front wheel wobble when hands-free

[cowbean]

I managed to drop my bike in the dirt today, while turning around in a turn-off. dropped on ride side; other than fairing rash, no obvious damage. (and no damage to myself either, other than a slight bruise on my leg where the bike ended up sitting.)

however, i notice that when i'm cruising in a straight line, and take my hands of the handlebars, the wheel / bars wobble slightly.. and then stop wobbling.

it could be that this existed prior to my dirt dumpage, as i bought the bike used and it had been down on both sides already, albeit from what looks like completely stopped, driveway drops (judging from existing scratches on the fairing).

it doesn't look like any part of the front wheel / suspension hit the dirt at all. but maybe the sidewall of the tire... possibly denting the rim?

could this be a serious problem? if it's something a mechanic should take a look at... can anyone recommend a mechanic?

 

[imurdaddy415]

why do you take your hands off the bars... I mean do you want to crash?

 

[Stormdragon]

The wheel could be out of balance. I'd check that first since that's cheapest/easiest. I'd look at steering head bearing tightness as well. It could be a notched set of bearings, but unless you're stunting the bike, I'd doubt it on such a new machine.

 

[cowbean]

why do you take your hands off the bars... I mean do you want to crash?

no, i am not overly fond of crashing. but i was concerned that the drop could have thrown something out of alignment, so by way of checking, i took my hands off during a straight section of 35, thus discovery this issue.

i probably would never have noticed this otherwise; can't feel any oscillation in the bars with my hands on them... so therefore not sure if it was my drop that did this, or a pre-existing condition

The wheel could be out of balance. I'd check that first since that's cheapest/easiest. I'd look at steering head bearing tightness as well. It could be a notched set of bearings, but unless you're stunting the bike, I'd doubt it on such a new machine.

thanks for the advice! will check wheel balance.

 

[cowbean]

Having seen the triple-trees on the new 650r's I'm willing to bet if you fell over and smacked a bar end into the ground you've tweaked your fork tubes in your triple-trees causing a misalignment.

Nothing is bent, just tweaked. Imagine holding the bottom triple tree and the top triple tree in your hands and twisting them opposite directions slightly and what that would do to the alignment of the fork tubes/axle.

If I'm right and you did hit a bar-end on the ground when you fell over, the fix is easy. get the bike in the air, take off the front wheel, loosen all the bolts and top nut on the triple trees, slide the fork legs down and back in to place, and cinch everything back up. That usually takes care of it.

this is possible. i did notice some dirt on the right bar-end when i picked it up, *and* that bar end had a scratch on it already from the previous owner's drop.

while the procedure sounds easy enough, i am not at all equipped to do it. is this the kind of thing that should be taken care of immediately? is there potential for immediate risk or long-term damage?

 

[cowbean]

So had you ever taken your hands off the bars prior to the tipover to see if you had any headshake while coasting?

nope, not on this bike... and no detectable trace of headshake with either one or both hands on the bars. the shaking seems to start a second or two after my hands come off.

 

[Karbon]

whne you took your hands of the bars were you decelerating correct?

at what speed were you going when you did this?

uphill downhill or flat?

what was the pavement surface like?

was this phenomenon repeatable?

 

[cowbean]

whne you took your hands of the bars were you decelerating correct?

at what speed were you going when you did this?

uphill downhill or flat?

what was the pavement surface like?

was this phenomenon repeatable?

Yes, decelerating from engine braking, starting at around 40 mph. this was on the straight sections of 35 between 9 and 84, i believe the terrain was mostly flat, maybe slightly downhill. pavement surface decently smooth, not newly paved but not pitted either, no gravel.

 

[arnoha]

I had this issue on my FZ-6. It can be caused by many things. In my case, the seal on the lower head bearing had failed. I never did find out why it failed; the reason wasn't obvious. It may have had to do with falls, as I've had a couple like the OP. However, the failed seal allowed dirt and water in and that rusted the ball bearing. I replaced the ball bearings with roller bearings and never looked back. Fixed the problem.

Dunno if this helps; it's just my experience.

 

[ST Guy]

The "dreaded" hands-off-the-bars deaccelleration wobble is really not all that uncommon. And it's more common on modern machines with steeper steering angles. The front tire is always trying to align itself with the direction the bike is going in. But it often over corrects and then corrects again, etc. Most of the time you don't see or feel this. But other times, like when you take your hands off the bars, it becomes noticeable. (This action is much like the grocery cart wheel that wobbles. If goes from side to side, overcorrecting each time. If you were to damp the steering axis that the grocery cart wheel 'steers' about, you'd stop the occilating. Or, if you put tiny handlebars on the wheel and had a miniature monkey grab the bars, you'd damp out the occilations also.) What you are doing when you take your hands off the bars is removing a damping force (your hands and arms) and the bike is also deaccellerating which loads the front tire more. Both these things contribute to that wobble. Another contibuting factor is the width of your contact patch. Worn tires will cause this more than new tires, for instance. There are many other factors as well but I won't go into them here.

First thing I'd do is make sure that everything is in proper alignment and that nothing is tweaked. Then make sure air pressures are good and that the forks are working properly, i.e., the bushings are not worn, and the damping is working as it should. Also make sure that the steering stem bearings are in good shape and properly adjusted. Same for the swing arm. Also check wheel bearings. Then take the bike out for a test ride. Don't be surprised if the wobble is still there.

You can either:

Ignore it and keep your hands on the bars, knowing that there's nothing really wrong because you've checked everything out.

Or you could install a steering damper.

Or the cheapest way (and I've never heard of this not 'curing' the problem) is to install tapered roller bearings at both ends of the steering stem. It seems that just the slight added drag of tapered roller bearings over ball bearings makes a world of difference. This deaccelleration wobble is a known "issue" with ST1100's (and new Wings for that matter), and installing tapered roller bearings takes care of the problem.

I suggest CBR Bearings.

Oh, and generally speaking, radials will exhibit less of the wobble tendency than bias ply. That's because the sidewalls are more compliant and damp out the occilations better.

 

[Sidewalk]

All of my bikes sportier have done. Even my brand new (at the time) 1000RR would do that. Of course that was also in gear so there was more weight shift, I have never done it in neutral.

 

[cowbean]

thanks for the very helpful replies guys. i will probably get it checked out by a mechanic, with the above-mentioned guidelines, to be sure.

 

[cowbean]

I rode around running errands today, and i actually couldn't reproduce the headshake very reliably. I tried maybe 10 times, and most of the time the bars held steady. A couple of times there was a brief shake, and then they settled down. Only one time was there a prolonged shake that looked like it might continue if I let it.

Perhaps road conditions have something to do with this? Also it seems to happen at a specific speed (~40 indicated), nothing below or above.

Given that this doesn't seem like a persistent, serious issue, I may wait till my 4k maintenance to ask a mechanic to take a look.

 

[Bronto]

Read posts about this minor head shake. It's all the above posted. Each time it was narrowed down to a tire unbalance, head bearing, tweaked forks and more. But because it was a crash, as Moike says tweaked forks one likely cause. The procedure described by riders to untweak forks.
Loosen the upper triple fork pinch bolts. Loosen the axle pinch bolts, both sides. Leave the middle lower triple pinch bolts alone, kept tightened.
Get on the bike and push the front wheel into a wall. Without using the brakes, just front wheel pushed into the wall. Bounce up/down on the seat and bar grips several times.
Carefully back away from the wall a few inches. Before getting off the bike tighten the upper triple pinch bolts.
Get off the bike carefully and lightly set on kickstand. Tighten the axle pinch bolts.

 

[ST Guy]

But, honest fact is.... Every motorcycle from the factory should ride hands off coasting down in netural with no headshake with the damper backed all the way off.

True, we'd like to have all motorcycles come from the factory and not exhibit this tendency at all. But the fact is, some or even many do. And no amount of fine tuning of the stock components will take care of the problem. It was a known problem on Honda's ST1100. Radials helped. Some aftermarket suspension tuning helped. But what really did the trick was getting rid of the ball bearings in the steering stem and going with tapered rollers.

I've also followed somewhat the same problems riders are having with newer wings. Same symptom, no amount of fine tuning of the stock suspension, tire pressures, loading of the bike, etc. will help. Honda says it just does that. But a swap to tapered roller bearings in the steering stem takes care of it.

'Be nice to have all bikes perfect from the factory. But they aren't. Oh well. 'Gives us something to do, I suppose.