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Is a Flat Landing Really That Bad?

PB Forum :: Freeride & Slopestyle
Is a Flat Landing Really That Bad?
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flag potvinwannab
Posted: Oct 10, 2007 at 19:18 Quote
bigquoteshey umm if moutain bikes are supposedly not as strong as a bmx bike as far a materials and geometry then how come you would pay like 2000 more dollars for a mountain bike that has 8 inches of suspension and not ride it hard because you afraid of breaking it, just go by a 500 dollar bmx bike and ride the hell out of it

Its not that mountain bikes arent as strong as bmx bikes, if anything they are stronger (material wise) but the way the two are built is very different. BMX have almost vertical headtubes which directs forces vertically through the chromoly fork, and it can easily take the hit without braking, or putting too much leverage on the headtube. A mountain bike with a 200 mm fork puts the headtube of most bikes somewhere in the 64 degree angle range. The same drop you do on a bmx puts an exponential amount more of force on a dh frame. If you put even a 100 mm suspension fork on a bmx and try doing a 10 foot drop to flat you will most likely damage your frame. That being said, front triangles dont break very often, drop outs and chain stays are what tend to crack, and that comes down to the frame just being longer and the different leverage amounts. Also you will find doing a dh race on a dh bike alot more "fun" to say the least if you use the appropriate bike.
flag cosmothepirate
Posted: Oct 10, 2007 at 22:15 Quote
potvinwannab wrote:
bigquoteshey umm if moutain bikes are supposedly not as strong as a bmx bike as far a materials and geometry then how come you would pay like 2000 more dollars for a mountain bike that has 8 inches of suspension and not ride it hard because you afraid of breaking it, just go by a 500 dollar bmx bike and ride the hell out of it

Its not that mountain bikes arent as strong as bmx bikes, if anything they are stronger (material wise) but the way the two are built is very different. BMX have almost vertical headtubes which directs forces vertically through the chromoly fork, and it can easily take the hit without braking, or putting too much leverage on the headtube. A mountain bike with a 200 mm fork puts the headtube of most bikes somewhere in the 64 degree angle range. The same drop you do on a bmx puts an exponential amount more of force on a dh frame. If you put even a 100 mm suspension fork on a bmx and try doing a 10 foot drop to flat you will most likely damage your frame. That being said, front triangles dont break very often, drop outs and chain stays are what tend to crack, and that comes down to the frame just being longer and the different leverage amounts. Also you will find doing a dh race on a dh bike alot more "fun" to say the least if you use the appropriate bike.

HEY EVERYONE THE THREAD IS NOT SERVING ITS PURPOSE ANY MORE SO WE SHUD EITHER GET BACK ON TOPIC OR END THE THREAD
flag gabor
Posted: Oct 11, 2007 at 7:54 Quote
billygoatsgruff wrote:
This planes thing is pissing me off...
A plane needs to move forward fast because the wings generate 'lift' as air passes over them. The faster a plane goes - the more 'lift' the wings generate.

Here's a good link to see how objects behave in freefall:

http://www.physicsclassroom.com/Class/vectors/U3L2a.html
It's something to do with a partial vacuum right? The upper surface of the wing is more curved than the lower surface, the air rushes past the upper surface faster, and the partial vacuum creates a movement of air.
flag dhcyc
Posted: Oct 12, 2007 at 7:39 Quote
you know jumping to flat is not a very pleasant thing and if people ride for the pleasue of riding itself they won't do hardcore like that just because is hardcore, not a pleasure, it's not even cool. skakteboarders do it cuz city is their trail, not many good landings there...oh and they don't have brakes, they have to jump to flat
flag SAVAGE-RIDER
Posted: Oct 12, 2007 at 13:43 Quote
but still if your going relatively fast and you jump off..say a 5 foot table top, it would hurt a bit yeah but if your going fast enough not to drop you'll most likely glide through the air. just like when a plane comes down to land..what does it land on..flat surface.so if we take that analogy and we put it towards bikes if you have the right angle and land properly you should be fine landing flat. yes i know bikes don't weigh 70 tonnes..
flag dhcyc
Posted: Oct 13, 2007 at 0:00 Quote
I think I know what u mean but anyway the speed ur going to have just before the landing will be the same as when u jumped off and had not that long flight, or even did't almost fly forward. But the feeling on flight itself is better than just being dropped from the top to the bottom at low speed, that gives more stability in the moment of the landing. gotta add too that planes have wings that let them land smoothly, we don't, so we gotta count on illusion ;P
flag hampsteadbandit
Posted: Oct 13, 2007 at 6:21 Quote
Its not that mountain bikes arent as strong as bmx bikes, if anything they are stronger (material wise) but the way the two are built is very different.

you are joking right?

modern bmx frames are built from high quality, heat treated cromoly steel which has a huge tensile strength, many times higher than 6000 or 7000 series aluminimum alloy used for mountain bike frames

steel does not suffer stress fatigue from every little knock and bump, which is something that unfortunately happens to aluminium alloy frames that mountain bikes are typically built from...you have to breach the yield strength of steel to cause any damage to the material

in addition, the compact nature of a bmx frame, and the lack of suspension pivots, shock absorber mounts and often conventional frame design (BMX is traditional double triangle like a hardtail mountain bike) means that the BMX frame is extremely strong in both compression, tension and to resist twisting forces

20" wheels are substantially stronger than 26" wheels, especially in side loadings which is where 26" wheels often fail (think taco)

high stressed bmx parts like the fork, cranks and handlebar are again made from the highest quality heat treated cromoly steel so very resistant to bending or fatigue loads

its a different bike designed for a different purpose, and the way a bmx is ridden is very different with the rider's taking the huge drops on street very skilled and able to absorb much of the force with their arms and legs
flag irvinegr
Posted: Oct 13, 2007 at 6:56 Quote
i donno if this was meantioned already in this thread but Trials riders do big drops to flat all the time. and some do huge drops to rails and stuff and some of them ride 26" wheels.
flag shacabahalla
Posted: Oct 13, 2007 at 9:08 Quote
irvinegr wrote:
i donno if this was meantioned already in this thread but Trials riders do big drops to flat all the time. and some do huge drops to rails and stuff and some of them ride 26" wheels.

its fine for them cos if you watch them they land rear wheel first and absorb the energy, its not really a good idea to do that when your moving foward at speed say on a dh track
flag potvinwannab
Posted: Oct 13, 2007 at 9:39 Quote
[Quoten]you are joking right?

modern bmx frames are built from high quality, heat treated cromoly steel which has a huge tensile strength, many times higher than 6000 or 7000 series aluminimum alloy used for mountain bike frames

steel does not suffer stress fatigue from every little knock and bump, which is something that unfortunately happens to aluminium alloy frames that mountain bikes are typically built from...you have to breach the yield strength of steel to cause any damage to the material

in addition, the compact nature of a bmx frame, and the lack of suspension pivots, shock absorber mounts and often conventional frame design (BMX is traditional double triangle like a hardtail mountain bike) means that the BMX frame is extremely strong in both compression, tension and to resist twisting forces

20" wheels are substantially stronger than 26" wheels, especially in side loadings which is where 26" wheels often fail (think taco)

high stressed bmx parts like the fork, cranks and handlebar are again made from the highest quality heat treated cromoly steel so very resistant to bending or fatigue loads

its a different bike designed for a different purpose, and the way a bmx is ridden is very different with the rider's taking the huge drops on street very skilled and able to absorb much of the force with their arms and legs[/Quoten]


No i am aware that chromoly is MUCH stronger than aluminum, but when you take into account mountain bikes have thicker tube walls, headtubes, gusseting, and cnc'd parts the actual heft of the mountain bike is more than the bmx. Basically what im saying is if a bmx were stretched out to the size of a regular mountain bike the mountain bike would be stronger. Also keep in mind i was including ALL mountain bikes in my statement including the ones like brooklyn and canfield that are indeed made out of chromoly. I said material-wise, not design wise. I know that a compact bmx is stronger than mountain bike and design wise a bmx is stronger than a mountain bike. BUT if you made an aluminum bmx bike with an 8mm headtube, monster headtube gussets, cnc'd chainstay yoke and droputs, and the tubing used in typical freeride bikes, it would be just as strong or maybe stronger than a typical bmx, not taking into effect the fatigue life or the typical grinding done in street riding. All the extra material is meant to cope with the extra stress put on welds in a dh frame, to slow the fatigue effect, and spread stress more evenly through the longer mtb frame. Basically both bikes are designes well for what they do best, and if you want the best of both worlds get a chromoly mountain bike frame like a Brooklyn or a 24seven dark angel. I read once with all the reinforcements made to modern aluminum mountain bike frames through the tripling or even quadrupling the tube wall size of regular chromoly tubes, that for a couple of years the aluminum frame is actually just as strong as the chromo one without weighing as much. When purchasing a mountain bike frame it doesnt even matter which material you go with as long as you dont plan to hold on to your frame for more than 4 or 5 years and as long as it has a warranty because its easy to screw up an aluminum weld.
flag ridingqc
Posted: Oct 16, 2007 at 21:45 Quote
bullitxl wrote:
johnthewolf wrote:
hey bullitxl, do you think you could explain why then it does feel smoother to land a drop to flat the more speed you have?

if you read the previous page, you'll see that the current explanations attemps were quite miserable...!

The fact that some people think that it "feels smoother to land a drop to flat the more speed you have" is just that, only a "feel" because on paper, from the same height, there's no difference. It probably only feels that way because they have more forward momentum when they hit it faster.

Neglecting friction, say you leave a drop perfectly horizontal at 20km/h your horizontal velocity is 20km/h when you leave the ledge and when you hit the ground. Now hit the same drop at 40km/h your horizontal velocity is 40km/h when you leave the drop and when you hit the ground. In both cases your vertical velocity is zero at the instant you leave the ledge.

In both cases you fall 5 feet and you would be in the air for 0.56 seconds. Your vertical velocity in both cases when you hit the level ground is 9.81m/s^2/0.56 seconds = 5.47m/s or 19.6 km/h.

Since you fall the same height in both cases, and hit the ground with the same vertical velocity, the vertical force you impact the ground with in both cases is the same.


Look what this guy said is true the ONLY thing that made us think that going faster off a drop is smooter is that our wheels (witch turn faster) absorb the impact on a large area (maybe 1/4 turn) instead of 1 inch when falling with no speed. So when you're going faster your bike is stronger !!
flag hampsteadbandit
Posted: Oct 17, 2007 at 3:49 Quote
the big problem with aluminium alloy as a material is that it fatigues from the first pedal stroke onwards...every knock and bump puts a fatigue load, no matter how many gussets or reinforcements you make to the frame, we have seen the most overbuilt aluminium alloy frames such as the 24 Bicycles Porn King and Le Toy, and Banshee Scream still crack despite the heavy frame weight (very thick tubing) and overbuilt design

...and aluminium has a nasty tendency to suddenly fail (catastrophic failure) whereas steel tends to bend

steel does not fatigue unless the yield strength is breached, that is the key difference between the two materials
flag howiehucker
Posted: Oct 17, 2007 at 4:02 Quote
well mate to be honest with you if people are afraid to flat land (because they cant)they shouldnt be riding
biking isnt about (oh i cant do this oh hat hasnt got a landing)
fuk sake people go out and ride it
i rode trials so maybe thats y im not afraid of flat landing
in fact all the gaps i ride i mess about and aim to clear the landing and flat land it

and ur right buddy that is what are suspension and big tires are for

i no people are going to quote what ive just written but they no im right and there riding like pussys

trust me mate just ride what u can and if u cant try it and u can
flag odin333
Posted: Oct 17, 2007 at 4:08 Quote
new professional skateboard fully complete= $200
new professional mountain bike= $2800
new rims, tires, and crank= $400
new skatebaording trucks and wheels= $120


everythings more expensive so were taking care of it.
flag
Posted: Oct 17, 2007 at 11:00 Quote
howiehucker wrote:
well mate to be honest with you if people are afraid to flat land (because they cant)they shouldnt be riding
biking isnt about (oh i cant do this oh hat hasnt got a landing)
fuk sake people go out and ride it
i rode trials so maybe thats y im not afraid of flat landing
in fact all the gaps i ride i mess about and aim to clear the landing and flat land it

and ur right buddy that is what are suspension and big tires are for

i no people are going to quote what ive just written but they no im right and there riding like pussys

trust me mate just ride what u can and if u cant try it and u can

Its true... its very true i know i was thinking it and im glad someone else said it, its true, alot of people are afraid, i know people who wont clear a small like 8 set of stairs becuase its to flat, if you know how to suck it up you can drop alot of stuff and land alot of flats

 


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