Why do you get the wobble?

[Snake Ranch]

Why do you get Motorcycle speed wobbles?


Answer by Gregg Anderton
Confidence votes 24.5K
I am a Mechanic/ Equipment Manager,/Drag Racer/Classic Car Restorer/Jeep Owner


High speed wobbleSpeed 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.

[MET-RICK]

Thanks Snake Ranch, interesting article. I 'sometimes' but not always do get a wobble/shimmy (tail wagging the dog ) type action when cornering fast and/ or aggressively...sometimes it seems to happen out of the blue while holding my line, other times it can happen when making an adjustment on my line. I just subtly get out of the throttle a bit, keep the arms and shoulders relaxed and she smooths back out. I'll try out the test procedure next time out. Cheers.

[matj1990]

Originally Posted by MET-RICK

Thanks Snake Ranch, interesting article. I 'sometimes' but not always do get a wobble/shimmy (tail wagging the dog ) type action when cornering fast and/ or aggressively...sometimes it seems to happen out of the blue while holding my line, other times it can happen when making an adjustment on my line. I just subtly get out of the throttle a bit, keep the arms and shoulders relaxed and she smooths back out. I'll try out the test procedure next time out. Cheers.

I get this same problem when cornering at high speeds 80mph 75mph or so i get a wavy dog tail wag ... 9 bikes this is the first time I have encountered this and I only have 9k on it

[recumbentbob]

Originally Posted by matj1990

I get this same problem when cornering at high speeds 80mph 75mph or so i get a wavy dog tail wag ... 9 bikes this is the first time I have encountered this and I only have 9k on it

Try 40psi front & REAR IN Tires and stiffen up the rear shocks.
See if that helps.

[skiman]

[MET-RICK]

Wow lots of possibilities and things to check, thx. The guys I ride with told me to start with the steering nut....the one in the leathers sitting in the seat . Geesh... tough crowd I ride with, as Rodney Dangerfield would say, "I just cant get no respect". . Cheers.

[Dieago62]

I can tell you this I have 17000 on my bike 11000 when I bought it.
the pin bolt on swing arm was worn very bad where needle bearings run. the top bushing in fork tube was badly worn and steering bearings were not worn out but loose. All changed and drives like new again other than the Michelin C2 rear tire slips and drives funny until hot with only 6000 miles on it. it is cupped where the two outer tread groves meet. upon changing swing arm bearings and pin/bolt I drilled tapped and installed grease zurk so no I can grease it with grease gun

[MET-RICK]

Originally Posted by Dieago62

I can tell you this I have 17000 on my bike 11000 when I bought it.
the pin bolt on swing arm was worn very bad where needle bearings run. the top bushing in fork tube was badly worn and steering bearings were not worn out but loose. All changed and drives like new again other than the Michelin C2 rear tire slips and drives funny until hot with only 6000 miles on it. it is cupped where the two outer tread groves meet. upon changing swing arm bearings and pin/bolt I drilled tapped and installed grease zurk so no I can grease it with grease gun

Gotta love it when a plan comes together. I think I sense a winter project coming on. Nice touch with the addition of the handy dandy grease piece install ...(going bez-zurk ). Cheers