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Need for Speed

Why do you get Motorcycle speed wobbles?


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2012-03-27 14:17:59
2012-03-27 14:17:59

High speed wobble

Speed wobbles can occur whenever something starts a vibration that matches a resonant frequency of the wheels. A resonant frequency is one at which your motorcycle will vibrate very easily; a particular motorcycle may have multiple resonant frequencies. The starting point may be a bump in the road, a rough patch in the road, or some combination of these factors. Other potential contributing factors include the small torques resulting from wheel rotation and the tiny lateral oscillations that spinning wheels make if they're not aligned with absolute perfection.

Your motorcycle will go through various "zones" of oscillatory stability and instability as it accelerates up to its highest speed. you might even compare this to musical notes or octaves of relative vibrational resonance.

Steering dampners are made to help with this problem as the main dampner ( you ) cannot always handle the correction of the vibrations.

The best advise is to slow down, as this can be a fatal but also unavoidable occurrence and even though the problem may go away with more speed the best way to take the bike out of that particular resonance range is to back off.

The tread of your tires could also be a contributing factor, particularly the front one. different treads have different resonant properties.

In addition to above, get both wheels statically and dynamically balanced. It reduces wobble, increases road holding and reduces tire wear and rider fatigue. Check forks and swing arm for correct operation. A lack of fork oil and too much side play in the swing arm are sources of vibration. Check panier box lids are fitting properly and are locked. Lid 'chatter' in the wind can be one of those resonances mentioned above that sets wobble off.

If your motorcycle is pulling a sidecar or has a handlebar-mounted fairing, this will increase the likelihood of a steering wobble under certain conditions. The wind wash from driving near a semi truck can also cause a steering wobble.

Although many things can contribute to starting a wobble, they generally won't happen if your steering head bearings are properly maintained. Test your steering head bearings by accelerating to 50 mph or so on a straight, smooth road on a calm day with no oncoming traffic. Close the throttle and remove your hands from the handlebars. If your bike's steering seems to pick a direction and stick there, your steering head bearings are too tight. If there is any wobble at all, your steering head bearings are too loose.


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