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Handlebar wobble accelerating

3380 Views 6 Replies 6 Participants Last post by  Skelee
So I've had a few bikes, one sportsbike and 2 cruisers.

This is the only bike Ive had that wobbles the bars sometimes when accelerating hard through 2nd, 3rd and 4th. So far it's just been that - I relax my grip and it goes away.

Is it me, or is it my bike?
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It's your bike! But, to reassure you, it's the same with all of them.....there is a rubber mount in the bar clamp fixings which causes this movement. It can be unnerving until you realise that it's supposed to happen!
nah, its not just the flex in the bar mounts, i know about that.

it's front wheel shimmy.

to be fair, think I've answered my own question - its only when the front wheel is skimming the surface on hard acceleration - leading to wheel shimmy. I had the feeling yesterday that if I held on any tighter, it would have developed into a tank slapper.

I think I've only came across it recently since I'm now really comfortable with the bike and in this good weather, I'm starting to push it towards the edge a bit more in cornering and acceleration.

my question, then, is: does anyone else find this?
I definitely noticed that this front end is prone to wobble much easier than on my previous bikes. However riding home from work this morning, after my most recent addition of the sw motech crash bars, I found that they greatly reduced the bikes inclination to wobble. In fact it seems now that it would require enough input to get the front to shimmy that it would be dangerous to do so. So apparently a small change to the weight distribution of the bike has had very beneficial results.
Had a big wobble when accelerating hard up to 90+mph (just overtaking, officer) which was scary. Think it may have been compounded by the little screen I have.
Could be due to tire wear too, I would venture to guess that the Pirelli tread has potential to develop tread cupping that can cause the wobble described. If you run your hand over your tire, front to back you will likely feel the trailing edge is raised and the alternating block design will cause a vibration that will become a wobble if not holding the bars (coast down hands off) and can be felt if the cup is large enough. We had some Gold Wing riders report that wobble in as few as 500 miles. It was always if they took their hands off the bars though and even the lightest of touch on the bars would stop the wobble.

It happens because the rotational forces on the front tire are uni-directional. The braking as well as the normal rotation resistance due to friction are only one way. The back tire has a different type of cupping, being side to side due to the direction of forces from cornering. The forces of acceleration and deceleration/braking work opposite directions so this fore aft cupping doesn't happen on the back.

Here's an extreme example of the extreme wear on a front tire:


I haven't experienced any vibration with my bike and I have raised the forks in the triple clamps 10mm and may go to 20mm, to quicken turn in. That would ordinarily increase possibility of wobble, but I have no problem. I like my bikes to have quick handling. I will have to wait and see when the tires wear enough to cause the feeling.
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no wobble for me, vibrations at 120pkh or more
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