imaginary at arbitrary in Sydney, Australia - photo by angusmurray

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Got bored doing physics study so I decided to spice things up a bit... hope it is useful for everyone!

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179 Comments

+ 203

lodonnell243 (Mar 14, 2009 at 14:29)

A real physicist would take g to be 9.81, therefore your theory is incorrect. Think of the people who have read this and are now going to get hurt... Tut tut Razz

+ 22

g3cko (Mar 16, 2009 at 9:02)

haha - you should write a new formula!! Big Grin

+ 54

timwestwood (Mar 23, 2009 at 15:38)

he has done it in the mechanics form as in maths where it is only 9.8

+ 14

angusmurray (Mar 26, 2009 at 3:36)

yes, you get props for that

+ 20

ali-chapple (Mar 27, 2009 at 10:37)

my god i thort i'd escaped this once i got home. altho wile i'm here, you should include an air friction coefficient in ur answer and the friction coefficient created by the tyres on the dirt. and 9.8 is a rookie mistake Razz

and one more thing just to be annoying. always specify units of angles (degrees or radians) altho i realise it has to be degrees in this case, so i'l let u off Big Grin

lecture over hav a nice day kids!

timwestwood (Mar 27, 2009 at 11:38)

if you was going to do that you would have to include the energy lost with suspention forks ? would you have to use inertia

+ 35

ddex (Mar 29, 2009 at 4:30)

does it work for full suspension bikes ? Wink

+ 15

lodonnell243 (Apr 2, 2009 at 12:01)

lets sue the bastard! as if he has the copyrights for this formula! Wink

spongosauraus (Apr 5, 2009 at 12:38)

this is very very very picky
but you'd could take direction into:

if an object is fired at x ms ^(-1)
and fired north, east south and west
it ill travel further when going west

angusmurray (Apr 6, 2009 at 1:25)

isnt that because of the rotation of the earth?

spongosauraus (Apr 6, 2009 at 3:39)

Yeah

angusmurray (Apr 6, 2009 at 4:20)

niiice

mattrox (Apr 7, 2009 at 17:47)

evry one keeps sayin, take into consideration the rebound and preload of the forks for interia, i dont think that you can get an accurate measure ment of a forks, preload and rebound, just beacue each for is different, and no doubt each run the rider takes may be rougher or smoother then the next jump, so it might be differnt measurements each time. but props dude.

+ 12

Caiokv (Apr 7, 2009 at 17:53)

but the rebound and the preload influence, as do the air resistance, the temperature, the height, the tires pressure, the mass center, rider position (with variates during the jump).....
But in general cool and useles stuff!!!!

mattrox (Apr 7, 2009 at 17:59)

yep, lmao

D-Monster (Apr 9, 2009 at 10:49)

A real physicist would take g to be 9.81, therefore your theory is incorrect. Think of the people who have read this and are now going to get hurt... Tut tut

Re: that would only make cm's of diffence Razz

so he's right

+ 13

D-Monster (Apr 9, 2009 at 10:50)

and Forgot Weight of Rider + Bike and the wind factor

+ 10

angusmurray (Apr 9, 2009 at 18:29)

dude, weight does not affect simple projectile motion; read up on your physics.

and if you want to include wind (which is a force as a function of velocity) it is too hard to integrate nicely
but when you're only going maybe 20 kph it doesnt do a great deal

lodonnell243 (Apr 15, 2009 at 18:27)

D-Monster:
You are not getting the principles right here. It is the PRINCIPLE he has not used 9.81 as a physicist that I am getting at Razz

Doing a physics A-level, I am being picky on the point I would lose marks for that rather than I am being right twat. Wink

radz333 (Apr 19, 2009 at 10:54)

oh dear lol serious mate u have too much time, just do the jump and if you fail, u try again thats my theory lol

+ 18

fr112358 (Apr 21, 2009 at 21:25)

This is so funny. Physicists on PB Salute

+ 14

henrytgreene (Apr 21, 2009 at 21:28)

Everybody shut up. I'm failing geometry and you guys are talking about this stuff like you talk about women. My brain is deteriorating from it all. Plus the best and easiest way to know how fast to go is to just guess it and hit it.

- 23

woodygebhardt (Apr 24, 2009 at 23:15) (Below Threshold) show comment

im passing geometry and im a year ahead of my grade lol

at least im not one of the nerds 2 years ahead in trig/alg2 who might understand this shit lol

+ 11

ziegele (May 6, 2009 at 21:23)

i got lost in the first sentence.......

- 12

dave6797 (May 7, 2009 at 9:43) (Below Threshold) show comment

just worked it out if you are in the air for 1 second you will of traveled 81.9 miles (130.3 km) therefore if you are in the air for 2.5 seconds and the jump is facing west realisticly you will be jumping 204.75 miles (329.5 km) + the length of the jump. think about that one then!!

fooox (May 14, 2009 at 12:36)

Lol, this is what my friend just said who got an offer from cambridge to read Maths: "OMG lol! I had no idea there were so many nerds on pinkbike. I'm pretty sure though that there's an x missing three lines from the bottom (I think it should be v^2sin(theta)cos(theta)x rather than just v^2sin(theta)cos(theta)) and so basically Angus Murray has completely f*cked this up and is going to be the reason that loads of dirtjumpers hurt themselves."

fooox (May 14, 2009 at 14:46)

My other "immensely cool" friend who's got an engineering offer from Cambridge has confirmed the above and also says:
Alichapple: You are wrong it makes no difference if you use degrees or radians
Spongosaurus: You are also categorically wrong: "if an object is fired at x ms ^(-1)
and fired north, east south and west
it will travel further when going west" no, simply no. That doesn't happen.
Angusmurray: "he is impressed with your physics but declares that your formula is messy!"

spongosauraus (May 14, 2009 at 15:05)

well you can tell your friend to shove his diploma up his ass because that is a basic fact and if he doesnt know that then good luck with his diploma

angusmurray (May 14, 2009 at 23:53)

f*ck i forgot to carry the x through

angusmurray (May 14, 2009 at 23:54)

......currently working on a new equation (hopefully less messy)......

angusmurray (May 15, 2009 at 0:24)

actually, just put an x next to the sin(theta)cos(theta) on the bottom of the fraction under the square root

and its all good

im sorry if anyone got hurt

angusmurray (May 15, 2009 at 1:14)

so the official equation is as follows::::::::

v=sqrt((-4.9*L^2)/((y2-y1)*(cos(theta))^2-cos(theta)*sin(theta)*L))

Caiokv (May 15, 2009 at 10:09)

c++ language?

angusmurray (May 16, 2009 at 20:32)

nah its just normal math syntax

like what you would type into maple or whatever you use..

teamn2 (May 24, 2009 at 23:30)

its like chinese to me haha Razz

recklessness (Aug 3, 2009 at 7:26)

All math aside, I just take a few run-ins and hit jumps. No calculations, just balls and a tiny bit of skill. LOL @ your math and the argument that ensued.

ZAKLOVESDJ (Aug 26, 2009 at 11:48)

Speed + Skill = Clear Safely Smile

freedjdh (Sep 15, 2009 at 19:40)

show this to your math teacher for extra credit! haha

DylSay (Sep 16, 2009 at 7:49)

or u just man up and cold turkey hit ANYTHING AND EVERYTHING And stop being such a wuss

brandyn16 (Dec 5, 2009 at 17:05)

to many variables . wind, tricks, how much you boost,rider skill, ect.

ericpalmer (Jul 7, 2010 at 1:23)

just add an approximation variable to the equation to sort it out then. Simple...

cyberhawk Plus (Jul 27, 2010 at 3:16)

i say gddmm

castbreeder (Jul 27, 2010 at 3:31)

9.8, 9,79... or 9.81 not important
en.wikipedia.org/wiki/Gravity_of_Earth

D1rtJumper (Nov 28, 2010 at 22:15)

Guys. Just build it and test it. Who cares about physics.

kiGs13 (Feb 2, 2011 at 14:49)

I try and read this........and then my head starts to hurt.

shockabahala Plus (Feb 2, 2011 at 19:53)

i say you take this peice of paper, fold it up very very carefully... (days, maybe even weeks after) Mail it out to the mo fo that made this, and enclose a letter saying "shove this up your ass you gay homosexual f*ggot! i'm giv'en 'er full steeze!!"

thank you kindly,
Aaron Stacey

Rattsl (Feb 17, 2011 at 23:23)

I can't even read that. Is that a bad thing?

cyberhawk Plus (Feb 18, 2011 at 0:03)

whats on the picture.. or the bad spelling of the comment above you lol

Rattsl (Feb 18, 2011 at 0:05)

Both hahahahaha

RideBikes927 (Mar 14, 2011 at 20:17)

just hit the jump like a man

benjiscott82 (Jun 28, 2011 at 15:31)

f*ck! maths makes me jizz

rangemaster Plus (Nov 16, 2011 at 21:05)

you need to bring statistics into this. you need a mean and about a 95% confidence interval. min being on cold days, maybe you are fat in the off season also, maybe your forks are stiffer in winter, the ground is harder AND max being in the summer, you are lighter maybe and your forks are plusher and the ground is dusty and loose. so once you figure out the formula for a proper jump in average conditions, you need to perfect it and make it foolproof. or don't, youtube might benefit from more crash videos.

[Reply]

+ 15

nickf (Mar 17, 2009 at 18:24)

does this mean i need a spedometer? i'll need to lock out my suspension, ride stiff armed and still legged. and i'll need my school supplies with me at all times. i'ld rather just huck

+ 15

angusmurray (Mar 17, 2009 at 23:19)

all you need is a tape measure, inclinometer, speedometer and calculator. i dont' see what the big deal is.

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+ 16

freeride11 (Mar 17, 2009 at 18:20)

+10 for being gnarly...

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birdman111 (Mar 16, 2009 at 16:41)

except you're not taking into account the suspension of the bike (regardless of how small the fork of a dirt jumper is) which changes the heights/distance the rider goes significantly.

angusmurray (Mar 17, 2009 at 23:17)

true, but still, most dj forks only have 100mm of travel so i wouldnt call the changes 'significant'.

the equation is based on the motion of a particle, and neglects factors like wind resistance, rotation, the movements of the rider, etc...

but it does give a pretty good indication of how fast you need to go.

audeo03 (Aug 3, 2009 at 8:36)

YOU are not taking into account that suspension is really JUST A SPRING and any energy input into them is put back out, minus friction... Conservation of Energy.

alech (Nov 15, 2009 at 9:28)

since when did bikes act the same way as particles Smile

lol

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paug (Apr 4, 2009 at 16:50)

Why's everyone talking about "taking into account rolling resistance"? It doesn't affect the formula at all because the velocity term is the v right at the lip of the jump. Any effects of rolling resistance would already have appeared, and are thus incorporated into the velocity term.

angusmurray (Apr 4, 2009 at 20:44)

spot on

[Reply]

+ 10

dirtparkstreet (Mar 17, 2009 at 18:20)

im so glad i never learnt physics, shits whack!

- 13

spongosauraus (Apr 5, 2009 at 12:36) (Below Threshold) show comment

i took higher physics and i hated it
so i dropped out half way through now when i look at my friends jotters its like
wow thts gay as heck im glad im out of there

+ 12

iainc92 (Apr 7, 2009 at 13:41)

sponge you fail. higher physics is awesome lol

- 15

spongosauraus (Apr 8, 2009 at 6:06) (Below Threshold) show comment

dropping physics was athe best thing ive ever done

dnbmx (Feb 21, 2011 at 6:15)

i got kicked out of a level physics :/

benjiscott82 (Jun 28, 2011 at 15:32)

did you forget to carry the 'x' too!?

[Reply]

someguy101 (Apr 12, 2009 at 2:00)

hmmm guess now when you hear them say "taking calculated risks" they are actually calculated.

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cornwallextreme (Aug 22, 2009 at 14:50)

How about the old formula

IF IN DOUBT, HIT IT FLAT OUT?

Usually works for me, plus i dont need a calculator and waste 10mins measuring and working out what i know the end product will tell me - PEDAL!!

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JamieT (Jun 2, 2009 at 14:26)

smart, but i prefer to use the cycle as fast as you can at a jump and hope for the best Smile

[Reply]

theGRIMreaper (Apr 7, 2009 at 18:56)

ahhhhhhhhh!!! im only a freshmen i cant figure it out, so does this mean i cant get good untill i can do math like that??

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sammie (Mar 25, 2009 at 15:15)

Nice one for trying. Looks pretty good to me. Although you have not taken into consideration the loss of momentum through air resistance and friction as you leave the ramp. There are a number of factors you have chosen to ignor, so your formula is not exact. But as mathematical models go.... good work.

angusmurray (Mar 26, 2009 at 3:40)

im working on a new model: one which incorporates wind resistance, rolling resistance, maybe fork compression, etc

shouldnt be too hard...

g3cko (Mar 26, 2009 at 11:18)

Oh my word - this is like an endless circle, it just gets more and more complicated.
then you're probably going to have to take into consideration all sorts of quantum wotzits Razz

sammie (Apr 9, 2009 at 5:21)

If you could get that done id be impressed. My maths unfortunately wouldnt be up to that right now lol. Give it a go and see how it goes.

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angusmurray (May 30, 2009 at 21:05)

well what you should have gotten was 11.9 m/s, because i just did the exact same thing -- but thats using the wrong equation

look up a bit and you see i made a mistake, so using your values....

v=7.2 m/s

both of these are real, i dunno what you did to get complex speed

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konastoner (Sep 16, 2009 at 7:49)

does that factor in if the riders shit?

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swampy45 Plus (Apr 17, 2010 at 18:37)

alright, i read about... 5 comments and got sick and tired of the bitchin'. Here's the deal. Grow some balls, strap on your full face, and just rock the gap already. who cares how big it is? DJ, DH, freeride... i dont care. if you clear it and land, good on ya. If you dont, get up, dust yourself, and push yourself back to run in or take the chair back up, and hit it again, until you DO clear it. BAM.

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henrytgreene (Apr 7, 2009 at 17:49)

POD

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Danger-Dan (Nov 19, 2010 at 14:56)

what about angles of the bike and fork hight for kick also the size of the person and there wind resistance.......also just get on your bike and hope for the best ride as fast as you dare or as fast as you think you need hoping for the best

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lafalot (Mar 12, 2011 at 19:12)

To all those who look at this and don't get it/think its redundantly complicated, your brain actually does this calculation in a fraction of a second if you've ever "eye-balled" a jump or thrown/caught a baseball.

[Reply]

da-hucker (Apr 15, 2010 at 11:59)

what a load of wa*k. get out and actually ride your bike you muppet lol

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Ompalompa (Jul 7, 2010 at 2:20)

Ok what about preload and suspension rates which could affect you take off?
I think you now have another few very complicated formulas to put in.
At least they are only linear equations though.

[Reply]

dh-andy (Aug 21, 2009 at 8:27)

ALL I CAN SAY IS....WTF! Eek

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vineet (Sep 15, 2009 at 10:11)

I'll be honest here. I flunked in maths in high school. Infact I have always been failing in maths ever since 4th grade.
So I have no clue about this stuff over here.. i just know there are some trignometry formulas here.. but what they prove.. i dont know dude.
But i know if there are 9 casettes at the rear wheel... and 2 chaingrings infront that = 18 speeds!

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caseygoulddhd (Mar 24, 2009 at 18:07)

wtf does any of that stiff meen????

g3cko (Mar 25, 2009 at 10:10)

haha - how fast you have to go to clear a jump Big Grin

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haighd2 (Nov 17, 2009 at 12:48)

very few ppl ride of jumps without pulling up so any figure you get out of this is goning to be way offf the mark.
stephen muarry put it best when he said "prettyshady ... you just got to pull back and yank"

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revsuicide (May 7, 2009 at 5:40)

You forgot about the Coriolis Effect lolol

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crazycody (Feb 2, 2011 at 14:49)

or you can just not be a pussy nerd and just pedal and hit it and see what happends Razz

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ratherbeoutriding (May 7, 2009 at 9:32)

ahh shit, now i cant use that "how is this going to help me in life" exuse in math class

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mrandt (Sep 17, 2009 at 6:57)

dude, i do trajectory questions like this all the time in physics! never thought to use one like this, physics is everywhere!

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luke-xcess (May 29, 2009 at 15:33)

you would have to take into account rotational energy or inertia because otherwise you could not go forwards on a jump with a vertical takeoff. Also you would have to have an imaginary velocity since you have the root of a negative number in there either that or the length of the gap would have to be complex (just try putting some numbers in and you'll see). also if you were to take the case where the take off and landing are the same height and the takeoff was vertical you would end up dividing by 0 since (y2-y1) would go to 0 as well as sin(theta)cos(theta) which also makes it all go strange.

angusmurray (May 29, 2009 at 18:41)

when you plug the numbers in you get the root of a positive number, whenever the difference between the heights (y2-y1) is less than the tangent of the theta. Also, theta has to be between 0 and 90 degrees. As you say, when theta equals 90 degrees, everything f*cks up, but thats because this particle sized bike rider would just go up and come straight back down, there is no rotational energy involved in this equation. Most jumps, even if they are extremely steep, don't go past 90 degrees, they might be at about 85 or something, but 90 is just silly.

So actually, for all theta between 0 and 90, and as long as the difference in the height is less than a meter (which is a reasonable assumption for most dirt jumps), you will not get a complex velocity.
so yeh

take that

luke-xcess (May 30, 2009 at 17:05)

I just stuck some numbers in (l=2.5, y2=2, y1=1.5 and theta=75) and it came out with 6.256983481i which is an imaginary number!?!?!?!

anthonysjb (Jun 6, 2010 at 12:01)

angus is right, makes perfect sense to me being an A* physics student Razz

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idonthaveabike (May 3, 2009 at 15:10)

and make sure you have a speedo on your bike....wont be able to know how fast you are going otherwise

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theriotact (Feb 6, 2011 at 12:14)

this hurts my brain more then it would hurt my brain to land hard. I think ill just hit it. Razz

Maxxis957 (Feb 7, 2011 at 14:18)

For real bro !

[Reply]

lux-freerider (Aug 25, 2010 at 8:54)

also you need to to take in account who the rider is because some of them just don't care about gravity and do whatever the hell they want....

arron-bighit (Nov 17, 2010 at 9:48)

depends which way the wind is blowing Razz

[Reply]

christian-shreder (Apr 4, 2009 at 7:53)

just grab a shovel and start digging

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gromhit (Mar 29, 2009 at 8:06)

wow,this guy is smart

onetimetwotime (Apr 3, 2009 at 7:06) (Below Threshold) show comment

no writing chinese on pinkbike.

benjiscott82 (Jun 28, 2011 at 15:40)

^^ hahaha

[Reply]

g3cko (Mar 24, 2009 at 10:10)

still, well done for trying - never mind what everyone else said!!! Big Grin

[Reply]

haroDHx6 (Nov 22, 2009 at 18:10)

when i see a jump, i hit it. I dont whip out a piece of paper..

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hodges (Apr 9, 2009 at 1:41)

i quit math!

[Reply]

jinx (Aug 3, 2009 at 8:46)

You haven't even included natural elements such as wind, ground material, tyre compound etc

mrandt (Sep 17, 2009 at 7:00)

yes, wind resistance, drag, momentum, Fg force of gravity, all of those shitties.

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parsons07 (Aug 17, 2009 at 13:14)

tbh hit the jump at the speed that feels right to you :L

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snook (Nov 17, 2009 at 12:38)

To be honest, it's cool, but you should just know by looking at the jump, if you're good enough.

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mhoenisch (Apr 7, 2009 at 14:06)

ur retarded just do the jump

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teuton612 (May 6, 2009 at 21:24)

If you are getting bad grades just think of that Haha or just show your teacher that and see if she understands it

[Reply]

lodonnell243 (Aug 6, 2009 at 16:23)

I'm proud of what I started. Smile

megastoked (Sep 4, 2009 at 20:36)

pretty entertaining.......and informative

[Reply]

rossspecialized (May 29, 2009 at 14:08)

or insted of goin to all that trouble just use the old sayin "practice makes perfect" Smile

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Jakerzzz (May 8, 2009 at 6:46)

Dude, i think its round about 9.81 mps Smile

[Reply]

Maxxis957 (Feb 7, 2011 at 14:18)

Or you could just pedal at a comfortable speed that you feel you'd clear the jump, huck it, then land ?

[Reply]

Mark-D (May 6, 2009 at 8:36)

i get it... i think????? lol

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ratherberidin (Apr 27, 2009 at 16:19)

does this include how high you pop or if you pump the jump

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JubaBabaci (May 21, 2010 at 14:08)

2+2=4 Now you have warmed up hit the jump!

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Nzide (Apr 23, 2009 at 10:10)

wooooo i coan work it out in the standard grade form lol

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JBR132 (Jan 5, 2011 at 15:47)

that has potential to be very useful, however it would help if anybody understood the answer!!!

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norcoryder11 (Apr 26, 2009 at 8:50)

you guys should be ashamed of your self. lol

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mountainbiker15 (Apr 22, 2009 at 19:28)

yeah like hole shit you guys get it right dam it its not that hard even look rofl Razz

[Reply]

pyro4826 (Nov 10, 2009 at 9:55)

time to put it into MATLAB Big Grin

[Reply]

wes101 (Jan 31, 2011 at 17:34)

thats not confusing at all

Maxxis957 (Feb 7, 2011 at 14:18)

Yes, it is.

wes101 (Feb 7, 2011 at 14:20)

lol i couldnt figure that out...

Maxxis957 (Feb 7, 2011 at 14:38)

Im looking at the stuff going "there's equations for riding" Likehonestly, just huck it !

wes101 (Feb 7, 2011 at 14:40)

wat about things like wind rain mud all varibles that can seriously mess u up in the air Razz

Maxxis957 (Feb 8, 2011 at 19:02)

Well, were talking nice bluebird sky days (Y) Lol.

[Reply]

z-man (Jul 28, 2010 at 13:23)

This proves how much smarter your trained unconscious mind is.

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Bikerboy290 (Sep 27, 2009 at 15:05)

its supposed to 9.81

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tyler-durden (Mar 12, 2011 at 19:23)

i find it quite funny that i actually understand most of this lol.

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gradester Plus (Mar 9, 2011 at 21:33)

Iunno wat that stuff means, but it means listen up in math

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woody-dh (Apr 26, 2009 at 21:30)

im not physicist but this looks pretty good to me

[Reply]

fooox (May 27, 2009 at 4:28)

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scottsrule (Apr 26, 2009 at 2:43)

u should be a land scaper

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freeride-assault (Apr 12, 2009 at 20:11)

wtf..................:-/

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lodonnell243 (Apr 15, 2009 at 18:27)

Motherf*ckers have taken this far too far Razz

[Reply]

jumpshot (Sep 16, 2009 at 13:03)

who gives a shit about all this!?

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Halzter (May 7, 2009 at 9:30)

Rather than work it out, just do the jump and go with the flow

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fireball-92 (May 9, 2009 at 9:53)

enough of the mathematical bollocks just get on with it !

Jakerzzz (May 9, 2009 at 14:27)

haha, yeah, but i felt like being smart for once lol

[Reply]

BeeAtherton (Aug 26, 2009 at 11:37)

mixing maths with biking.im not sure about that combination

mrandt (Sep 17, 2009 at 6:58)

physics has everything to do with biking.

[Reply]

AidenCrocker (Aug 28, 2009 at 2:59)

man the f*ck up .. sorted

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ari4 (Jul 7, 2010 at 1:25)

-y, what is this?

[Reply]

dougle08 (Jun 11, 2009 at 13:11)

you have to get out more

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sashamtbrider (May 18, 2009 at 21:04)

I HATE ALGEBRA LOL

TheAngryTomato (May 24, 2009 at 16:07)

THIS ISN'T ALGEBRA LOL

angusmurray (May 26, 2009 at 1:48)

technically it is algebra

TheAngryTomato (May 26, 2009 at 15:20)

yeah, the solving part of it but i'm talking about the actual formulation of the equation which is physics. sorry if that wasn't clear :/

[Reply]

hendu (Mar 22, 2009 at 21:01)

stop taking this shit so seriousley

nickf (Mar 22, 2009 at 21:03)

a speedometer with a sound box to tell your speed, duhhhh

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Below threshold threads are hidden

- 13

ryan879 (Mar 18, 2009 at 16:16)

i dont get all tht

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- 13

DH-rida-22 (Apr 19, 2009 at 14:46)

u guys are f*cking nerds who gives a f*ck biking has nothing to do with math

+ 11

angusmurray (Apr 20, 2009 at 0:08)

how dare you insult math

without it, your god-damn bicycle wouldn't exist in the first place

curlyaaron (Apr 22, 2009 at 12:45)

lol

TheAngryTomato (May 24, 2009 at 16:06)

word

math is the best

[Reply]

ThunderbirdDJ (Mar 23, 2009 at 17:54)

how about you just sack up and do the jump without all this crap

+ 23

angusmurray (Mar 24, 2009 at 1:49)

how about you lick my balls

BBtrails (Mar 26, 2009 at 13:16)

i will

woody-dh (Apr 3, 2009 at 18:08)

8-|

kqmtb2006 (Apr 7, 2009 at 14:54)

what the hell

fr112358 (Apr 22, 2009 at 19:44)

scrippsranchDJ (Oct 30, 2009 at 1:12)

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violetmetal (May 27, 2009 at 14:14)

the formula in hitting the jumps basically measures on how big are your balls....in dirt there's no physics thing...

angusmurray (May 27, 2009 at 22:01)

can you speak proper english?

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true-biker-face (May 24, 2009 at 23:29)

have you taken into account the psi of the tubes?

angusmurray (May 26, 2009 at 1:47)

makes no difference

true-biker-face (May 26, 2009 at 8:24) (Below Threshold) show comment

rolling resistance!

angusmurray (May 26, 2009 at 23:06)

this has been discussed so many times

it only matters how fast you are going when you hit the jump...

true-biker-face (May 27, 2009 at 7:08)

I was kidding.

BookerT88 (Mar 14, 2011 at 20:07)

Yes, but the tube compressing slightly can be seen as "preload". You must then take into account the elasticity and compressive strength of the tire tread.

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deathwish (May 29, 2009 at 14:06)

lovely formula, but it still doesnt tell you how fast you need to go

ukal (May 29, 2009 at 14:08)

just put there numbers...

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