Wobble At High Speeds

[AnikMankar]

During one of my rides to Manas (about 120+ kms from Mumbai) - the bike picked up a major wobble at high speed... was not sure what caused it – wind, bad tyre(s), suspension, bearings ???

Confidence level drops while riding if the bike tries to control you instead the other way around, body goes stiff basically you stop enjoying the ride.

Couple of theories ...(i read... don’t quote me on this part !!)

“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. Bike will go through various "zones" of oscillatory stability and instability as it accelerates up to its highest speed. “

My thoughts...

Tyres : The bad tires is a contributing factor, particularly the front one as different treads have different resonant properties – mine are relatively brand (Metzlers) new so i did rule it out.

Wheel balancing : Well balanced wheels increases road holding and reduces tire wear and rider fatigue – unfortunately no one locally does this so i am assuming mine are not!

Forks and Steering : Lack of Fork oil and too much side play in the swing arm are sources of vibration. Worn steering head bearings can cause wobble too. Mine are recently shifted to cone type bearing – they have helped in my overall handling of the bike.

Wind : The wind wash from driving near a truck can also cause a steering wobble – we had clear roads so not wind wash. However it was blowing quite a bit, i waited for the wind to die down as i feel that initiated the wobble in the first place.

Dampeners : Steering dampers are there on the newer bikes (after marker ones are also available ) to help with this problem to some extent.

The problem may go away with more speed but the best way to take the bike out of that is to back off. All I did was slowed down to a point where the wobbling stopped and then moved on. I completely forgot that I have a steering damper and was on medium setting. On the way back made the damper tighter which took the wobbling away – this did counter the wobbling but not sure if i solved the root cause. Need to check the rear suspension.

Ride Safe !!

[Bassie]

Bearings worn out? I had this with a Porsche once, the bearing in the back wheel was gone and it started to "dance" all over the place when running at high speeds.

And yes it does feel like your going to crash any second soon.

[Mohawk]

You don't say what kind of wobble. A normal speed wobble gets the bars wagging back & forth & it can get worse as speed increases, but can also sometimes be ridden through, or eased by relaxing your grip on the bars. If the bike has done this speed without the wobble previously, has anything changed ? Tyres, suspension settings, loading on the bike, passenger, luggage etc !? If not then it will be wear related, assuming you have used the same road before without incident.

First check your tyres for damage or excessive wear. Also check pressures, as they can have a major influence on stability !

Then check your wheel/axle bearings.

Then check your head bearings, they are an adjustable part. If they are ball bearings the adjustment is very small, if they are tapered bearings there is more room for wear & adjustment.

It is usually one of these that cause wobbles on a bike that was fine before !

[wera803]

My bike used to wobble at speed, especially going around semi's. It was worse with the trunk on it. I think it was all suspension settings. Pre-load cranked all the way up, the valving not set up for my weight, etc.

[AnikMankar]

You don't say what kind of wobble. A normal speed wobble gets the bars wagging back & forth & it can get worse as speed increases, but can also sometimes be ridden through, or eased by relaxing your grip on the bars. If the bike has done this speed without the wobble previously, has anything changed ? Tyres, suspension settings, loading on the bike, passenger, luggage etc !? If not then it will be wear related, assuming you have used the same road before without incident.

First check your tyres for damage or excessive wear. Also check pressures, as they can have a major influence on stability !

Then check your wheel/axle bearings.

Then check your head bearings, they are an adjustable part. If they are ball bearings the adjustment is very small, if they are tapered bearings there is more room for wear & adjustment.

It is usually one of these that cause wobbles on a bike that was fine before !

I was doing about 90miles, when the wobble started. Felt like the back wheel was sliding off in a straight line...difficult to explain -but scared the shit out of me.

My head and front wheel bearing are recently installed about 800 miles ago. Tyres too are brand new...all the threads are intact.

I am suspecting the rear bearings or the rear suspension. Tightning the damper the wobble went away. Maybe need to recheck the head bearing slack.

[2thdr]

If you haven't checked your bearing tightness since your recent installation, I would say that is the most likely culprit. I think there is a procedure for installing tapered roller bearings that involves tightening to torque (or your in-your-hand torque meter), backing off and then re-tightening. Someone with more knowledge will correct me. I am doing this job this weekend with huntinggunns, so I will be an expert in a few days! LOL.