# What causes unintentional tail-whip

47 replies to this topic
• # Chills

Posted July 11, 2005 - 08:58 AM

DaveJ,

In reference to Ashes, and the rear wheel kickin out, this refers back to not being squared up with the jump. Whether your rebound is too much or too little doesnt matter. You nailed it when you said the rear tire will take the path of least resistance. Hence if you were squared, it would kick the rear tire up above the front and you would be nosing down, which is corrected with more throttle to bring the front end up while airborn. If you are leaning, even slightly, the rear will tend to drift opposite of the way you are leaning, thus the path for least resistance. If he is squared to the face of the jump, hits it, and the rear starts to drift on him, only 2 things seem reasonable... Wind or sprocket misalignment. If he was squared with the jump, rebound or damper would cause either nose over or nose high, either the engery would kick the rear end UP, or not enough engery and the front would be higher. There is no formulation being squared to a jump that the engery shouldnt be linear with the bike unless something was out of line. Now whether the rider thinks he is square or not is another story...

• # DaveJ

Posted July 11, 2005 - 11:16 AM

If he is squared to the face of the jump, hits it, and the rear starts to drift on him, only 2 things seem reasonable... Wind or sprocket misalignment. If he was squared with the jump, rebound or damper would cause either nose over or nose high, either the engery would kick the rear end UP, or not enough engery and the front would be higher. There is no formulation being squared to a jump that the engery shouldnt be linear with the bike unless something was out of line.

My main point earlier, involving the alignment matter, was that the rear end of the bike could not travel beyond the degree in which the wheel is out of alignment. For example, if the rear wheel was tilted in the swing arm at 10 degrees, then the rear kick would not exceed that same 10 degrees (when in the air) unless other forces where in play.

Why? Because that 10 degrees is a physical boundary in which the energy from the drive train would cause the rear wheel to kick to one side.

Now, if you had a wheel that was 10 degree off, AND you have little to no rebound damping, you have then introduce another energy source contributing to rotating the bike...that of course is the rapid decompressing of the spring. In effect, the tilted wheel acts as a "trigger" that directs and amplifies the rebound problem.

This also means that a rider or mechanic that aligns a crooked wheel, on a kicking bike, may seemingly alleviate a whipping problem, but that does not mean that they have solved the matter of too little rebound damping.

With that, I'm saying that you should not assume that any environment is so perfect that this rebound matter (too little rebound) would always present itself as a bike that seems to dive in mid-air.

DaveJ

• # johnmeasures

Posted July 11, 2005 - 12:55 PM

If the bike is the cause could consider:
Too much preload on the rear spring ?
Spring too powerful ?
Too much compression on rear shock ?
If the rider is the cause could consider:
Get some photos of the stunt before you bite the dirt! *grin*

• # MWB

Posted July 11, 2005 - 08:41 PM

where does one find the alignment tool you speak of, as i cant even hardly see my hash marks on my bike

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
• # MattyH

Posted July 12, 2005 - 05:19 AM

Have your wheels balanced, as unbalanced wheels can have a gyroscopic effect and cause the whip effect. The weight of the rimlocks tends to be responsible for this and using balancing weights will correct it. Any bike shop should be able to balance your wheels or you could do it yourself with a small selection of 20 and 25gram lead weights and a set of pliers.

• # DaveJ

Posted July 12, 2005 - 01:06 PM

Here's a good video that shows a clear distinction between riders that have enough rebound and those that don't.

http://www.thumperta...ad.php?t=272692

The only other thing that needs adjusting is the person that chose the music.

• # AMCA_BRISTOL_SPARTANS_66

Posted December 27, 2005 - 12:12 PM

maybe your back wheel isnt straight, i no that sounds kind of stupid but maybe when you've pulled your wheel back to tighten the chain, you might not have lined it up equal on both sides, use the lines on the swing arm to get an equal reading. if your wheel isnt straight when your in the air it will spin on an angle causeing your tail to come around (tail whip!)

• # jrcgaf364

Posted December 27, 2005 - 04:24 PM

Check to see if your wheel is aligned correctly.

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