had let some privateers take out some demo bikes. The all came back saying exactly what I said. Like when you roll it into chunder at speed, typically a bike will slow down as the rear hooks onto square edge hits. The Jedi doesn't. In fact, I think the way rear end moves, it pumps the bike as the spring unloads and you get a little kick!
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    Quote Originally Posted by Pau11y View Post
    Yeah, you may have not had the pleasure of riding a Jedi...you don't slow down, anywhere! When I was talking to Chris about my warranty issue, he told me he had let some privateers take out some demo bikes. The all came back saying exactly what I said. Like when you roll it into chunder at speed, typically a bike will slow down as the rear hooks onto square edge hits. The Jedi doesn't. In fact, I think the way rear end moves, it pumps the bike as the spring unloads and you get a little kick!
    That doesn't sound physical. Can you draw me a vector diagram?

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    Quote Originally Posted by weekendthrasher View Post
    thanks for the warnings, will pay heed.

    what about 4-foot drops to flat ground? could the stumpy take it or is that just an exaggeration? i bought it with the intention of abusing it, but not breaking it so still trying to figure out its real-life limitations rather than theoretical. i'm getting more interested in jumps now than i thought i would, but not looking to do any hero like stuff, just have some fun without breaking the bank again.
    I used to be a stumpy owner about 3 months ago, and I would take it off 4 foot drops to flat, but I also weigh 165lbs. The one time I did try a 6 footer it was to a slight decline and still the bike was not happy there was complete bottom out! That was the last time I took it over that height. As my riding style changed and I was wanting to hit not if the bigger drops and jumps I decided to get a Bigger all mountain bike the Banshee Rune and it just loves those drops!!!!

  81. #81
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    Quote Originally Posted by trailville View Post
    So drops to flat cause global warming?
    no. only flat drops do.However, drops to flat actually occur much heavier in one part of our planet. So much so that it is causing a slight reversal in the planet's rotation, effectively turning back the effects of global warming and aging.

  82. #82
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    Quote Originally Posted by 53119 View Post
    no. only flat drops do.However, drops to flat actually occur much heavier in one part of our planet. So much so that it is causing a slight reversal in the planet's rotation, effectively turning back the effects of global warming and aging.
    Exactly! That is why it is so vitally important to get some good speed going before you hit the drop!

  83. #83
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    Quote Originally Posted by fotu View Post
    Exactly! That is why it is so vitally important to get some good speed going before you hit the drop!
    So then during the Galactic Alignment, when gravity has been cancelled on the galaxy center side of the planet by the effects of the super-massive black hole in its center, will we then be able to achieve tangential lift with all that additional speed?
    Naysayers never apologize. Critics go to their grave thinking everyone else is wrong.
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  84. #84
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    Quote Originally Posted by fotu View Post
    That doesn't sound physical. Can you draw me a vector diagram?
    Here's a force vector diagram for you... a Jedi w/ kick:
    Naysayers never apologize. Critics go to their grave thinking everyone else is wrong.
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  85. #85
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    you were doing so well Pau11y then you had to combine norris with a jedi?

    clearly overthinking you are. clearly more force with you than kung fu.

  86. #86
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    Quote Originally Posted by 53119 View Post
    you were doing so well Pau11y then you had to combine norris with a jedi?

    clearly overthinking you are. clearly more force with you than kung fu.
    Did you just make fun of Norris?

    DOOD! Duck!

    Edit: but with respect to the association of the Force to Kung-Fu, THIS guy is the Yoda!
    Naysayers never apologize. Critics go to their grave thinking everyone else is wrong.
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  87. #87
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    you made fun of Chuck. you put his head on a jedi! as if to say he needs another skill set to kick ass!he doesn't need morphing into any other, brother! spinning roundhouse to your manparts.

    we all know & agree that chuck can drop 6,8,10 to flat all day though, right? so the thread is solved. op, if you ain't chuck do not send it. we've done good here.
    and yes bruce lee owns Colt!
    Last edited by 53119; 08-24-2011 at 12:50 PM.

  88. #88
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    Quote Originally Posted by Pau11y View Post
    So then during the Galactic Alignment, when gravity has been cancelled on the galaxy center side of the planet by the effects of the super-massive black hole in its center, will we then be able to achieve tangential lift with all that additional speed?
    WTF are you talking about??? Tangential lift? Black holes? You sound like a total kook. Nice job getting some of these plebes to believe you know what you are talking about with your "vector diagrams" and your "orders of magnitude". What a hack job. Why don't you quit pretending to be a physicist and get back to work discrediting climatologists?

  89. #89
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    I can't believe people are still taking this thread seriously.
    Gotta get up to get down.
    LMB

  90. #90
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    Quote Originally Posted by fotu View Post
    WTF are you talking about??? Tangential lift? Black holes? You sound like a total kook. Nice job getting some of these plebes to believe you know what you are talking about with your "vector diagrams" and your "orders of magnitude". What a hack job. Why don't you quit pretending to be a physicist and get back to work discrediting climatologists?
    HAHAHA
    Even if you said you weren't trolling w/ the plane, I was w/ the Galactic Alignment
    But the force vector diagram...I didn't invent it... And, if you want to argue w/ it, contact Georgia State University...hyperphysics page authoring entity.
    Naysayers never apologize. Critics go to their grave thinking everyone else is wrong.
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    Maybe if your frame / body is the right shape, going faster acts as a wing and generates lift which reduced your rate of descent much like a glider.

    Try it over a fire and see if the thermal up draft will enable you to actually circle within it and gain some height.


    just incase

  92. #92
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    Quote Originally Posted by 53119 View Post
    no. only flat drops do.However, drops to flat actually occur much heavier in one part of our planet. So much so that it is causing a slight reversal in the planet's rotation, effectively turning back the effects of global warming and aging.
    No, its hard braking that creates problems with the earth's rotation. That's why whenever you are forced into a hard brake, you should then turn around and go real fast in the other direction and do another hard brake to set things right. I'm pretty sure that's in the IMBA handbook.
    A hard drop to flat though can actually knock the earth slightly out of orbit. It's very small, but they do add up over time. Fortunately there are a lot of Aussies doing drops on the opposite side of the planet to help offset the ones we do in the States.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  93. #93
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    "Try it over a fire and see if the thermal up draft will enable you to actually circle within it and gain some height."


    tried over a campfire with a pitbike after some pints of a nice brew....epic bunny hop fail.. stacked and roasted but able to piss the fire out at the same time!

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    I say just do it, buddy of mine rides cheap hard tail Novara bike he got from REI and his crazy ass hits 4-6 drops to almost flat quite often and it's still in one piece. If you are first owner and the frame cracks isn't their a lifetime warranty anyway?

  95. #95
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    Quote Originally Posted by REDMASTA View Post
    I say just do it, buddy of mine rides cheap hard tail Novara bike he got from REI and his crazy ass hits 4-6 drops to almost flat quite often and it's still in one piece. If you are first owner and the frame cracks isn't their a lifetime warranty anyway?
    They will deny the claim if the bicycle frame breaks where there was no structural defect such as the tubing ending up too narrow or poor weld. Most bicycle company do not warranty the rear-triangle which contains the chainstays(the items breaking most often).

  96. #96
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    I say after reading all this nerding ***** up talk we need to pass out a couple 20 sided die for a few folks here. I say you go ahead and hit it, before 2012 comes................oh great i started something there.

  97. #97
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    How about a 4-5' huck to a slight uphill on a hardtail XC bike into really soft dirt?

    Notice the crater marks from where my tires touched down.

    <iframe src="http://player.vimeo.com/video/18139117?title=0&amp;byline=0&amp;portrait=0" width="720" height="405" frameborder="0"></iframe><p><a href="http://vimeo.com/18139117">Sycamore Canyon (Huck Fail)</a> from <a href="http://vimeo.com/varaxis">Varaxis</a> on <a href="http://vimeo.com">Vimeo</a>.</p>

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    I had a tire grip issue ( 2.25 Nic's suck ) over some rocks tonight got knocked off line and hastily decided to take a 1' drop or crash, landed front wheel first bottomed out my forks then got pogo'd and just about managed to stop on and stop before a downed tree, CLOSE!!

    So my advice on a 6' drop is DON'T DO IT it's going to hurt if not first time, not far after.

  99. #99
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    Quote Originally Posted by Turveyd View Post
    I had a tire grip issue ( 2.25 Nic's suck ) over some rocks tonight got knocked off line and hastily decided to take a 1' drop or crash, landed front wheel first bottomed out my forks then got pogo'd and just about managed to stop on and stop before a downed tree, CLOSE!!

    So my advice on a 6' drop is DON'T DO IT it's going to hurt if not first time, not far after.
    I AGREE! After hearing that you ate **** on a 1' curb I am going to abstain from all six footers.

  100. #100
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    Quote Originally Posted by Varaxis View Post
    How about a 4-5' huck to a slight uphill on a hardtail XC bike into really soft dirt?

    Notice the crater marks from where my tires touched down.

    <iframe src="http://player.vimeo.com/video/18139117?title=0&amp;byline=0&amp;portrait=0" width="720" height="405" frameborder="0"></iframe><p><a href="http://vimeo.com/18139117">Sycamore Canyon (Huck Fail)</a> from <a href="http://vimeo.com/varaxis">Varaxis</a> on <a href="http://vimeo.com">Vimeo</a>.</p>
    fyi, hucks are measured by verticle drop, not horizontal distance. Usually from the lip to the top of the landing. That;s about 10". just sayin.

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