Seat bounce

mulletman wrote:

I think you’re a very good writer who has duped most people on here lol. The table to table argument doesn’t involve seat bouncing. All the...

I think you’re a very good writer who has duped most people on here lol.

The table to table argument doesn’t involve seat bouncing. All the ones I remember involved standing and most had a slight incline at the end. I also remember how many rear wheels clipped the face of the next table. And are you saying that jumping up and landing on a tabletop can cause a bike to bounce, but Tomac and crew airing it out over HUGE singles and flat landing doesn’t cause the same reaction? Both situations is a flat landing with the riders on the throttle. I’ve seen this with sx and mx suspension with the same reaction.


Here’s the only “moments in time” that matters. Look at the rear shock. Compressed until the same time you see the tire rebound to its original shape,
which is when the rear wheel leaves the ground.

Falcon wrote:

Again, timing. Are you telling me that Tomac couldn't bunny hop or time his landing in such a way as to make the bike bounce after...

Again, timing. Are you telling me that Tomac couldn't bunny hop or time his landing in such a way as to make the bike bounce after landing? Does his own mass and inertia not have any effect on the motorcycle? Clearly it does. I'd be willing to bet he could land from a single jump and use the rebound from the suspension to lift the bike substantially. This is what I suspect is happening in the tabletop to tabletop reference. You've seen video of somebody landing in slop, coming to a dead stop and then getting sprung up and over his bars, no doubt? Not all of that is the result of his forward momentum.

Seat bouncing works because riders time the release of the spring to coincide with their upward momentum, thus pairing their own mass to the bike's. They can just as easily cancel out the spring by standing and soaking up some of the upward momentum with their legs and/or turning the bike at the right time. (Scrub to stay low, seat bounce to go high.)

I'd like to see more pictures like the ones above, done in several passes, some standing and some sitting. I think they would illustrate what I'm saying: that the shock can be purposely compressed more by the rider's judicious application of weight at the right time; that it travels downward until a specific point in time, when it begins to return (and does not remain "compressed" the entire time up the jump face, but rather begins to rebound); and that a skilled rider can time those events to minimize or maximize the upward velocity from the energy returned by the shock spring.

mulletman wrote:

A bunny hop is not the same thing as a seat bounce. You are literally snatching up on the bars. I’m no pro, but I’ve seat...

A bunny hop is not the same thing as a seat bounce. You are literally snatching up on the bars. I’m no pro, but I’ve seat bounced many things and never once tried to lift the bike or “time” anything. Not to mention, I’ve seen the pros seat bounce with their inside foot off the peg. Seems like it would be hard to “re-couple” or whatever with the bike with one leg hanging off.

You mention mass of rider. Why? Projectile motion doesn’t care about mass. The bike is bottomed out and doesn’t unload until you’re off the face, so it doesn’t matter if you weigh 150lb or 200lb. All that matters on take off is speed and launch angle. And that’s exactly what seat bouncing gives you more of.

I’ve already posted pics (literally the first video I found on YouTube) and you’re basically ignoring the fact it shows exactly what I’m saying.

Last thing, if it really is the rear shock springing back that causes extra distance, then:

1. Why doesn’t the bike nose over immediately if all the force is being provided from the rear spring?

2. At what point would the shock begin to unload and why do we not see wheel spin at some point on the jump face?

mulletman wrote:

I think you’re a very good writer who has duped most people on here lol. The table to table argument doesn’t involve seat bouncing. All the...

I think you’re a very good writer who has duped most people on here lol.

The table to table argument doesn’t involve seat bouncing. All the ones I remember involved standing and most had a slight incline at the end. I also remember how many rear wheels clipped the face of the next table. And are you saying that jumping up and landing on a tabletop can cause a bike to bounce, but Tomac and crew airing it out over HUGE singles and flat landing doesn’t cause the same reaction? Both situations is a flat landing with the riders on the throttle. I’ve seen this with sx and mx suspension with the same reaction.


Here’s the only “moments in time” that matters. Look at the rear shock. Compressed until the same time you see the tire rebound to its original shape,
which is when the rear wheel leaves the ground.

Falcon wrote:

Again, timing. Are you telling me that Tomac couldn't bunny hop or time his landing in such a way as to make the bike bounce after...

Again, timing. Are you telling me that Tomac couldn't bunny hop or time his landing in such a way as to make the bike bounce after landing? Does his own mass and inertia not have any effect on the motorcycle? Clearly it does. I'd be willing to bet he could land from a single jump and use the rebound from the suspension to lift the bike substantially. This is what I suspect is happening in the tabletop to tabletop reference. You've seen video of somebody landing in slop, coming to a dead stop and then getting sprung up and over his bars, no doubt? Not all of that is the result of his forward momentum.

Seat bouncing works because riders time the release of the spring to coincide with their upward momentum, thus pairing their own mass to the bike's. They can just as easily cancel out the spring by standing and soaking up some of the upward momentum with their legs and/or turning the bike at the right time. (Scrub to stay low, seat bounce to go high.)

I'd like to see more pictures like the ones above, done in several passes, some standing and some sitting. I think they would illustrate what I'm saying: that the shock can be purposely compressed more by the rider's judicious application of weight at the right time; that it travels downward until a specific point in time, when it begins to return (and does not remain "compressed" the entire time up the jump face, but rather begins to rebound); and that a skilled rider can time those events to minimize or maximize the upward velocity from the energy returned by the shock spring.

mulletman wrote:

A bunny hop is not the same thing as a seat bounce. You are literally snatching up on the bars. I’m no pro, but I’ve seat...

A bunny hop is not the same thing as a seat bounce. You are literally snatching up on the bars. I’m no pro, but I’ve seat bounced many things and never once tried to lift the bike or “time” anything. Not to mention, I’ve seen the pros seat bounce with their inside foot off the peg. Seems like it would be hard to “re-couple” or whatever with the bike with one leg hanging off.

You mention mass of rider. Why? Projectile motion doesn’t care about mass. The bike is bottomed out and doesn’t unload until you’re off the face, so it doesn’t matter if you weigh 150lb or 200lb. All that matters on take off is speed and launch angle. And that’s exactly what seat bouncing gives you more of.

I’ve already posted pics (literally the first video I found on YouTube) and you’re basically ignoring the fact it shows exactly what I’m saying.

Last thing, if it really is the rear shock springing back that causes extra distance, then:

1. Why doesn’t the bike nose over immediately if all the force is being provided from the rear spring?

2. At what point would the shock begin to unload and why do we not see wheel spin at some point on the jump face?

Falcon wrote:

Seat bouncing would not require both feet on the pegs. "Coupling" of yours and the bike's inertia happens because of body position relative to the bike's...

Seat bouncing would not require both feet on the pegs. "Coupling" of yours and the bike's inertia happens because of body position relative to the bike's while leaving the jump face. Either you are maximizing it (going together as one) or minimizing it (moving the masses in separate directions as much as possible.)

Projectile motion absolutely cares about mass in this sense: F=MA. When you increase the force in the equation, the acceleration increases. There's your speed increase and your change in trajectory. By compressing the spring more, you are providing more potential to it, which is returned as greater force.

I don't agree that the videos show exactly what you are saying.

"All" the force is not created by the rear spring. Of course not. Most of it is the momentum of the bike, brought to you by your friendly neighborhood internal combustion engine and the redirection thereof by the jump itself.

The shock begins to unload as soon as the force acting on it to compress is smaller than the shock's stored potential. It may not return to full travel at the bottom of the jump face, but as soon as it is rebounding, it is applying acceleration.

kkawboy14 wrote:

[img]https://p.vitalmx.com/photos/forums/2020/06/20/433361/s1200_4CF28303_93F6_4337_824E_1927581473B4.jpg[/img]