What Causes Headshake?


29 replies to this topic
  • Robert_Brazil

Posted February 20, 2005 - 10:32 AM

#21

Set your SAG at 4" and out your forks at the lowest position in the clamps, this opens your caster angle, reducing headshake chanches at high speeds, also make sure your front wheel is not bumped, you could also statically balance it to reduce inbalance, that induces the headshake. If you ride al the time at high speeds a (scotts/ohlins) damper is recommendable

  • Dan_from_HB

Posted February 20, 2005 - 06:54 PM

#22

A stabilizer may cover up / compensate for the headshake issues, but I'd get to the root of the problem first and fix it before considering a stabilizer.


Amen. Stabilizers are great, but they do hide some problems. A good one will take care of the headshake, but if the basic suspension setup is wrong, the handling will always be a little goofy.
THEN get a stabilizer.

  • WRider995

Posted February 20, 2005 - 07:58 PM

#23

Why 3.5 inches of sag? Most people I know run between 95 to 105MM or about 4 inches. With the rear set that high it may be contributing to headshake.


This is what i was thinking. Drop the rear a bit and that should help.

  • motodude42

Posted February 22, 2005 - 08:46 AM

#24

Well, I am headshake free now. Set my sag to 4 inches and adjusted my rebound out two clicks. I am now good to go. Thanks a ton for all your help. :)

  • 5valve

Posted February 22, 2005 - 11:59 AM

#25

very helpful text (for us rookies :) )

Shock:

Setting the rebound:
1.) Find a relatively fast straight with braking bumps leading into the entrance of a corner. Reduce (Turn clicker out) the rebound damping until the rear end begins to hop or feel loose. Finally, increase (Turn clicker in) the rebound damping until the sensation goes away.
2.) Find a jump that tends to launch the motorcycle out. The rear end should absorb and then smoothly lift the motorcycle into the air. If the rear end bounces up, add rebound. (Turn clicker in)
3.) Find some large whoops. The motorcycle should track straight through the whoops with the rear wheel extending to the ground before the next impact. If it does not perform as described as above, it is packing and the rebound damping should be reduced! (Turn clicker out) (Please note the guide for sand set-up, as these rules don't apply for sand.)

Setting the compression:
1.) Find a corner with acceleration bumps on the exit. The rear of the motorcycle should follow the ground. If the rear end "breaks up", soften the compression. (Turn clicker out) (If this fails soften the rebound two clicks.) (Turn clicker out)
2.) Find some rough sections, a large jump and a couple of "G-Outs". The shock should bottom on the roughest section but it should not be a slamming sensation. Add compression to fight bottoming. (Turn clicker in.) But avoid going to far as small bump ride will be sacrificed in the trade. Remember the adjusters have a primary effect on the low speed, so even a large change in setting may only affect bottoming resistance slightly. Remember bottoming your suspension is not necessarily a bad thing. You should strive to bottom off the biggest bottoming load obstacle on the track. If you don't you're not getting maximum plushness from your suspension.


Forks:

Setting the compression:
1.) The forks should react to all track variations. If the forks seem harsh on small bumps or holes, soften the compression. (Turn clicker out) If they aren't, stiffen (Turn clicker in.) until they do feel harsh and then turn back a click or two.
2.) Now find the rough part of the track again. The forks should bottom over the worst obstacle. If harsh bottoming occurs, add oil in 5 mm increments.
Setting the rebound:
The rebound damping is responsible for the stability and the cornering characteristics of the motorcycle.
1) Find a short sweeper. When the forks compress for the turn, the speed at which the forks return is the energy that pushes your front wheel into the ground. If the forks rebound too quickly, the energy will be used up and the bike will drift wide, or wash. If the rebound is too slow, the bike will tuck under and turn too soon to the inside. Find the appropriate balance for each track.
2). With the bike turning well, the wheel should return to the ground quickly yet not deflect off berms or bounce off jumps.


Going to different tracks:

For hardpack to intermediate:
Set the compression softer, (Turn clicker out) front and rear to help get maximum wheel contact and plushness.
Sand tracks:
(Non-square edged bumps); More low speed compression and rebound are necessary. Start by adding 1-2 clicks (Turn clicker in.) of rebound and as the track gets rough, add compression 1-4 clicks. (Turn clicker in.) (Supplementary sand set-up techniques). Harshness is a result of packing in forks. Remember to add compression (Turn clicker in) to help keep the front end from packing. The rear suspension will exhibit packing by swapping. To eliminate swapping begin adding compression (Turn clicker in) until the bike tracks straight and then add rebound (Turn clicker in) to keep the rear following the terrain of each whoop. Don't be concerned if your clickers are nearly maxed out in sand conditions. Unless of course you had your bike revalved for sand.
Supercross:
(G-load, curb hits); G-loads produce slow piston speeds. This means that less dampening is produced by the shock and forks in a situation that causes more of a bottoming load. To set your bike up for Supercross adjust the compression stiffer (Turn clicker in) on the suspension (2-6), clicks and in some circumstances raise oil level and/or change to stiffer springs.


Unpleasantries?

[COLOR=Red]Headshake:
Adjust the forks lower in the triple clamps[/COLOR].
Excessive rear end kick:
Check for packing, which is identified by kick to side in hard to loam conditions. If you observe packing, soften rebound. (Turn clicker out.) This cannot be avoided if you brake improperly and lock the rear wheel up and/or pull in the clutch, on the entrance to corners.

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  • motodude42

Posted February 22, 2005 - 02:53 PM

#26

Thanks for the information 5 Valve. Very helpful.

  • jackrichmond100

Posted December 14, 2009 - 10:27 AM

#27

I agree wholeheartedly about adjusting your rear sag (with riding gear on) to the recommended sag. That is one of the FIRST things you do before you take a new bike to the track. This 3.5 shallow sag you have there is the BIGGEST contributor to your headshake. Next, since you have your compression and rebound clickers on both your forks and shock all whacked out, put them back to stock settings and give your bike a test ride. You should see a heck of an improvement. End of story really.

Now, if you feel you want to try to improve the headshake situation even more, you COULD try turning in your fork's compression clickers 2 or 3 clicks. This keeps the forks from compressing (a tiny bit) so that the forks stay up a tiny bit higher in their travel. Overall, anytime the angle of the forks are made steeper (either by the stinkbug stance caused by the shallow sag or by softening (too much) the forks' compression clickers), you are asking for that dangerous headshake.

If all all else fails, send your forks and shock to a REPUTABLE suspension company AND buy a Scotts steering damper.

  • panaman

Posted December 14, 2009 - 12:38 PM

#28

it can also be caused by the front fender catching air at high speeds, there is a reason for the short stubby SM fenders

  • Diabs

Posted December 15, 2009 - 06:47 AM

#29

[quote name='5valve']very helpful text (for us rookies :moon: )



[COLOR=Red]Headshake:
Adjust the forks lower in the triple clamps[/COLOR].
QUOTE]

This is all i did, headshake gone!.....all other info given 5valve, is awesome, thanks!

  • grayracer513

Posted December 15, 2009 - 10:36 AM

#30

Old thread. Nevertheless:

http://en.wikipedia....ki/Speed_wobble

http://en.wikipedia....l_motion_theory (scroll down to "wobble")




 
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