Jumping - Better in higher or lower rpm's?

xenasdaddy

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Apr 8, 2001
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is it better one way or the other? i tend to hit jumps in a gear maybe too high and lower rpm's because i feel there is less chance of getting the front end too high, etc. do most mxer's choose a low gear in the meat of the powerband to go faster, etc?
xd
 

mx547

Ortho doc's wet dream
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Nov 24, 2000
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i generally jump just like you do. my reasoning is that it is usually better to try to carry momentum rather than to have the engine revved out (which is not necessarily going faster).
 

RM_Dude

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Jul 16, 2001
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I am a beginner and find that low to mid rpms in 3rd gear is sufficient for most jumps on my RM125. It seems I am now ready for the next level ,which in my mind is taking jumps in high rpms on the pipe. Have not tried this yet as I am trying to learn the brake tap really well first since that may very well be needed occasionally hitting jumps with high rpms. I'm thinking 4th gear pinned would be easy as the power of a 125 wouldn't be that extreme but I don't care to hit any jump going that fast. 3rd gear pinned seems pretty reasonable I think but I have a feeling it'll still try to loop out.

On the pipe in second gear is what I really want to be capable of. It seems allot of jumps at the local track could be done in top of second gear. Middle of third would probably work but unless you want to shift gears on face of the jump it isn't going to happen because the run up is very short just out of a turn.

I'm interested to see what some experienced riders can share about "on the pipe" jumping in second or third gear.
 

monkeybutt

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Jun 12, 2001
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Each jump is different and requires a different approach.I hit most jumps wide open and use my body to adjust on take off.Example,(dont try this on a big jump) I can go too fast for a small double and let off the throttle and pull in the clutch and take the jump with no throttle at all by using the correct body position and technique.Typically this is an advanced technique and is not for beginers!If you have never tried this,don't try it on a double and start real small and work your way up.
 

High Lord Gomer

Poked with Sticks
Sep 26, 1999
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I think lower power (low rpms) at higher speeds with more momentum is easier to learn for jumping, but when you get better you really need to be able to hit jumps on the pipe to get the most distance with the least running room.

It took me a long time to get over hitting everything in low 4th. Some doubles (40-55ft) that I make in mid 3rd I can easily overjump if I hit them on the pipe in 2nd.

I think there is less margin for error when hitting jumps at high RPMs, but you also have the ability to take the inside line and make the pass in many instances where people are used to going wide to get necessary speed.
 

Hucker

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Sep 15, 2000
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High Lord Gomer: I do the exact same thing, higher gear, lower rpm's. Makes it a bit easier to handle. I do agree however that sometimes you need to get on the pipe to get speed up, and 4th just ain't going to cut it...
 

Buzz Bomb

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May 9, 2000
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I am still trying to master jumping. It seems that when I hit a jump at high RPMs, the front wheel always wants to shoot up. Does this mean I'm leaning too far back? If I try to use less throttle, a don't get as much distance or lift it seems.
 

High Lord Gomer

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Sep 26, 1999
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Originally posted by Buzz Bomb
I am still trying to master jumping. It seems that when I hit a jump at high RPMs, the front wheel always wants to shoot up. Does this mean I'm leaning too far back? If I try to use less throttle, a don't get as much distance or lift it seems.
Exactly! The harder you are on the gas, the farther forward you need to be. Conversely, the harder you are on the brakes, the farther back you need to be.
 

RM_Dude

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Jul 16, 2001
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I can now hit jumps on the pipe in 3rd gear WHOOHOO !
but....
I don't have the throttle wide open on my 125 MXer, more like 3/4 throttle. Do you guys use wide open throttle while on the pipe for some jumps ?
 

FMX_novice

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Jan 5, 2001
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Acceleration off the face of the jump determines how far you go, and your attitude off the face. If you are at 10,000rpms 3rd gear WOT and accelerating like madness towards the face your gonna go flying. However if your in 3rd 10,000rpms letting off the throttle on the face your gonna go 20-30% shorter. The pros use this to there advantage by going up to a jump that can be cleared in 3rd gear, in 4th. Then they hit there brakes on the face and clear it and go faster thru the straight. You want to use the landing of the jump to conserve energy and have gravity work for you like a downhill ramp to gain speed off of. make sure you dont crack the throttle in 1st because 33 horses pushing a gear that small makes you look like carey harts little brother.
 

motopuffs

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Mar 15, 2001
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In theory, your bike is more stable in the air in a lower gear with higher revs due to the gyroscopic forces of the rotating mass (crank, flywheel, etc.).

A 250 (the kind that burn premix) really leaves you more options than 125s, because it doesn't matter so much how high you are revving. 125s like to be on the pipe when taking off. If you haven't mastered this yet, it is important to work on. The next step is clutching it on the take off, such as if you misjudged a bit, or don't have a run at it.

Whatever you do, work your way into trying new techniques. Tables are more friendly than doubles, of course.

To answer your question RM DUDE, I use wide open throttle and clutching all the way up the ramp on my 250, under certain rare conditions. It's all about body positioning and also being able to adjust the attitude of the bike while in the air.
 

FMX_novice

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Jan 5, 2001
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It seems that when i jump i need to use the middle of the gear, if i go too high i land all the way on the back wheel, if i bog it i just dont go anywhere. If i let off the gas the bike doesnt really respond, if i hit the gas in the air i cant tell a difference either. I hit the big jumps its just that the way i go up it the way i come down, :scream: . Im going to try hitting the jumps on the pipe and leaning over the bars so i can see my numbers. Its probobly that i have a neutral jumping position and im to stiff in the air to move.
 

funktree

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Jul 21, 2001
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A good way to practice this is to find a smallish tabletop you are completely comfortable with. Try jumping it all sorts of different ways. I used to have a 40' tabletop on my yard that I could clear in first second or third. I kept trying to jump it with less and less runway. I eventually got to the point where I could jump it from a dead stop about 15 ' from the face, in first gear sitting down. Dont try the sitting down thing yet though.
 

FMX_novice

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Jan 5, 2001
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In theory, your bike is more stable in the air in a lower gear with higher revs due to the gyroscopic forces of the rotating mass (crank, flywheel, etc.).
Explain this theory please, as i understood it, the bikes acceleration at higher revvs would cause it to point at the sky...?
 

Yz426King

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Aug 18, 2001
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The crank, flywheel, etc. will create gyroscopic forces much like a spinning top. If you spin a top slower vs spinning one faster, the fast one will be harder to tip on its side. Same way with a bike. Have you ever played with a bicycle wheel when it was off the bike. Hold it by the axle and spin it slowly, then try to turn it on sideways, then try it spinning fast. You will know what I mean then.
 

FMX_novice

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Jan 5, 2001
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Ohh ok, yeah, now i remember back in 6th grade(5 years ago) the teacher with some roadracing bicycle wheel and he had a kid hold it and he spun it and it was really tough for him to turn. Too bad he didnt have the kid hold it like a swingarm and have it pivot like a suspension. Hmm, time for some experimentation...
 

motometal

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Sep 3, 2001
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I'm pretty sure the gyro effecto only applies perpendicular to the axis of rotation. In other words, this would tend to keep your bike going straight thru the air, but would have zero effect on how high or low your front end is.
 

ktmboy

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Apr 1, 2001
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Motometal- Have you ever grabbed your front or back brake while in the air? Have you ever done a panic rev? Either one of these manuevers will give you a quick lesson in gyroscopic forces. Think about it: when your bike leaves the ramp both wheels are traveling about the same speed / RPM. Now slow down or speed up one wheel. The attitude of your bike will change. Panic rev, back wheel drops; front or back brake, front wheel drops.
 

High Lord Gomer

Poked with Sticks
Sep 26, 1999
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Originally posted by ktmboy
Motometal- Have you ever grabbed your front or back brake while in the air? Have you ever done a panic rev? Either one of these manuevers will give you a quick lesson in gyroscopic forces.
Bzzt, wrong answer. Motometal was right about gyroscopic forces being perpendicular.

While you are right about the behavior of the bike, it is not a result of gyroscopic forces. I think it is something like the transfer of rotational (or is it angular) momentum.

Now, someone please correct me.
 

ktmboy

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Apr 1, 2001
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You're probably right- I was better in the arts than math or science. I never really cared how it worked as long as it worked. :o
 

Jaybird

Apprentice Goon
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:think Hmmm....
I think that this does deal with gyroscopics. The reaction of the bike when you alter the speed of the spinning wheel deals with gyroscopic momentum.
Mass and velocity are the keys, and how they effect the gyration of a spinable object (bike) that has a seperate spinning object attached to it (wheel). Which in effect makes your bike a gyroscope of sorts.

I may be just spinning my wheels with this though. :)
 
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motometal

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Sep 3, 2001
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I'm not sure about the official definition, but discussions regarding gyroscopic forces are generally referring to the resistance of a spinning mass to movement in a plane perpendicular to the axis of rotation, with the spinning mass staying at a constant speed.

Yes, actually I have tried hitting either brake in the air, and this is a quick lesson in conservation of momentum and transferring momentum about an axis. Extra credit quesion: if you hit both brakes, would the forces cancel each other out (at least to some degree)? Think about it, the rear is trying to rotate on its axis, and same with the front. This would create opposite torque reactions on the bike, I think. My gut feeling is that the fron end would still drop, but how much in relation to either brake by itself, I don't know.

By the way, the front brake in the air thing is a bit risky...I've only tried this on small doubles with nice landing ramps. Not something I recommend trying unless you are sure of yourself.

Nerdy science stuff is cool!
 

FMX_novice

Member
Jan 5, 2001
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If a bike is more stable, does that mean its less likely to change pitch from parallel to the ground? I have never went off a jump straight no matter how low the rpms and landed sideways. The key is, in what RPM's is the bike most perpendicularly stable. Since the rear wheel will increase its speed at a faster rate in the heart of the powerband i think the bike would be less perpendicularly stable at high RPM's. Also the brake would have a more dramatic effect at higher speeds.
A jump in 4th gear mid will have good stability, perpendicular and parallel to the ground because the wheel is spinning fast, keeping the rubber side down, and the bike will rev slower because it is producing less power on the low RPMs'.
Now, i want everyone to go out this weekend and find the biggest double and hit it in 6th gear pinned, tell me how stable the bike is, or have your priest post a copy of your eulogy here. :p
 

ktmboy

~SPONSOR~
Apr 1, 2001
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Ah, scientists; ya gotta love 'em. Why, without nerdy scientists, the wonderful alloys that make up my bike and the modern, more effective pre-mixes would not exist!:)
 

Hogwylde

Member
Aug 1, 2001
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Originally posted by motometal
Extra credit quesion: if you hit both brakes, would the forces cancel each other out (at least to some degree)? Think about it, the rear is trying to rotate on its axis, and same with the front. This would create opposite torque reactions on the bike, I think.


the answer to the extra credit question is NO, the forces would NOT cancel, but ADD. think about it. both wheels are turning in the same direction (fwd). if you hit the front brake, it will try to rotate the bike in the fwd direction. the rear wheel is also rotating in the fwd direction and would try to rotate it fwd also. BUT, you do have two different axix of rotation. if you just use the front brake, you will try to rotate around the front axle. if you just use the rear brake, you will try to rotate around the rear axle. if you use both brakes, you will try to rotate around a point somewhere in between. SO, what u end up with is this. just using the front brake will tend to RAISE the rear end. just using the rear brake will tend to LOWER the front end. and using both brakes will tend to rotate the bike evenly from a point in the middle of the two axles.
 
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