Seat bounce

FWYT
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6/12/2020 7:37am
wildbill wrote:
I hit a false neutral once while doing this. Not fun.
hahahah No kidding!
Forty
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6/12/2020 7:40am
Someone call Kevin Windham.
FWYT
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6/12/2020 7:57am
Anyone else been ripping across the desert and hit a G-out they weren't ready for?

And?

Not sure of the science. I always attributed getting tossed over the bars from shitting my
pants so hard it caused a massive forward and vertical thrust. I could be wrong.LaughingLaughing
5

The Shop

mxracer666
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6/12/2020 8:11am
aees wrote:
It is not the same thing. You have several Gs in force that you experience when you go into a jump face, not so much on...
It is not the same thing. You have several Gs in force that you experience when you go into a jump face, not so much on flat ground.

It is a combination of loading the suspension with body position and throttle, as well as taking weight of the seat just before wheels leave the jump face and lifting the bike a bit since you move fwd in the process.

If seat bounce does not work, neither does scrubbing or absorbing suspension travel with legs since it is the direct opposite of seat bounce.

Two persons going up a jump face all things being equal, one will seat bounce I promise you that bike if going higher then the other.

Extra height is typically what you want when seat bouncing, so you don't run the front wheel to short coming into landing or next jump.
abn166 wrote:
I don't think anyone said seat bouncing doesn't work. It just doesn't work by using the shock as some sort of pogo stick as some seem...
I don't think anyone said seat bouncing doesn't work. It just doesn't work by using the shock as some sort of pogo stick as some seem to think.


"It is a combination of loading the suspension with body position and throttle, as well as taking weight of the seat just before wheels leave the jump face and lifting the bike a bit since you move fwd in the process."

Look at the photo of Eli, he is not taking his weight off of the seat just before the wheels leave the ground. No one seat bounces that way.


aees wrote:
He does, a micro second later just before or at the same time the shock start to rebound. If he don't, he is going to the...
He does, a micro second later just before or at the same time the shock start to rebound. If he don't, he is going to the moon.
I don't think you have personally mastered the "seat bounce " technique. Keep practicing.
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rjg
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6/12/2020 8:16am Edited Date/Time 6/12/2020 8:34am
The whole seat bounce thing is easy. The rider makes the Suspension as much collapsed as it can be at the given moment and times it so a rigid frame is riding the jump face. It makes it so there is the smallest amount of bump is absorbed.

Scrubbing keeps you lower because the rider is initiating a down ward trajectory (falling over sideways) to take away from the upward trajectory. It makes the wheels/bike/rider lighter in a sense. That along with the bike leaving the jump face earlier in its slope, you are not riding the jump face as high and long.
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mxracer816
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6/12/2020 8:50am
I would assume this theory has a lot to do with the why...."for every action there is an equal and opposite reaction"
The more energy you push into the bike and face of the jump the more energy is released when leave the face of the jump. Just my take, and I'm no engineer, but seems reasonable to me.
350ss
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6/12/2020 9:09am
i really wish i could find this but there is an america's funniest home videos clip where a guy on the streeet is wheeleing a cr500 and slips off the back and compresses the suspentsion and when he lets go the bike shoots about 10-15 feet in the air... how does this happen if the spring rebound doesn't cause it
ns503
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6/12/2020 9:11am
EngIceDave wrote:
A TFS experiment (physical or mental) If you took your motorcycle and four (4) tiedowns, and compressed your bike's suspension as far as possible, and were...
A TFS experiment (physical or mental)

If you took your motorcycle and four (4) tiedowns, and compressed your bike's suspension as far as possible, and were able to simultaneously release all four tiedowns, all at once....

Will the bike leap up off the ground several inches, actually getting "air," or would the shocks just rebound the bike to its standard position?
aees wrote:
It is not the same thing. You have several Gs in force that you experience when you go into a jump face, not so much on...
It is not the same thing. You have several Gs in force that you experience when you go into a jump face, not so much on flat ground.

It is a combination of loading the suspension with body position and throttle, as well as taking weight of the seat just before wheels leave the jump face and lifting the bike a bit since you move fwd in the process.

If seat bounce does not work, neither does scrubbing or absorbing suspension travel with legs since it is the direct opposite of seat bounce.

Two persons going up a jump face all things being equal, one will seat bounce I promise you that bike if going higher then the other.

Extra height is typically what you want when seat bouncing, so you don't run the front wheel to short coming into landing or next jump.
Ah but it is the same thing (the tie down thing), as far as the springs are concerned. They only have so much force absorbing capability. Whether being collapsed by tie downs, or hitting a jump. Once they are collapsed, any extra force needs to go somewhere else. On a jump, that extra force sends you up.
abn166
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6/12/2020 9:13am
350ss wrote:
i really wish i could find this but there is an america's funniest home videos clip where a guy on the streeet is wheeleing a cr500...
i really wish i could find this but there is an america's funniest home videos clip where a guy on the streeet is wheeleing a cr500 and slips off the back and compresses the suspentsion and when he lets go the bike shoots about 10-15 feet in the air... how does this happen if the spring rebound doesn't cause it
That is completely impossible for a shock to do that even without dampening. Sounds like whiskey throttle to me.
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aees
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6/12/2020 9:30am
EngIceDave wrote:
A TFS experiment (physical or mental) If you took your motorcycle and four (4) tiedowns, and compressed your bike's suspension as far as possible, and were...
A TFS experiment (physical or mental)

If you took your motorcycle and four (4) tiedowns, and compressed your bike's suspension as far as possible, and were able to simultaneously release all four tiedowns, all at once....

Will the bike leap up off the ground several inches, actually getting "air," or would the shocks just rebound the bike to its standard position?
aees wrote:
It is not the same thing. You have several Gs in force that you experience when you go into a jump face, not so much on...
It is not the same thing. You have several Gs in force that you experience when you go into a jump face, not so much on flat ground.

It is a combination of loading the suspension with body position and throttle, as well as taking weight of the seat just before wheels leave the jump face and lifting the bike a bit since you move fwd in the process.

If seat bounce does not work, neither does scrubbing or absorbing suspension travel with legs since it is the direct opposite of seat bounce.

Two persons going up a jump face all things being equal, one will seat bounce I promise you that bike if going higher then the other.

Extra height is typically what you want when seat bouncing, so you don't run the front wheel to short coming into landing or next jump.
ns503 wrote:
Ah but it is the same thing (the tie down thing), as far as the springs are concerned. They only have so much force absorbing capability...
Ah but it is the same thing (the tie down thing), as far as the springs are concerned. They only have so much force absorbing capability. Whether being collapsed by tie downs, or hitting a jump. Once they are collapsed, any extra force needs to go somewhere else. On a jump, that extra force sends you up.
You are considering the shock to be the only thing that is absorbing the energy going into a jump face/seat bouncing, it is not. The whole bike including your body acts as a catapult moving mass from rear of bike and forward ones in the air.

Normal jumping, or jumping and absorbing the energy with your legs going into jump faces typically don't drive suspension and bike all the way to the limit as you do when seat bouncing.

Try seat bounce with a softer rear spring that runs full stroke already when front wheel hits the bottom of jump face = no difference from jumping regular. You can way faster and more aggressive into jumps with to soft springs since there is limited rebound effect.
abn166
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6/12/2020 9:41am
Still, the shock does not rebound until the bike has left the ground. So it cannot act like a pogo and push someone higher into the air. That is not what is happening when someone seat bounces.
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avidchimp
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6/12/2020 9:41am
Somewhere up there Bruhn is laughing his ass off at this.

Damn I miss that guy. So many epic discussions/arguments at the races and on the old boards.
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aees
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6/12/2020 10:02am
abn166 wrote:
Still, the shock does not rebound until the bike has left the ground. So it cannot act like a pogo and push someone higher into the...
Still, the shock does not rebound until the bike has left the ground. So it cannot act like a pogo and push someone higher into the air. That is not what is happening when someone seat bounces.
Normally it starts to rebound when you take weight of rear, which you do just before the rear wheel leave the ground, not to loop out on short jumps with little air time.

Only time I hold the rear end compressed all through the jump face is when I need to get extra clearance for the front wheel l, like placing it up on top of a big step up when jump face I take of from is to level.

The longer you hold the rear end down, the steeper the angle of your trajectory is which means easier to at least get the front wheel on top of the last jump.

Changing the trajectory is of course part of the normal seat bounce but to lesser extent than above.

Good example was this week's jump before finish line. Guys needed height, not only distance, to avoid double bounce before passing finish line.
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aeffertz
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6/12/2020 11:06am
This is ridiculous.... wow.

Carry on.
You should’ve seen the which way is this rider whipping thread!
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Pink
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6/12/2020 11:41am
seth505 wrote:
Force...potential energy. There is more at play than the rear shock. Shove the bike into the face of the jump so the suspension collapses, the frame...
Force...potential energy. There is more at play than the rear shock. Shove the bike into the face of the jump so the suspension collapses, the frame and chassis parts flex extra hard...That causes a reaction that will absolutely boot you up on a higher trajectory.

How do people think you can pump a bicycle when it has no shocks and no motor, yet you can pick up speed without pedaling?
Ding ding ding. Remove you suspension and insert steel rods. This would give you the ultimate ”seat bounce”. Your suspension just tries to absorb the jump.
-MAVERICK-
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6/12/2020 12:59pm Edited Date/Time 6/13/2020 8:22am
This is ridiculous.... wow.

Carry on.
aeffertz wrote:
You should’ve seen the which way is this rider whipping thread!
Grinning Definitely to the right...

Edit: You started that whole shit show, lol.
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davis224
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6/12/2020 1:02pm
I'd just like to note that this has remained somewhat civil with nobody taking it personally yet. Let's keep it that way and just have a healthy debate where we make points and present evidence!

Now, who has a good slomo video of someone seat bouncing?
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Mr. Afterbar
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6/12/2020 1:02pm
There's more than one way to seat bounce a jump. Sitting down into the bottom of the jump will absolutely have a rebound effect. Sitting down into the top of the jump will help you get the front end up, but not have the same pop as sitting down lower into the face. As for what's actually causing the reaction bike wise, I'll leave that for the rest of you to argue about.
6/12/2020 1:14pm
This is great, we all keep "bouncing" back and forth...

The simplest and most accurate explanation is a combo of several things already mentioned.

1. harder than normal acceleration results in higher speed at liftoff
2. rear of bike is compressed further than normal due to rider weight back, "smashing" it down
3. angle of attack off end of takeoff ramp is higher due to rear of bike being lower
4. all of the above results in a higher trajectory, thus being able to travel further in the air

gt80rider
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6/12/2020 1:38pm Edited Date/Time 6/12/2020 1:39pm
Gosh dern do I love seat bounce threads . . ! They always deliver!
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davis224
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6/12/2020 1:56pm
Who remembers the thread about if an airplane can take off if the runway was a treadmill that runs faster than the plane can fly? There were pilots who didn't think it could.
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abn166
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6/12/2020 2:10pm
davis224 wrote:
I'd just like to note that this has remained somewhat civil with nobody taking it personally yet. Let's keep it that way and just have a...
I'd just like to note that this has remained somewhat civil with nobody taking it personally yet. Let's keep it that way and just have a healthy debate where we make points and present evidence!

Now, who has a good slomo video of someone seat bouncing?
Go into the settings on the video posted above and set it to view on the slowest setting. You will clearly see the suspension rebounds after the bike leaves the ground. And the rider does not stand up until after he leaves the ground which is typical. The rear shock clearly is not pushing the bike and rider higher and or farther. Seat bouncing works but just not for the reason most people choose to believe.
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RonJon516
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6/12/2020 2:14pm Edited Date/Time 6/12/2020 2:17pm
Here is a quick video of Doug Henry seat bouncing a very technical double, triple last week. He said that’s what slows him down because he has to seat bounce all the jumps lol . Dude is amazing and still rips

Edit: damn I don’t know how to put video on Sad
aees
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6/12/2020 2:24pm
davis224 wrote:
I'd just like to note that this has remained somewhat civil with nobody taking it personally yet. Let's keep it that way and just have a...
I'd just like to note that this has remained somewhat civil with nobody taking it personally yet. Let's keep it that way and just have a healthy debate where we make points and present evidence!

Now, who has a good slomo video of someone seat bouncing?
abn166 wrote:
Go into the settings on the video posted above and set it to view on the slowest setting. You will clearly see the suspension rebounds after...
Go into the settings on the video posted above and set it to view on the slowest setting. You will clearly see the suspension rebounds after the bike leaves the ground. And the rider does not stand up until after he leaves the ground which is typical. The rear shock clearly is not pushing the bike and rider higher and or farther. Seat bouncing works but just not for the reason most people choose to believe.
Wheel Still on the ground, but suspension has started to rebound several inches compared to complete bottom out. So it absolutely has a vital part.

If you have been testing rear shock suspension and going back and fwd between spring rates is becomes very obvious. If I setup a 42 spring with 10mm preload I can set up a tent on my rear fender and camp there during take off and still come up short/low, not much help. If I put on a 50nm with 5mm preload and even hint at seat bouncing I will find myself flat landing a bike length to long on the same jump.


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abn166
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6/12/2020 2:36pm
The small amount of rebound that has occurred since the rider reached the face of the jump will not affect the height or distance of the jump. below is the rider 5 feet into his jump. As you can see now he is standing and the suspension has rebounded while the bike was in the air.
FWYT
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6/12/2020 4:25pm
davis224 wrote:
I'd just like to note that this has remained somewhat civil with nobody taking it personally yet. Let's keep it that way and just have a...
I'd just like to note that this has remained somewhat civil with nobody taking it personally yet. Let's keep it that way and just have a healthy debate where we make points and present evidence!

Now, who has a good slomo video of someone seat bouncing?
It would be awesome if one of those "physics explained" type of YouTube channel people did a thing
on seat bouncing.
TeamGreen
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6/12/2020 5:05pm
davis224 wrote:
I'd just like to note that this has remained somewhat civil with nobody taking it personally yet. Let's keep it that way and just have a...
I'd just like to note that this has remained somewhat civil with nobody taking it personally yet. Let's keep it that way and just have a healthy debate where we make points and present evidence!

Now, who has a good slomo video of someone seat bouncing?
FWYT wrote:
It would be awesome if one of those "physics explained" type of YouTube channel people did a thing
on seat bouncing.
Science of Supercross with Adam doing the riding & MC explaining it (360 global view frozen/stop action and MC walks into the frame & explains what’s goin’ on at different points in the action: set-up, squat/compress, ramp to launch...& take off).

It needs to be one of those turns that’s right at the exit of a 180 SX “bowl turn” at a ATL or Dallas SX type track.

Not that I have an opinion on the matter...
Laughing
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