Dropping to flats?- Mtbr.com
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  1. #1
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    Dropping to flats?

    With a 14 inch combined travel bike how far should I worry about dropping to a flat? When does it become dangerous to the bike?

  2. #2
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    just be smooth or dont do it

  3. #3
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    Quote Originally Posted by vardiel
    just be smooth or dont do it
    But is there a limit?

  4. #4
    izumusx988
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    i wouldnt do anything over 4 feet

  5. #5
    No longer riding a haro!
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    When you have broken your frame/bike, you've passed your limit. You cannot say a definate limit, there are way to many factors.
    If you're not living on the edge you're taking up to much space.

  6. #6
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    Any numbers at all?

  7. #7
    e.f.f.e.c.t smoothoperatr
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    with a flat, all your energy and enertia mostly stops when you land on the flat spot cause your going straight down. with a landing, your bike " swings" with the landing and not as much stress is made. i hope i dont sound like a total dousch. its hard to explain

  8. #8
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    So a 6 ft drop off my roof straight into the back yard be a foolish thing to do on a Gemini 900 w/ Dorado fork?

  9. #9
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    Quote Originally Posted by Lickqid
    So a 6 ft drop off my roof straight into the back yard be a foolish thing to do on a Gemini 900 w/ Dorado fork?
    very much so.....plus you might crack the carbon fiber on the Dorado
    the trick is ENJOYING YOUR LIFE EACH DAY, don't waste them away wishing for better days

  10. #10
    e.f.f.e.c.t smoothoperatr
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    i did a 7 foot flat to flat/ concrete with my profile racing dr1. the only reason why i did it because the frame was strong as hell, steel swingarm and the frame was 15lbs. and it jolted my head fowards i almost hit the bars

  11. #11
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    If u kno wut ur doing and can land in your center of gravity on the rear wheel u can go pretty big but it takes time to get it perfected.

  12. #12
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    Nice, any ideas for any other backyard stunts I could build and screw around on? I live four hours away from the nearest FR/DH course, plus with school I don't get much time to bike like that.

  13. #13
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    Seriously? I'll put up another post about the stunts as well.

  14. #14
    Portland, OR
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    yea, it isnt a good idea to go to flat. it isnt the suspension that matters, it is your hubs, cranks ETC.

  15. #15
    Juanjo
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    In the past I've done a few drops to flat and I can say that the "limit" is way over 6,7 or 8 fts. but still is better to drop to tranny...
    ~~~~~~~~~~~~~~~~~~ \m/>-<\m/ ~~~~~~~~~~~~~~~~
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  16. #16
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    Quote Originally Posted by EastCoastHucker
    In the past I've done a few drops to flat and I can say that the "limit" is way over 6,7 or 8 fts. but still is better to drop to tranny...
    need the transitition....smoothinicity
    the trick is ENJOYING YOUR LIFE EACH DAY, don't waste them away wishing for better days

  17. #17
    Chinky on a Stinky
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    Quote Originally Posted by themarsvolta55
    with a flat, all your energy and enertia mostly stops when you land on the flat spot cause your going straight down. with a landing, your bike " swings" with the landing and not as much stress is made. i hope i dont sound like a total dousch. its hard to explain
    not that hard. with dropping to flat, the force of you dropping is suddenly stopped, with dropping to tranny, the force of u dropping is gradually stopped. thats y people die if they jump from a 10 story building onto cement rather than into water..............
    Straight outta Compton..............

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  18. #18
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    Quote Originally Posted by Chikity China
    not that hard. with dropping to flat, the force of you dropping is suddenly stopped, with dropping to tranny, the force of u dropping is gradually stopped. thats y people die if they jump from a 10 story building onto cement rather than into water..............
    at 10 stories people start dieing hitting water
    the trick is ENJOYING YOUR LIFE EACH DAY, don't waste them away wishing for better days

  19. #19
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    [QUOTE=Lickqid]Any numbers at all?[/QUOTE

    ...58
    Bart with $10,000 we'd be millionares. We could buy all sorts of valuable things...like love.

  20. #20
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    8.746 feet exactly

  21. #21
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    doRpzoRs to flatS rule my world. I'm after teh world record

  22. #22
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    Quote Originally Posted by Chikity China
    u get the idea................
    no I don't....at that height water is like the ground
    the trick is ENJOYING YOUR LIFE EACH DAY, don't waste them away wishing for better days

  23. #23
    Chinky on a Stinky
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    Quote Originally Posted by SHIVER ME TIMBERS
    at 10 stories people start dieing hitting water
    u get the idea................
    Straight outta Compton..............

    Team Tony Train - FR/DH Forever!!!!
    Sponsors: White Devil Syndicate (we're workin on it 'aight?)

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  24. #24
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    I did a six footer on my Faith 1 to flat and that's the biggest i would go to flat. Trannys are soooo much smoother.

  25. #25
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    I do up to 6 foot drops to flat on my HT.... but I land extra back tire heavy (like a trails rider) and I only use about 1 inch of my fork.... its SUPER smooth... but after doing it enough my upper crown comes loose from all the pull...
    Jake
    Yeti 303 WC 25th

    Quote Originally Posted by Dwight Moody
    Didn't you read the sticker on that shock? It said not to do whatever you did.

  26. #26
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    I did a 8 foot drop to flat on my Demo 8 but it wasn't bad at all because I was going as fast as I could. It was a 15 stair gap to flat. Dropping 5 feet to flat going 5 mph is going to be a lot harder on the bike than going 20 mph. Keep that in mind.
    Ridin' the streets of C-P-T in N-O-V-A

  27. #27
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    Any drop can be dangerous to the bike. The question is how high of a drop can YOU succesfully and safely pull off. Drops to flat help keep the parts market busy though, so by all means, push the limits.....

  28. #28
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    Quote Originally Posted by pntballpunk51
    I did a 8 foot drop to flat on my Demo 8 but it wasn't bad at all because I was going as fast as I could. It was a 15 stair gap to flat. Dropping 5 feet to flat going 5 mph is going to be a lot harder on the bike than going 20 mph. Keep that in mind.
    In a vaccuum, a bullet fired from a gun will hit the ground in exactly the same amount of time as a bullet dropped out of your hand, as long as they start out at the same height.

    But it does sorta feel smoother to land a jump when you're going fast. Why is this? WHY!? WHY!!!??? You can't possibly be falling at slower rate! Confused, need sleep... 6:15am ride today, bad idea...
    now the world is gone i'm just o n e

  29. #29
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    Quote Originally Posted by BontyRider
    But it does sorta feel smoother to land a jump when you're going fast. Why is this? WHY!? WHY!!!??? You can't possibly be falling at slower rate!
    because rather than going straight down you are falling at an angle, therefor making the impact less harsh.... Its kinda common sence...
    Like if you went off a 20 foot to flat at 100mph it would feel like a 2 foot to flat going 5mph...
    Jake
    Yeti 303 WC 25th

    Quote Originally Posted by Dwight Moody
    Didn't you read the sticker on that shock? It said not to do whatever you did.

  30. #30
    Just Ride
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    i did 12 stairs to flat (5 - 6ft) when i got my first 'real' bike. hardtail marin quake, put a big ass flat spot in my wheel, and bashed my nads on my seat. highest ive done since then is like 4 but it was a big ol gap.

  31. #31
    pedalphile
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    Quote Originally Posted by [email protected]
    because rather than going straight down you are falling at an angle, therefor making the impact less harsh.... Its kinda common sence...
    Like if you went off a 20 foot to flat at 100mph it would feel like a 2 foot to flat going 5mph...
    But that's not actually true. You're still falling at the same rate.
    now the world is gone i'm just o n e

  32. #32
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    Quote Originally Posted by BontyRider
    But that's not actually true. You're still falling at the same rate.
    not true numbers but it feels smoother
    the trick is ENJOYING YOUR LIFE EACH DAY, don't waste them away wishing for better days

  33. #33
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    ghetto landings

    Quote Originally Posted by Lickqid
    So a 6 ft drop off my roof straight into the back yard be a foolish thing to do on a Gemini 900 w/ Dorado fork?
    If you still have a warranty, go for it! It will usually take breaking a bike part to turn off riders to the idea of dropping to flat(at least for me(and i still do it sometimes)). If you wanna avoid that though i'd suggest making a little landing out of a small board even about 3ft long and however wide your comftorble with propped under a log.Thats what i do now and even though it doesn't sound like much of a tranny, you'd be surprised at the difference it makes.

  34. #34
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    Quote Originally Posted by SHIVER ME TIMBERS
    not true numbers but it feels smoother
    If you drop to flat, the force the ground exerts on you to stop you is directed straight up (definition of a drop to flat, no?). That means you stop dead, and all the energy you gained from falling is absorbed by the frame and rider.

    If you drop to tranny, the force the ground exerts is not directed straight up, it's directed perpendicular to the ground (so at some angle less than 90* to horizontal). so some of that force will act to push the bike horizontally, i.e., some of the energy you gained is used to accelerate you in the horizontal direction.

    a really simple model of course, but that's the basic physics. makes sense to me.
    That's not flying, that's falling with style!

  35. #35
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    Quote Originally Posted by BontyRider
    In a vaccuum, a bullet fired from a gun will hit the ground in exactly the same amount of time as a bullet dropped out of your hand, as long as they start out at the same height.

    But it does sorta feel smoother to land a jump when you're going fast. Why is this? WHY!? WHY!!!??? You can't possibly be falling at slower rate! Confused, need sleep... 6:15am ride today, bad idea...
    you always fall at the same rate, it's true. i blame momentum: if you're going faster you have more of it, but the force at the ground stays the same. so your momentum change from landing is the same, but compared to going slow, the change is a smaller proportion of your total momentum. that's my suspicion anyway.
    That's not flying, that's falling with style!

  36. #36
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    ... and if we just ...

    Quote Originally Posted by Grettiron
    you always fall at the same rate, it's true. i blame momentum: if you're going faster you have more of it, but the force at the ground stays the same. so your momentum change from landing is the same, but compared to going slow, the change is a smaller proportion of your total momentum. that's my suspicion anyway.
    Hmmm... maybe you're right. It's just an illusion because your body doesn't feel like it has stopped as suddenly; you're still moving.

    By extension, according to my sophisticated calculations, if you were to ride really fast off a ledge and simultaneously hit the ground and a brick wall, it would probably feel very very bad. Just a theory though.
    now the world is gone i'm just o n e

  37. #37
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    i did a 7 foot drop on my trek liquid 30. It took it a little rough, but ok. I dont know y u guys worry about to flat so much. i had a sport mart bike and the frame didnt break till i did a 5-6 foot drop.

  38. #38
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    How to calculate a drop to flat, 2 methods:

    1. Post this crap on Pinkbike.
    2. Get a ruler, 12 inches or longer, put it in your left hand and slap yourself on your forehead with it.

  39. #39
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    I see

  40. #40
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    i did a 7 foot to flat on a rigid trials bike... somewhat small actually
    pay me

  41. #41
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    Quote Originally Posted by Inconsiderate Dan
    How to calculate a drop to flat, 2 methods:

    1. Post this crap on Pinkbike.
    2. Get a ruler, 12 inches or longer, put it in your left hand and slap yourself on your forehead with it.
    Drops to flat are fun if you know how to do them right....
    Jake
    Yeti 303 WC 25th

    Quote Originally Posted by Dwight Moody
    Didn't you read the sticker on that shock? It said not to do whatever you did.

  42. #42
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    Quote Originally Posted by vardiel
    just be smooth or dont do it
    there is no such thing as smooth on a drop to flat

  43. #43
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    Quote Originally Posted by jazzy jibber
    there is no such thing as smooth on a drop to flat
    please tell me you are joking?
    Jake
    Yeti 303 WC 25th

    Quote Originally Posted by Dwight Moody
    Didn't you read the sticker on that shock? It said not to do whatever you did.

  44. #44
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    Quote Originally Posted by [email protected]
    please tell me you are joking?
    drops to flat are not something to be joked about. They need to be taken seriously.

  45. #45
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    very much so...

    Quote Originally Posted by zachdank
    drops to flat are not something to be joked about. They need to be taken seriously.
    I regularly do drops to flat. just yesterday i did a 5 footer off a loading dock. flat spot in my 321 rims but w/e.... i do notice a difference in techique on a hardtail vs. a DS.
    Hardtail(which i prefer) is more weight on the rear. come down on rear wheel, and ease weight onto front. DS can be much more centered over bike. infact, its almost harder to trials drop on a DS b/c of the way teh suspension moves...
    Im just saying..

  46. #46
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    Here's what I think a bike can handle safely when dropping to flat (roughly):

    If you have no/little style so you're basically landing flat:
    XC bike - 3 feet
    AM bike - 4 feet
    FR bike - 5-6 feet

    After this you're gonna start bending/breaking things like rims, handlebars, hubs etc

    If you have mad style and are super smooth:
    XC bike - 6 feet (don't try it)
    AM bike - 7/8 feet
    FR bike - 8-10 feet but by this height the consequences are high and you'll need to land it very nicely or you'll break something.

  47. #47
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    Look at the drop...If you feel good about it, then do it.
    If it makes you want to poop, then don't.
    If something breaks on either your bike or your body, you chose poorly.

  48. #48
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    Drops to flat are silly and pointless (IMHO) - However, drops top flat on a fully, ESPECIALLY a long travel/DH/FR Bike, are REALLY stupid and REALLY bad for equipment. You can go MUCH bigger and MUCH smoother on an HT to flat - as stated above - landing on back wheel and smoothing it out. I *OCCASIONALLY* will still do up to 7 ft this way, and have seen trials riders to 10-12 smooth and Silently.

    On a fully you depen on your suspension and you have a good chance at blowing dampers, AND if you try to go to the back wheel A La HT - you load up the suspension/linkages in a way they are absolutely not meant to be loaded making the move hard and REALLY bad for your bike.



    Whether drops to flat are good or bad, fun or not - is a matter of opinion. That it is abusive and hard on equipment is fact; that it doesnt require much skill (unless you are successfully landing big drops smooth and quiet) I would venture to call fact as well!

  49. #49
    [email protected] NYC Freerider
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    Quote Originally Posted by EastCoastHucker
    In the past I've done a few drops to flat and I can say that the "limit" is way over 6,7 or 8 fts. but still is better to drop to tranny...
    Hahahahaha....yeah, like that 20ft stair gap you over-shot. 20ft to flat! I think its safe to say that the faster you go off the drop to flat, the less harsh the impact...please correct me if im wrong.
    Last edited by Master_Jako; 08-31-2005 at 08:20 AM.

  50. #50
    Juanjo
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    Quote Originally Posted by Master_Jako
    Hahahahaha....yeah, like that 20ft stair gap you over-shot. 20ft to flat! I think its safe to say that the faster you go off the drop to flat, the less harsh the impact...please correct me if im wrong.
    IMO u r RIGHT .

    but the only way u can do a 20 to flat is by mistake
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  51. #51
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    Quote Originally Posted by EastCoastHucker
    IMO u r RIGHT .

    but the only way u can do a 20 to flat is by mistake

    "C" cause you wouldn't want to do it
    the trick is ENJOYING YOUR LIFE EACH DAY, don't waste them away wishing for better days

  52. #52
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    Quote Originally Posted by [email protected]
    Like if you went off a 20 foot to flat at 100mph it would feel like a 2 foot to flat going 5mph...
    Anyone who passed grade 11 physics would know that this is just plain wrong!

    Kn.
    I used to be with it. Then, they changed what "it" is, and now what I'm with is no longer "it". And whatever "it" is, is strange and confusing.

  53. #53
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    Quote Originally Posted by BontyRider
    In a vaccuum, a bullet fired from a gun will hit the ground in exactly the same amount of time as a bullet dropped out of your hand, as long as they start out at the same height.

    But it does sorta feel smoother to land a jump when you're going fast. Why is this? WHY!? WHY!!!??? You can't possibly be falling at slower rate! Confused, need sleep... 6:15am ride today, bad idea...
    That's hilarious! Too bad it isn't true. Just because air resistance doesn't exist in a vaccuum, doesn't mean energy doesn't. For every action, there is an equal but opposite reaction, even in a vaccuum. To say otherwise would mean that if you fired the bullet, pointing it upwards instead, that it would stay in the chamber. How would that be? Would the gun blow up in your hand instead? No, because the fragments of the gun would have to wait for gravity to pull them down with the other bullet you just let go of from your hand. Then you would be unable to shoot anybody in a vaccuum. Then the banks would all be turned into vaccuums to prevent robbery.

    In a vaccuum, on earth, with earth's gravity, you could huck off of a 100 foot to flat drop, and you would still die.

    If you hit a drop to flat with more speed, it is just like hitting a drop with at least some degree of tranny, because your energy is being directed into the ground at an angle, whereas if it did the drop slowly, your energy would be directed more directly into the ground.

    What does it all boil down to? Two things:

    1. don't worry about having to wear an oxygen mask to go to the bank in the future.
    2. drops to flat are ghetto.
    3. dwarves riding big bikes is a bizzare thing.
    This election is like a turd in a bag on your porch... whether its a blue bag or a red bag, it's still a turd on your porch.

  54. #54
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    Quote Originally Posted by BontyRider
    In a vaccuum, a bullet fired from a gun will hit the ground in exactly the same amount of time as a bullet dropped out of your hand, as long as they start out at the same height.

    But it does sorta feel smoother to land a jump when you're going fast. Why is this? WHY!? WHY!!!??? You can't possibly be falling at slower rate! Confused, need sleep... 6:15am ride today, bad idea...

    well, when your wheels are spinning like that, your landing force is distributed around the wheel, instead of at just one point. so its much easier on the wheel.

  55. #55
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    Quote Originally Posted by Ohio_Huck
    well, when your wheels are spinning like that, your landing force is distributed around the wheel, instead of at just one point. so its much easier on the wheel.
    That almost doesn't make sense

  56. #56
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    I like to ride my bike.

    Physics makes my bike go
    Last edited by biketiger; 09-02-2005 at 02:08 PM. Reason: I'm stupid

  57. #57
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    i did 6 and a friend did the same on a jamis hard tail
    I HATE WORK, WORK IS BAD, WORK = NO BIKE, NO BIKE = NO GOOD

  58. #58
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    Quote Originally Posted by vpjackal989
    i wouldnt do anything over 4 feet
    I did 5 feet to flat on my HT.
    120 mm. fork.

  59. #59
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    Quote Originally Posted by K'Endo
    Anyone who passed grade 11 physics would know that this is just plain wrong!

    Kn.
    not exact numbers, but go do a say 3 foot to flat at about 5mph or less, then do the same one at 20+mph.... feel the difference? alot smoother going faster...
    Jake
    Yeti 303 WC 25th

    Quote Originally Posted by Dwight Moody
    Didn't you read the sticker on that shock? It said not to do whatever you did.

  60. #60
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    Quote Originally Posted by pntballpunk51
    I did a 8 foot drop to flat on my Demo 8 but it wasn't bad at all because I was going as fast as I could. It was a 15 stair gap to flat. Dropping 5 feet to flat going 5 mph is going to be a lot harder on the bike than going 20 mph. Keep that in mind.
    If you have a gun that is perfectly horizontal and fire it and drop a simmilar bullet from the same level which bullet will hit the ground first? They both will hit at the same time. I know it sounds weird but its physics. I could be wrong, but I dont think speed is going to change how hard a drop to flat is.
    If I want your opinion, I will give give it to you...

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    -insert stupid comment here-
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  62. #62
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    The straight dope on bullets being fired from guns...

    http://www.straightdope.com/classics/a5_201a.html

  63. #63
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    Quote Originally Posted by Mountainbikextremist
    If you have a gun that is perfectly horizontal and fire it and drop a simmilar bullet from the same level which bullet will hit the ground first? They both will hit at the same time. I know it sounds weird but its physics. I could be wrong, but I dont think speed is going to change how hard a drop to flat is.
    No, a bullet from a gun is given a bunch of momentum by the explosion of the gun powder, while a dropped bullet would only have the momentum given it by gravity. The fired bullet would have the speed of gravity <i>plus</i> the speed from being fired.

    Now if you had a parachute that weighed as much as your bullet and you dropped them both in a vaccum, they would both hit as the same time.

    As for landing drops to flat, the faster you are going are going, the more of your momentum goes forward rather than up. You have more force, it just less total force gets sent up into your bike.

    EDIT: OH, the gun isn't pointed at the ground? That's different. If the gun is perpendicular to the gravitational center, then yes, it does hit the ground at the same time.
    Last edited by Dwight Moody; 09-16-2005 at 11:29 AM.
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    Wow, I've lost a lot of respect for a lot of members of this forum. I can't believe how many people out there believe that hitting a drop to flat with speed is somehow less of an impact then if you just slowly wheelie off. This is such basic physics.

    Here's the real deal:

    The milli-second you leave the lip of the drop your bike starts accelerating down at roughly 30 feet per second (9.8 meters per second exactly). Assuming a level drop (no lip) you are would be moving downwards at zero feet per second and after one second of dropping you would be falling 30 feet per second. You average speed is halfway between these two numbers as your acceleration is basically linear. So for that 1 second you averaged 15 feet/second thus you dropped 15 feet roughly. On huge drops wind resistance matters but not much any anything 99% of people ride.

    The point in me explaining this all is that there is really 2 components to your speed. There is the speed you are travelling forward/backward and the speed you are travelling up/down. If, for example, you are riding up a 30 degree hill at X speed, you are really moving forward at Y speed and upwards at Z speed which when combined give you an 30 degree upwards vector (motion).

    Lets use a 15 footer drop to flat as an example because that works out nice for the calculations. Lets say a rider named Jon sales off our drop to flat at 10 feet per second forward. When he leaves the drop he is moving at 10 feet per second forward and 0 ft/sec down. One second later Jon will touch down (as previously explained that you drop 15 feet in the first second of dropping and our drop is 15 ft) and he will be travelling 30 f/s down and still 10 f/s forward (minus wind resistance).

    When he hits the ground the up/down component of his speed is reduced completely to zero because the up/down speed component is perfectly perpendicular to the landing. The landing bounces him straight back up (although shocks minimize this). While this is all going on the 10 feet per second of forward speed continues undimished because he has not run into anything to slow this speed component down. As a result, the bounce straight back up from the direct impact is masked because the 10 f/s of forward speed remains which means the angle you bounce is not actually straight up but forward too as the forward speed component remains. Had you not been flying off the drop but rather you basically fell off you'd hit the ground just as hard and bounce up again just as quickly except the forward speed wouldn't be there to hide the direct impact your up/down speed just had with the ground.

    In summary this is the main reason why people think speed helps:

    Your forward speed component masks your upward bounce so you still bounce upwards just as hard but you're also moving forward which gives the illusion that the ground somehow transferred your dropping speed to forward speed when in reality, you had the forward speed the whole time and all you up/down speed was used up running into the ground. When you actually hit a tranny you can come in with no forward speed yet you will bounce up and forward because the sloped landing converts some of your downward speed to forward speed and thus isn't part of the 'hit'.

    People think drops to flat are smoother with speed because you come out of the drop with speed (the 10 f/s forward) which they already had to begin with and wouldn't have had, had they not bombed off the drop, but it kinda feels like you actually carried some of your downward speed. Plus the whole thing just happens faster and with more adrenaline so you don't notice the impact as much because so much more is going on.

    And whoever the chump was the disagreed and said that a bullet shot from a level gun will not hit the ground the same time as one dropped from the same height by hand because the bullet is temporarily in orbit or something, they need to get there facts straight before they confuse more people.

    A fast bullet from a gun might leave the barrel at 1000 ft/sec. Assuming no wind resistance (which is a HUGE factor in this) and a gun height of 5 feet, after one second your bullet will have travelled 1000 feet but dropped 15 feet because of gravity. In order for the bullet to be in orbit the earth would have to curve 20 feet down (15ft dropped plus 5ft to keep the original height) over 1000 feet. I don't know what the curve of the earth is but in 1000 feet it probably curves about a millimeter.

    It is true that a bullet shot from a level gun will hit the ground the same time as one dropped by hand but in reality it is very difficult to duplicate because if you aim even 1% upwards it'll be climbing very fast and vice versa if you aim 1 degree down so it has a huge impact. Plus you'd need a massive perfectly flat surface so your bullet didn't hit anything.
    Last edited by dandurston; 09-16-2005 at 11:50 AM.

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    Nice.

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    -again-
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    Quote Originally Posted by dandurston
    blablalbla.
    Nevermind the physics stuff.... Go and ride your bike, go off a 1 foot to flat as slow as you can, then again as fast as you can....
    Tell me what is smoother..
    sure, falling rate is the same... but it sure doesnt feel like it
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    Quote Originally Posted by [email protected]
    Nevermind the physics stuff.... Go and ride your bike, go off a 1 foot to flat as slow as you can, then again as fast as you can....
    Tell me what is smoother..
    sure, falling rate is the same... but it sure doesnt feel like it

    Beautifully said.

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    Who needs physics?











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    Quote Originally Posted by [email protected]
    Nevermind the physics stuff.... Go and ride your bike, go off a 1 foot to flat as slow as you can, then again as fast as you can....
    Tell me what is smoother..
    sure, falling rate is the same... but it sure doesnt feel like it
    Sure it's smoother at speed but only because it's easier to do. When you go off the drop with speed your front end is suspended for way less time so you need to do way less to land properly. A small weight shift does the trick where as if you creep of the lip you need to be perfectly balanced on the rear wheel for a while in order to land properly.

    If you got the skills they'll both be the same.

  71. #71
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    Quote Originally Posted by Huck Banzai
    drops top flat on a fully, ESPECIALLY a long travel/DH/FR Bike, are REALLY stupid and REALLY bad for equipment...if you try to go to the back wheel A La HT - you load up the suspension/linkages in a way they are absolutely not meant to be loaded making the move hard and REALLY bad for your bike
    Is this really true the F/S bikes shouldn't be 'wheelie dropped' so you land almost right on the balance point and slowly let your front end down??? Seems hard to believe...

  72. #72
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    Quote Originally Posted by dandurston
    Wow, I've lost a lot of respect for a lot of members of this forum. I can't believe how many people out there believe that hitting a drop to flat with speed is somehow less of an impact then if you just slowly wheelie off. This is such basic physics.

    Here's the real deal:

    The milli-second you leave the lip of the drop your bike starts accelerating down at roughly 30 feet per second (9.8 meters per second exactly). Assuming a level drop (no lip) you are would be moving downwards at zero feet per second and after one second of dropping you would be falling 30 feet per second. You average speed is halfway between these two numbers as your acceleration is basically linear. So for that 1 second you averaged 15 feet/second thus you dropped 15 feet roughly. On huge drops wind resistance matters but not much any anything 99% of people ride.


    And whoever the chump was the disagreed and said that a bullet shot from a level gun will not hit the ground the same time as one dropped from the same height by hand because the bullet is temporarily in orbit or something, they need to get there facts straight before they confuse more people.



    It is true that a bullet shot from a level gun will hit the ground the same time as one dropped by hand but in reality it is very difficult to duplicate because if you aim even 1% upwards it'll be climbing very fast and vice versa if you aim 1 degree down so it has a huge impact. Plus you'd need a massive perfectly flat surface so your bullet didn't hit anything.
    Actually, your logic is messed up: gravity's acceleration is not 9.8meters per second, it is 9.8 meters per second squared (9.8meters/s^2).

    As far as the gun goes, explain to me how a normal bullet, fired from a gun, will always hit the ground at the same time that one that is dropped from the same height does. What if you fired the same weight/caliber bullet again, but it was "hot loaded" this time, so it had more force behind it. Wouldn't the bullet travel farther, thus taking longer to impact the ground? Anyone who shoots guns knows that all guns shoot with varying trajectories, however, bullets that weigh very different, when dropped simultaneously from the same height, fall and impact at the same rate. Your physics are jacked up.

    You need to incorporate vectors into your explanation. As far as the drop to flat on a bike, if you hit a 20 foot drop to flat, will it feel the same as a 20 foot drop to 45 degree tranny, going off the drop with identical speeds? Hell no. Why? Because on a drop with a tranny, your impact is absorbed across the ground, and not directly into it- your force vector is impacting the ground at an angle, whereas landing a flat drop would cause that your energy from falling would be absorbed perpendicularly into the ground. Your vector would be more or less straight into the flat ground below. So, that being said, if you hit a 20 foot drop with a lot of speed (and I mean A LOT of speed), you would no longer be hitting the ground at perpendicular, it would be at an angle, which would lessen the force.However, once you hit a 20 foot drop to flat, even with tons of speed, it would be more like hitting a 40 foot drop to tranny because of the added distance you are traveling before impacting the ground. Because of this, I would not advise anyone to huck a 20 foot to flat, unless you are happy about hitting a 30 or 40 foot drop to tranny.
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  73. #73
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    Quote Originally Posted by dandurston
    Is this really true the F/S bikes shouldn't be 'wheelie dropped' so you land almost right on the balance point and slowly let your front end down??? Seems hard to believe...
    you can do it, but its hard to get up there cuz of the suspension bobling, and when u land it bobbles and slams ur front down and on a ht it doesnt and u can balence on ur rear wheel and then slowly set it down. You can do it, but it takes practice, pain, and parts.
    Quote Originally Posted by Tarekith
    Isn't the proper etiquette on this forum to wait until he posts a picture of himself dropping it, and then spend 70 posts arguing about how big it is? I mean, let's not jump the gun, without a pic of his bike in the air, we can't have photoshopped triagulations and geometrical equations showing why it's really 2 feet and not 22 feet.
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    Quote Originally Posted by KennyO
    Actually, you would no longer be hitting the ground at perpendicular, it would be at an angle, which would lessen the force.
    Exactly what I mean but couldnt really explain, thank you
    the bullet thing cant be true... doesnt fit right
    Jake
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    Didn't you read the sticker on that shock? It said not to do whatever you did.

  75. #75
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    How about, riding off a drop fast will give you more forward momentum, thus making it harder to change your direction. The faster you go, the less of an angle you land it at, the more forward momentum you will keep after landing.

    |
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    -------- vs.
    ....\
    .... \
    ---------- = less loss of forward momentum.

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    Quote Originally Posted by KennyO
    Actually, your logic is messed up: gravity's acceleration is not 9.8meters per second, it is 9.8 meters per second squared (9.8meters/s^2).

    As far as the gun goes, explain to me how a normal bullet, fired from a gun, will always hit the ground at the same time that one that is dropped from the same height does. What if you fired the same weight/caliber bullet again, but it was "hot loaded" this time, so it had more force behind it. Wouldn't the bullet travel farther, thus taking longer to impact the ground? Anyone who shoots guns knows that all guns shoot with varying trajectories, however, bullets that weigh very different, when dropped simultaneously from the same height, fall and impact at the same rate. Your physics are jacked up.

    You need to incorporate vectors into your explanation. As far as the drop to flat on a bike, if you hit a 20 foot drop to flat, will it feel the same as a 20 foot drop to 45 degree tranny, going off the drop with identical speeds? Hell no. Why? Because on a drop with a tranny, your impact is absorbed across the ground, and not directly into it- your force vector is impacting the ground at an angle, whereas landing a flat drop would cause that your energy from falling would be absorbed perpendicularly into the ground. Your vector would be more or less straight into the flat ground below. So, that being said, if you hit a 20 foot drop with a lot of speed (and I mean A LOT of speed), you would no longer be hitting the ground at perpendicular, it would be at an angle, which would lessen the force.However, once you hit a 20 foot drop to flat, even with tons of speed, it would be more like hitting a 40 foot drop to tranny because of the added distance you are traveling before impacting the ground. Because of this, I would not advise anyone to huck a 20 foot to flat, unless you are happy about hitting a 30 or 40 foot drop to tranny.
    What you said about gravity accelating at 9.8m/s2 is true. I did fail to mention that but because my calculations were based on a drop that takes 1 sec my results remain the same as 1^2 = 1.

    About the gun thing. It seems hard to believe but it is entirely true. Think of it this way:

    If you fire a bullet downwards at say a 10 degree slope it'll hit the ground almost instantly but if you fire a bullet with a 10 degree upwards slope it'll take quite a long time to hit the ground. The reason for this that some of the force of the gun powder exploding is being used to propel the bullet either up or down...pretty basic so far. In the real world you never have the gun perfectly level so you are either blasting the bullet up into the sky or slamming it into the ground. BUT if you got lucky and happen to have the gun PERFECTLY level then none of that gun powder would propel the bullet up or down. The bullet would be screaming along perfectly parallel to the ground when it leaves the barrel. Because there would be NO upwards force or downwards force exerted by the powder the ONLY force pulling the bullet up or down would be gravity and gravity always gives you the same acceleration of 9.8m/s^2.

    In the real world you never see this happen because you'd need to be SO close to level for this to come even close to happening. The force exerted by the gun powder is tremendous and if you were even a wee little bit of that is used to propel the bullet up or down then your results would be way off. If you were right on you'd never see it happen because the bullet would still be half a mile away.

    In the real world people naturally aim slightly up so this never really happens. Go ask someone who hunts ask what happens when they use a gun that is sighted in at 100 yards to hunt an animal at 200 yards. You need to aim about a foot high to get right where you were aiming. (and a gun sighted in at 100 yards is roughly aimed about 6" higher then where the barrel is aimed cuz the bullet drops significantly even over 100 yards)


    Now back to the whole biking thing:

    The reason I didn't get into vectors is because 75% of the people on here won't know what they are. I find it kind of frustrating how confusing this whole dropping at speed conversation is but I think I can explain it in just a couple sentances. Here goes my best shot:

    Our boy Jonny leaves the level lip of a drop travelling at 10mph. A couple seconds later our boy lands on the perfectly flat landing. When he lands absolutely none of his downward force is transfered into forward force because the landing is flat. As a result after he lands the drop Jonny is still travelling 10mph down the trail (minus wind resistance etc.)

    Because none of the force is transfered into forward momentum (and you can radar someone to confirm this) all of your downward force is absorbed by the ground. The downwards force you have is equal to a drop where you left the lip at 1mph so the hit is of equal force and thus is just as big of an impact.

    This seems to confusing to some people when you totally seperate the up/down forces from the sideways forces. People think that when you leave the lip with speed you travel downwards at an angle (true) instead of straight down and because angle of incidence equals angle of reflection some of your down force must be converted to forward force.

    This is true except it has one glaring oversight. If you leave the lip at 0.001mph and hit the ground at 10mph you are hitting the ground straight on at 10.001mph. If you leave the lip at 10mph, gravity will accelerate you another 10mph down so your actual vector when you hit the ground will have a 45 degree downwards slope which means the speed you're travelling at will be the hypotenuse of 10mph down and 10mph forward which is roughly 14 mph down. So instead of hitting the ground at just 10mph you are hitting faster at about 14 mph.

    The 'angle of incidence = angle of reflection' is another way to look at it but people oversite the fact that you are actually hitting the ground faster so although some force is transfered forward the amount of force that is absorbed by the impact is equal. Seperating the forward and downward forces is just a simpler way to look at it.

    Now that I think about this whole thing more I actually might be wrong. If you hit the ground going 14mph at a 45 degree slope and you come out of it still going 10mph forward (like I said earlier and I believe to be true) then you would have taken less of an impact than a rider to hits the ground at 10.001mph and comes to almost a dead stop.

    The jury is still out for me but I'll be thinking about it...I am 99% sure I'm right about the bullet thing though.

  77. #77
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    Quote Originally Posted by KevinM[Freerider]
    you can do it, but its hard to get up there cuz of the suspension bobling, and when u land it bobbles and slams ur front down and on a ht it doesnt and u can balence on ur rear wheel and then slowly set it down. You can do it, but it takes practice, pain, and parts.
    By parts do you mean it takes the right components, or just that you're going to break a few parts now and then doing it? Or am I completely off?

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    i am in ohysics right now and

    couldn't help laughing at some of you who obviously never took physics or don't remember it at all. with the gun and bullet questions they will both hit the ground at the same time as gravitys pull on any object it the same no matter what it horizontal velocity is. so going faster off of a drop won't make it easier to land or make you hit the ground any slower you just have the speed that smooths it out as you hit. so using a few equations that i have learned within the last two weeks i figured out mathmatically wether you ride off a 30' drop at 20mph or drop straight down it you would still hit the ground at roughly 35mph. don't know if that clears some things up or if it just confused some of you even more.
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    I've always thought it's just a bit harder to be totally smooth cuz of the changing balance point but it's better to try than to just resign your self to flat landings. Who ever intially wrote that it was hard on your bike seems to think the suspension shouldn't be subjected to forces from behind (like it is when you land on the back wheel). This seems unlikely to me but it'd be nice to know if it's hard on your bike cuz it shouldn't be done or because you'll crash a few times learning it like any move worth learning.

  80. #80
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    [QUOTE=dandurston] The 'angle of incidence = angle of reflection' is another way to look at it but people oversite the fact that you are actually hitting the ground faster so although some force is transfered forward the amount of force that is absorbed by the impact is equal. Seperating the forward and downward forces is just a simpler way to look at it. QUOTE]
    If some force is tranferred forward instead of simply back in the exact opposite direction of the falling object, then how can the straight downward impact have the same force as it would have had if there had been no forward motion at all? To illustrate my point, let's go back to that gun analogy, but let's use the gun differently. Let's say that Johnny gets tired of all this dropping to flats, and decides to go hit a real drop for a change. but before he goes, he pulls out his piece because that's the kind of G he is, and aims directly down at the ground, to fire a round directly, perpendicularly into the concrete. Now, this is a stupid thing to do, as anyone can tell, but hey, Johnny is hitting all of these huge flat drops. How smart can he really be anyway? He's just gonna bust up his ride, and try to get his rear shock warranteed. Now, imagine what that bullet is going to do to the concrete, due to impact (besides what it might do to Johnny as well!) Now, Johnny G fires another round, this time, at a 45 degree angle downward, instead of a 90 degree angle. Now what does the bullet do to the concrete? Now, that bullet probably won't harm Johnny G, but it may hurt someone else. (Johnny G doesn't even care about his ride, why care about innocent bystanders?)

    So, ask yourself what the bullet will do differently in these two cases. What will happen to the bullet? What will happen to the concrete? In each case, how will the path of the bullet be different? Will the bullet travel farther in the second shot, after hitting the ground, than it will in the first shot?

    (No animals were harmed in the making of this simulation.)

    As far as the bullet that is fired, falling to the ground at the same rate as the dropped bullet, think about this:

    First of all, you can pretty much level a gun right on. You can bolt a gun to a table rest, and you can level the muzzle just about perfect. You can also use a boresight. You could even use a lazer boresight. That would be real easy.

    Now think on this for a minute: gravity pulls objects down with a constant force. It does not care how much something weighs. However, when you have a forward-moving object, that object now carries energy, because of its mass, and it carries that energy in a direction, according to its momentum. That bullet that is flying through the air is carrying much more energy, in a forward direction, than the dropped bullet is carrying downward. There are some bullets out there that carry over 2 tons of energy upon impact. They have some real knockdown power. However, the dropped bullet carries only the energy that its downward acceleration due to gravity affords it. Gravity exerts the same force on both bullets, the difference is that the dropped bullet carries no energy until it is released, and the only energy it ever gets is from gravity. However, the bullet fired from the gun has lots of energy, and it is going in a direction perpendicular to what gravity is pulling it in. Therefore, gravity needs to exert more force against that bullet in order to change the direction of the bullet's energy. But gravity doesn't exert more force on the fired bullet than the dropped bullet. Gravity exerts equally on all objects. Therefore, it takes longer for gravity to bring the fired bullet into a downward path that it does to bring the dropped bullet down, because the dropped bullet only had potential energy, not kinetic energy like the fired bullet does. The energy makes the fired bullet resist any change in a direction other than the one it is traveling in.

    So, although you would be okay with lying down and letting a dropped bullet land on your stomach, you probably wouldn't be happy to lie down right where the fired bullet hits the ground. That is, unless you are Johnny G, who seems to enjoy torture such as hitting drops to flat. The gangsta's life is a hard one.
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    everything u said is correct in the real world we live in due to certain factors that come into play such as wind resistance, curvature of the earth, and so on, but technically the bullet thing only makes sense in a vacuum. But fortunatel or unfortunately we dont live in a vacuum so we have to account for these factors. As for Johny G, he can go ahead and keep gnarling to flat
    im all about midget drops

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    Kenny,
    I see what you mean with the bike drop thing when you say the bullet that was shot at a 45 degree angle doesn't stop dead like one shot straight down will but rather might bounce and keep going forward. Here's the thing you're missing: The bullet that is shot at 45 degrees isn't shot at the ground as hard as the one that is shot straight down whereas with a bike they both have the exact same downward pull cuz they both spend equal amounts of time in the air being pulled down by gravity.

    If the bullet speed is 1000mph then you can think of it as going forwards at 700mph and downwards at 700mph because the 1000mph is just the hypotenuse of that (700^2 + 700^2 = 1000^2) where as the bullet that is shot straight down is just going 1000mph at the ground. Of course the bullet that is going 700mph forward and 700mph down is way more likely to bounce forward because it's hitting the ground significantly less hard plus it 700mph worth of momentum pulling it forward PLUS the surface tension of the asphalt has a much better chance of reflecting the bullet. To really be fair you'd have to ask: "Why bullet smacks the ground harder: One shot at 1000mph straight down OR one shot at about 1500mph at a 45 degree angle". The answer to which I believe is that the impact is equal except in the case of the 1500mph shot you'll come out of it with some forward speed.

    What you said about the bullet fired from a gun thing about moment, energy etc. is a non-factor. This is because gravity is not trying to slow down or resist the speed that the bullet already has. It isn't fighting the bullets energy but rather it's adding to it. Rather gravity is just adding to the speed of the bullet because instead of going 1000mph level it's going 1003mph down 1 degree.

    If momentum and kinetic energy somehow were able to resist gravity then all man would have had to do to make an airplane would be to get a car going really fast and then hit a pothole to propel it 1 inch into the air and there it would stay until it slowed down or ran into a hill. Why do you think airplanes need wings to fly? The new Bombardier jet I was on last week was crusing at 500mph which = roughly 800,000 yards per hour = 2400000 feet per hour = 600 feet per second which is the speed of an average bullet. I garentee you that if the main wings fell of that plane we couldn't continue cruising along at 30,000 feet (assuming you could fly straight/level etc). Imagine if you rode your bike off a drop super fast. Do you think you'd slowly float to the ground? Nothing is pulling you up and gravity is pulling you down so the downward speed is simply how much time gravity has spent pulling on it.

    Of course I'd be okay if a bullet was dropped on me from 5 feet up but not if I was lying where the bullet that was shot lands but only because the bullet that was fired still has a ton of forward speed when it hits the ground so it would tear a trench down me.
    Last edited by dandurston; 09-28-2005 at 07:39 PM.

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    Hmm... for those of you who are really into this disussion, I'm not going to discuss this in-depth, at least not off the bat. No toes to trample here...

    1. Consider momentum. More importantly, the change of momentum.
    2. Elasticity
    3. Rotation of wheels, considering its air volume, and distribution of impact on ground.
    4. As far as the bullet goes, did everyone remember that the bullet not only has translational momentum, but also rotational momentum? This affects wind resistance a lot, along with the way the bullet falls. Heck, as bikes, how the heck do you think you stay up w/ out falling down?

    Most physics taught in school even college physics is "IDEAL." Go deeper and you shall find the answer you look for.

    Take this into consideration and think about it. You are all right in your respect of the conditions you specify. I just think that the conditions are all in the specs... Just not 100%. Look this stuff up and I'm sure it'll tweak your thoughts a bit.


    -Peace

  84. #84
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    2r x d(4.5x 3.147) = mass - density(breast and butt)

    or something very close
    the trick is ENJOYING YOUR LIFE EACH DAY, don't waste them away wishing for better days

  85. #85
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    i do 6 footers to flat on my GIANT WARP everyday and its still like new...well, after i replaced the BB
    Quote Originally Posted by mothahucker
    Go hit some more two foot plywood jumps in your culdesack on your toys'r'us magma

  86. #86
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    Quote Originally Posted by dandurston
    Kenny,
    I see what you mean with the bike drop thing when you say the bullet that was shot at a 45 degree angle doesn't stop dead like one shot straight down will but rather might bounce and keep going forward. Here's the thing you're missing: The bullet that is shot at 45 degrees isn't shot at the ground as hard as the one that is shot straight down whereas with a bike they both have the exact same downward pull cuz they both spend equal amounts of time in the air being pulled down by gravity.
    "Isn't shot at the ground as hard?" You mean kind of like a bike either going off of a drop at near stand-still, as opposed to one going off a drop at high speed? the difference is how some of the energy is absorbed, and how the rest of it is re-directed. The bullets coming out of the muzzle of the gun have the same muzzle velocity. This muzzle velocity gives the bullets kinetic energy. That energy can either be directed straight into the ground, which will absorb some of the bullet's energy, then redirect the excess energy, which may be carried in the form of fragments of bullet/concrete, or the bullet can be fired incidentally at the concrete, which will redirect the bullet, with the bullet retaining more of its energy instead of the concrete absorbing so much of it.

    Quote Originally Posted by dandurston
    To really be fair you'd have to ask: "Why bullet smacks the ground harder: One shot at 1000mph straight down OR one shot at about 1500mph at a 45 degree angle". The answer to which I believe is that the impact is equal except in the case of the 1500mph shot you'll come out of it with some forward speed..
    Isn't this the real question here anyway? "Why biker smacks the ground harder: coming off a drop and going straight down, OR one coming off at an angle?" Which I in fact stated weeks ago in this thread, that hitting a flat drop at speed will feel like you hit a taller drop with a decent tranny.

    Quote Originally Posted by dandurston
    What you said about the bullet fired from a gun thing about moment, energy etc. is a non-factor. This is because gravity is not trying to slow down or resist the speed that the bullet already has. It isn't fighting the bullets energy but rather it's adding to it. Rather gravity is just adding to the speed of the bullet because instead of going 1000mph level it's going 1003mph down 1 degree. .
    Gravity isn't fighting anything, it just has what it has: the pull of the earth. That doesn't mean that the forward energy of the bullet is just happy to go wherever gravity is going. The energy of the bullet tends to go in the direction it is going.

    Quote Originally Posted by dandurston
    If momentum and kinetic energy somehow were able to resist gravity then all man would have had to do to make an airplane would be to get a car going really fast and then hit a pothole to propel it 1 inch into the air and there it would stay until it slowed down or ran into a hill. Why do you think airplanes need wings to fly? The new Bombardier jet I was on last week was crusing at 500mph which = roughly 800,000 yards per hour = 2400000 feet per hour = 600 feet per second which is the speed of an average bullet. I garentee you that if the main wings fell of that plane we couldn't continue cruising along at 30,000 feet (assuming you could fly straight/level etc). Imagine if you rode your bike off a drop super fast. Do you think you'd slowly float to the ground? Nothing is pulling you up and gravity is pulling you down so the downward speed is simply how much time gravity has spent pulling on it...
    You are pulling what I said out of context. You are telling me that I am saying that gravity doesn't exist to the fired bullet, or that it has no effect. I said no such thing. If a car was going fast, then hit a pothole which propelled it 1 inch into the air, gravity would pull it down. The question of the forward energy of the car and how long it would take for it to come back to the ground just brings us back to the bullets, so I see no point in bringing up a car and a pothole to begin with. I never said gravity had no effect on the forward moving object, but you are saying that the energy in forward motion has no effect on the body that carries it. If the wings fell off of the plane, then it would be just like the bullet, wouldn't it? We would simply be back to the question of the bullet, except it would be a bullet with people riding in it. I think I'm capable of understanding that a plane remains aloft because of wings, and not just because of forward energy.

    As far as bullets go, your .223 cal round does 3000ft/sec. Most bullets zip along quite a bit faster than that plane you were on, unless you specifically use subsonic pistol ammo, like if you were running a silencer, and you didn't want a "sonic boom" coming from your bullet breaking the sound barrier.

    Think about a pendulum swinging. When you let go of the pendulum from one side, why doesn't gravity just pull the pendulum down and hold it there? Why does the pendulum continue to swing back and forth, in continuingly diminishing arcs, until gravity FINALLY overcomes the pendulum's energy? Gravity can't do it all at once, there is too much kinetic energy. Now don't start saying that I said the pendulum will never stop swinging, and don't start saying I said the airplane or the car or the pothole lid or whatever just kept sailing into the sunset. I know gravity is there, what freerider doesn't? Now, if something (like a bullet) were shot from a very high altitude, gravity would continue to act on it, pulling it down, until the bullet was heading straight for the ground. All of the forward energy of the bullet would be depleted by then. The impact of the bullet would be straight into the ground, all of the energy would be absorbed by the ground, the bullet, and whatever energy was still left would be redirected away from the impact. However, if the bullet hit the ground before all forward momentum was lost (like a bike hitting a drop with speed) then less of the energy would need to be absorbed by the ground. More of the energy would stay with the bullet as it continued in forward motion.


    Quote Originally Posted by dandurston
    Of course I'd be okay if a bullet was dropped on me from 5 feet up but not if I was lying where the bullet that was shot lands but only because the bullet that was fired still has a ton of forward speed when it hits the ground so it would tear a trench down me.
    Yeah, but it isn't the speed of the bullet, it is the energy it is carrying that does the damage. That's why a tennis ball hitting you at 100 mph will hurt but not kill, whereas a 4 ton pickup truck going 50 will. That's why you don't hunt deer with .22 rifles. Or tennis balls. Or pickup trucks. Oh wait, I'm in Utah...
    This election is like a turd in a bag on your porch... whether its a blue bag or a red bag, it's still a turd on your porch.

  87. #87
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    Vertical speed is independant of the horizontal speed in scenario like the bullet myth and with dropping to flats. You can read all about why I'm right at a ton of websites of you just type in bullet myths into google. Here's a sample link for you:

    http://www.chuckhawks.com/bullet_trajectory.htm
    http://www.straightdope.com/classics/a5_201a.html <- this was posted in this thread a week ago and should have eliminated this discussion.

    Stuff like kinetic energy, momentum etc are all non-issues. The bottom line is that nothing is holding the bullet up in the air...sure it's moving forward fast but nothing is pulling it up and resisting gravity from pulling it down. If you shot the bullet from a low height ie 1 foot it would hit the ground at the same time as a bullet that is dropped from the same height at the same time but if you were to shot/drop the bullets from say 20 feet up there would actually be a slight difference but only because the curvature of the earth would make the distance the shot bullet has to drop farther even though it would be falling at exactly the same rate. The earth actually curves down 3 feet down every mile. Because the bullet that is shot from 20 feet up has a longer distance to fall it actually hits the ground harder as it had more time for gravity to accelerate it. Regardless there is nothing to keep it from acclerating downwards at 9.8m/s^2

    Our whole basic bike question works on the same principals. There is a vertical and horizontal component to every vector and the vertical component would be equal in both cases as both bikes spend the same amount of time being pulled down by gravity just we learned on those bullet sites. When the bike that dropped off with speed hits all of it's vertical component is lost and only the horizontal component remains and since the vertical components are both equal the impacts are also equal. Drops with speed only feel smoother cuz they are easier to do.
    Last edited by dandurston; 09-29-2005 at 06:27 PM.

  88. #88
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    Quote Originally Posted by dandurston
    Vertical speed is independant of the horizontal speed in scenario like the bullet myth and with dropping to flats. You can read all about why I'm right at a ton of websites of you just type in bullet myths into google. Here's a sample link for you:

    http://www.chuckhawks.com/bullet_trajectory.htm
    http://www.straightdope.com/classics/a5_201a.html <- this was posted in this thread a week ago and should have eliminated this discussion.

    Stuff like kinetic energy, momentum etc are all non-issues. The bottom line is that nothing is holding the bullet up in the air...sure it's moving forward fast but nothing is pulling it up and resisting gravity from pulling it down. If you shot the bullet from a low height ie 1 foot it would hit the ground at the same time as a bullet that is dropped from the same height at the same time but if you were to shot/drop the bullets from say 20 feet up there would actually be a slight difference but only because the curvature of the earth would make the distance the shot bullet has to drop farther even though it would be falling at exactly the same rate. The earth actually curves down 3 feet down every mile. Because the bullet that is shot from 20 feet up has a longer distance to fall it actually hits the ground harder as it had more time for gravity to accelerate it. Regardless there is nothing to keep it from acclerating downwards at 9.8m/s^2

    Our whole basic bike question works on the same principals. There is a vertical and horizontal component to every vector and the vertical component would be equal in both cases as both bikes spend the same amount of time being pulled down by gravity just we learned on those bullet sites. When the bike that dropped off with speed hits all of it's vertical component is lost and only the horizontal component remains and since the vertical components are both equal the impacts are also equal. Drops with speed only feel smoother cuz they are easier to do.
    If we simply wanted to use "Straight Dope", you would be wrong anyway (as far as the bullet thing goes), but that is only due to the "earth curvature" idea. You're not talking a big time difference there, but there is a difference. You're not talking a great amount of time difference between the fired round and the dropped round either, but you are still discounting the forward energy.

    You keep implying that I am saying that something is holding the bullet up in the air. Why do I have to keep telling you that I'm not saying that? I am not saying that some non-existent force is holding the bullet aloft, I am saying that a very existent energy is present in the bullet's forward path. Quoting from your other site:

    "High Velocity Bullets. Bullets at 2600 fps and up, such as the .223, 22-250, .243/6mm, .270, .308, 30-06, follow a much lower arc to reach a target, and their useful range can be upward of 200 yards. These are often referred to as "flatter" trajectories. With higher velocities, these bullets go much further before gravity and air resistance cause them to fall below the initial line of sight."

    You still haven't explained the "pendulum model" that I brought up. If gravity has no concern for forward momentum, then why does the pendulum continue to swing forward and up against the force of gravity? Is there some force "holding it up"? No. It has the same thing the bullet has: energy.

    You keep talking about the component vectors of riding off of a drop to flat, but your use of the horizontal and vertical vectors work only if you rode off of a drop with speed, stopped in mid-air, then fell straight down. You are not taking into account the forward motion. This is why I brought up the idea of shooting the bullet into the ground. Why will one do more damage to both the bullet and the ground more than the other, even though the bullets are identical in mass and energy? Why will one bullet slam straight into the ground, losing all of its energy, whereas the other will hit the ground, momentarily slide across the ground, then ricochet away, still carrying a lot of its energy? What does energy have to do with the bullet? The energy determines how hard the bullet hits. If the bullet loses all of that energy at once, in one place, then it hits hard. If the bullet loses the energy across a distance, it is a softer hit. If a bike comes off of a drop, and heads directly to the ground, all energy is lost at once. However, if the bike hits the ground at an angle, all energy is not lost all at once, thus the impact is not as severe. Why do you think that a tranny landing is so much better to land in, even if you have almost no forward momentum at all? Even though gravity is pulling the bike down, all of the energy the bike has in its path of travel is not immediately absorbed; rather, it is absorbed across a distance, over time.
    This election is like a turd in a bag on your porch... whether its a blue bag or a red bag, it's still a turd on your porch.

  89. #89
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    All I'm saying is that forward energy/momentum has no effect on how hard something hits the ground or how fast it falls. With the pendulum thing all that's happening is that gravity is pulling it down but then because it's on a rotational axis that gravity produced speed is transfered into horizontal speed just like hitting a drop to a nice transition. Gravity gives you the downward speed and then the transition absorbs some of it and some of it it reflects forward. A pendulum is a much smoother transition than a bike landing so almost none of the energy is lost so the pendulum keeps swinging up but the ever present and always equal gravity immediately starts to slow the pendulum down as it tries to climb. Since almost no energy was lost it takes the same amount of distance to stop and pendulum as it did to accelerate it so it comes to a stop. Here's a nice way to prove that it's all gravity: Try dropping a ball 1 foot and measure (or calculate) it's speed right before it hits the ground. The get a pendulum with an equal amount of vertical drop and measure it's speed at the bottom of its path. You'll notice both objects have the exact same gross speed after they've falling 1 foot even though the pendulum had to travel farther to get there as it was forced to take a longer path by it's axis. The only difference is that the pendulum might be going 2m/s sideways instead of 2 m/s down like the ball will be. If you roll a ball down a 45 degree slope (assuming no friction) it's speed when it reaches the ground will be exactly that of a ball dropped straight down from the same height.

    I really don't know how to explain to you the forward energy has no effect on how fast something gets pulled down. You quote the following from the first link I posted:

    "With higher velocities, these bullets go much further before gravity and air resistance cause them to fall below the initial line of sight"

    I don't think you understand what's really going on here. He's not saying that these fast bullet go for a while before gravity really takes over. A bullets sights are not lined up parallel to the barrel but rather they look down slightly so that when you aim them level the barrel is actually aimed up a little bit. Because the barrel is aimed up but the sights are looking level the bullet will rise above your sight line when shot but gravity is always there pulling down and soon the bullet drops below that sight line again. All he's saying is that faster bullets travel farther before this happens because they are shot upwards harder so gravity has more work to do. The fast velocity doesn't stop the gravity from fully doing it's work it just gives gravity a bigger job because you're shooting the bullet higher up into the air so it has farther to fall before it crosses the sight line.

    Later is your post you say the following:
    "your use of the horizontal and vertical vectors work only if you rode off of a drop with speed, stopped in mid-air, then fell straight down. You are not taking into account the forward motion."

    I'm not sure what physics you've learned but this statement is wrong. What I'm saying is when you are travelling downwards at an angle you can think of your bike as moving forward at a certain speed and downwards at a certain speed and seperating the bikes motion into these two components is a simpler way of looking at it. If you do any calculations you'll notice the answers some out identical. The bottom line is that when you ride your bike off the drop at speed you drop downwards at an angle but you are still approaching the ground at a certain rate of speed just like you might be approaching the tree in front of you at a certain rate. The rate of speed at which you are approaching the ground as totally absorbed when you hit and just the forward component remains. Because the downward component is perfectly equal to the downward component of a bike that just slowly tipped off the drop the impacts will be equal.

    The components are equal, both components are fully absorbed over the same amount of time therefore the deceleration rates are the same therefore the impact is the same.

    I suggest you go talk to a physics teacher or someone else because perhaps they can explain this more clearly to you. All forward motion does is mask what is really going on with the downward components which are equal in every way.

  90. #90
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    Look at this drawing I made..... Teh closer to 180 degrees the smoother the drop will be.. PERIOD..... nuff said..
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    Didn't you read the sticker on that shock? It said not to do whatever you did.

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    Not true! Why? Because although you hit at a shallow angle when you've got speed you're also hitting the ground harder. If the drop is 16 feet than you'll have exactly one second of hang time which means you'll be dropping downwards at 32 feet per second right before you hit. If you just go off slow that's the speed you hit the ground with. If you go off with speed you hit the ground faster cuz you're going 33 feet per second (yeah its fast but it makes the math easier) forward plus you'll gain 33feet per second down since your hang time is the same so right before you hit you'll actually be moving at 33feet/sec forward and 33 feet/sec down which gives you a resultant speed of about 43feet per second down at 45 degrees.

    IF you hit the ground at an angle like in pic 2 at the SAME speed as you hit the ground in pic 1 then obviously pic 2 will be smoother but simple physics reveals that your total speed in pic 2 is actual significantly higher so you are flying at the ground faster. Fortunately you also come in a shallower angle so it cancels each other out and the hit is the same.

    Basic rule of physics: The faster you leave the drop the shallower of an angle you'll land at (good) but you'll hit the ground proportionally faster too so the actual force of the impact is the same.

    Your pictures reveal that a fast drop to flat will be less of an impact than a slower drop to a nice tranny (145 degrees vs 135). You can't just look at the angle you come in at. You need to look at your total speed at the time of impact and the slow drops have less so it all works out even.

  92. #92
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    Opinion of a High School Senior

    Quote Originally Posted by [email protected]
    Look at this drawing I made..... Teh closer to 180 degrees the smoother the drop will be.. PERIOD..... nuff said..
    I am only a high school senior, but these are my thoughts on the topic. The reason a sloped landing feels so smooth is because your downward motion is converted into forward motion as you hit the slope. Now, onto a flat landing. Flat is flat, and no matter how fast you take it, the ground is still flat. Since the landing is flat, your downward motion cant be converted into forward motion. It is all absorbed into your suspension, tires, and into your as well. As your suspension and tires reboud, they release that absorbed energy. Over and out
    If I want your opinion, I will give give it to you...

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  93. #93
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    Quote Originally Posted by Lickqid
    So a 6 ft drop off my roof straight into the back yard be a foolish thing to do on a Gemini 900 w/ Dorado fork?
    ive got a gemini+sherman and i did a 5.5 to flat, if its at your house throw together a plywood tranny.
    I HATE WORK, WORK IS BAD, WORK = NO BIKE, NO BIKE = NO GOOD

  94. #94
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    Quote Originally Posted by puttsey
    i do 6 footers to flat on my GIANT WARP everyday and its still like new...well, after i replaced the BB

    you poor poor poor poor person. I HATE WARPS!!!!!
    I HATE WORK, WORK IS BAD, WORK = NO BIKE, NO BIKE = NO GOOD

  95. #95
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    Quote Originally Posted by Mountainbikextremist
    I am only a high school senior, but these are my thoughts on the topic. The reason a sloped landing feels so smooth is because your downward motion is converted into forward motion as you hit the slope. Now, onto a flat landing. Flat is flat, and no matter how fast you take it, the ground is still flat. Since the landing is flat, your downward motion cant be converted into forward motion. It is all absorbed into your suspension, tires, and into your as well. As your suspension and tires reboud, they release that absorbed energy. Over and out
    Exactly! You spend the same amount of time in the air whether or not your flew off with speed which means gravity spends the same amount of time accelerating you downwards and yeah 'flat is flat', none of this downward speed is converted to forward speed so the hit is identical.

    Drops with speed are generally smoother but only because they're easier to do.

    Drops with speed are actually a slightly bigger hit because the curvature of the earth makes you drop about one 100th of millimeter farther when you huck off fast...

  96. #96
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    Seems like a number of you need to retake physics...or just shut the hell up. Your forward speed going off a drop-to-flat is quite independent from your vertical speed when you hit the ground. If you were to drop 6' to flat with a rigid bike it would be just like jumping from that height and landing on your feet. While it is generally accepted that it is possible to do this without hurting yourself, those that have done it, or those who have jumped from higher, should know that it isn't exactly pleasant. Acceleration of earths gravity is approximately 10m per second per second.

    Moral of the story...

    BUILD A TRANNY!!!

  97. #97
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    Quote Originally Posted by KennyO

    What does it all boil down to? Two things:

    1. don't worry about having to wear an oxygen mask to go to the bank in the future.
    2. drops to flat are ghetto.
    3. dwarves riding big bikes is a bizzare thing.
    That's 3 things. All teh funny though...


    dorps to fart is teh suck.

  98. #98
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    Quote Originally Posted by hardcore newbie
    you poor poor poor poor person. I HATE WARPS!!!!!
    I love mine, its super strong and sexy....but im getting an 06 stinky right when they come out, a gift from my dad when he gets a job..hahhaha........any things i should know about the stinkys??
    Quote Originally Posted by mothahucker
    Go hit some more two foot plywood jumps in your culdesack on your toys'r'us magma

  99. #99
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    Quote Originally Posted by puttsey
    I love mine, its super strong and sexy....but im getting an 06 stinky right when they come out, a gift from my dad when he gets a job..hahhaha........any things i should know about the stinkys??
    the 2006 look friggin awesomez
    I HATE WORK, WORK IS BAD, WORK = NO BIKE, NO BIKE = NO GOOD

  100. #100
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    X and Y coordinates are not related to eatchother in anyway, unless you are speaking of orbit.....If anyone even took pre-calc you learned this in Vectors. as for the gun thing. If shot horizontally and another bullet dropped they will both hit the ground at the same time. Because the only thing effecting the Y-Axis is gravity, and it pulls the same amount on objects no matter what their velocity...(even on oribiting masses where they have such a velocity that when they orbit a sphere. i.e. earth they are going in a straight enough path to counter the amount dropped due to gravity)

    it just feels smoother.

  101. #101
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    good man! nice summary. Here's a better one... BUILD A TRANNY!

  102. #102
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    Quote Originally Posted by Mountainbikextremist
    I am only a high school senior, but these are my thoughts on the topic. The reason a sloped landing feels so smooth is because your downward motion is converted into forward motion as you hit the slope. Now, onto a flat landing. Flat is flat, and no matter how fast you take it, the ground is still flat. Since the landing is flat, your downward motion cant be converted into forward motion. It is all absorbed into your suspension, tires, and into your as well. As your suspension and tires reboud, they release that absorbed energy. Over and out
    I'm only a senior in high school as well, but its got my vote.

  103. #103
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    Quote Originally Posted by Lickqid
    I'm only a senior in high school as well, but its got my vote.
    But when you drop to a flat landing your going down, your still going forward, atleast I am, and I think thats what most people think about when they drescribe something this way. I don't thin most of us are doing a trials style drop straight down. If you make your approach at speed then drop, or bunny hop to clear any lip, you are traveling downward, but your also going forward right.

  104. #104
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    I respectfully accept.

    Quote Originally Posted by dandurston
    Not true! Why? Because although you hit at a shallow angle when you've got speed you're also hitting the ground harder. If the drop is 16 feet than you'll have exactly one second of hang time which means you'll be dropping downwards at 32 feet per second right before you hit. If you just go off slow that's the speed you hit the ground with. If you go off with speed you hit the ground faster cuz you're going 33 feet per second (yeah its fast but it makes the math easier) forward plus you'll gain 33feet per second down since your hang time is the same so right before you hit you'll actually be moving at 33feet/sec forward and 33 feet/sec down which gives you a resultant speed of about 43feet per second down at 45 degrees.

    IF you hit the ground at an angle like in pic 2 at the SAME speed as you hit the ground in pic 1 then obviously pic 2 will be smoother but simple physics reveals that your total speed in pic 2 is actual significantly higher so you are flying at the ground faster. Fortunately you also come in a shallower angle so it cancels each other out and the hit is the same.

    Basic rule of physics: The faster you leave the drop the shallower of an angle you'll land at (good) but you'll hit the ground proportionally faster too so the actual force of the impact is the same.

    Your pictures reveal that a fast drop to flat will be less of an impact than a slower drop to a nice tranny (145 degrees vs 135). You can't just look at the angle you come in at. You need to look at your total speed at the time of impact and the slow drops have less so it all works out even.
    You convinced me, I can't think of anything else. From here forward, I give the bird to any flat drop, fast or slow. No disrespect to the trials guys.
    This election is like a turd in a bag on your porch... whether its a blue bag or a red bag, it's still a turd on your porch.

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    Last Post: 05-22-2004, 09:47 AM

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