Weight balance

[Hubcap]

Norfolk's bike's developed a nice front end wobble when he lets go of the handlebars.

What's the possibility of the lack of exhaust upsetting the balance of the bike?

His tyres are still the same and he said it only seems to have happened since the exhaust came off..

what's the chances?

thanks all!

[Buzzin (^_^)]

I'de say unlikely (but I could be horribly wrong here)
Mine developed the same problem....but I'm putting it down to tyre wear/unbalance.
Perhaps one of the wheelrim weights came off? (you know...the weights they balance the tyre/wheel with?)

[McF]

I agree with Buzzin, it's very unlikely

There isn't much weight in the silencer, a lot less than a passenger, and generally less than many people would carry in a top box, panniers or a daysack strapped to the seat.
The silencer is only clamped on at two sites that I can recall - where it joins the collector box and on the right hand hanger, it doesn't offer anything for stability etc.

Front end wobble is more likely to be caused by:
Wheel bearings failed
steering head bearings - loose, or "set" (do they feel like a "notch" when pointing straight ahead?
Rear Suspension failing
Tyres badly balanced (as per Buzzin's suggestion)
Wheels buckled

[skyhook]

Jul 7, 2009 11:06:28 GMT 1 Hubcap said:

Norfolk's bike's developed a nice front end wobble when he lets go of the handlebars.

What's the possibility of the lack of exhaust upsetting the balance of the bike?

His tyres are still the same and he said it only seems to have happened since the exhaust came off..

what's the chances?

thanks all!

He lets go of handelbars ? Not a good idear.........lol

[Hubcap]

Thanks for that guys, he did notice that his head bearings had loosened a little, but he tightened those up, it's possible they've set now.

I doubt it's his tyres because they've not changed since well before it started it, and I don't recall the tyres having balance weights in the first place, although that was the problem when my handlebars wobbled, minessorted now.

I'll let him know to check that out

[De Graaf van Salland]

On one of my advanced riding courses the instructor had a film about unbalanced bikes. This is quite a few years back and I'm trying to remember as much as possible; details have been lost during the years. But here it is:

There are two versions of unbalance in a motorbike:

There is the "low speed wobble". This is rather harmless & happens in most bikes when you let go of the handlebars at a specific (but rather low) speed. (My bike does it).
Every mechanical system has it's own frequency. When riding, the tyres will introduce a certain frequency of vibration into the bike.
If the two frequencies happen to be the same, the wobble will start.
Normally when you have your hands on the handlebars, this is enough dampening to stop the wobble before you even start to feel it.

And there is the more dangerous "high speed jimmy".
I tried google-ing this name, but it didn't come up with anything. So I'm not sure the name is correct.
If you do not do anything about this, the bike will throw you off eventually.
I don't know the cause of this one, but I do remember the remedy: move your weight forwards. Just bend as far as possible over the handlebars; put all of your weight on the front wheel and the vibration will stop. (Don't brake at this point !)

Apparently this high speed jimmy is quite a frightening experience. There are stories of experienced bikers who stopped riding motorbike because of such an experience.
Fortunately, I've never experienced one myself, but I do keep the remedy in the back of my mind just in case...........

Franklin

[Buzzin (^_^)]

The correct term for that would be a tank slapper (or rather, that's what it ends in if you don't stop it)
And yes....that can scare you off your bike.
Here's an example:


The lower speed wobbles however are annoying when like me you want to be able to take your hands of the bars once in a while....

[skyhook]

Jul 8, 2009 8:11:29 GMT 1 De Graaf van Salland said:

On one of my advanced riding courses the instructor had a film about unbalanced bikes. This is quite a few years back and I'm trying to remember as much as possible; details have been lost during the years. But here it is:

There are two versions of unbalance in a motorbike:

There is the "low speed wobble". This is rather harmless & happens in most bikes when you let go of the handlebars at a specific (but rather low) speed. (My bike does it).
Every mechanical system has it's own frequency. When riding, the tyres will introduce a certain frequency of vibration into the bike.
If the two frequencies happen to be the same, the wobble will start.
Normally when you have your hands on the handlebars, this is enough dampening to stop the wobble before you even start to feel it.

And there is the more dangerous "high speed jimmy".
I tried google-ing this name, but it didn't come up with anything. So I'm not sure the name is correct.
If you do not do anything about this, the bike will throw you off eventually.
I don't know the cause of this one, but I do remember the remedy: move your weight forwards. Just bend as far as possible over the handlebars; put all of your weight on the front wheel and the vibration will stop. (Don't brake at this point !)

Apparently this high speed jimmy is quite a frightening experience. There are stories of experienced bikers who stopped riding motorbike because of such an experience.
Fortunately, I've never experienced one myself, but I do keep the remedy in the back of my mind just in case...........

Franklin

Not sure if this is the way to recover from a tank slapper But he did put all he's weight on the front : But overkill for me, I am not that supple at my age.......lol

[McF]

Buzzin beat me to it - "Tank Slapper", because that's what happens. I had one once, felt as bad as the video posted by Buzzin shows - wosrt thing you can do is brake or decelerate. Weight forward helps, so does a touch of throttle (it's counter intuitive, but you are most stable when accelerating (unless you crack it open so far the front wheel is pointing heavenwards!)).
It helped me that day.

As for the aerobatics in Skyhook's video - wow, a desperate guy indeed, imagine what is grip on the bars must have been like, I hope his cheeks were clamped together as tightly!

I keep meaning to post more about counter steering. I've been trying to do this consciously for several weeks and do notice quite a difference.
When I have a little more time, I'll dig out the old thread and post.

[McF]

Jul 8, 2009 8:11:29 GMT 1 De Graaf van Salland said:

And there is the more dangerous "high speed jimmy".
I tried google-ing this name, but it didn't come up with anything.

Try "High Speed Shimmy"

I rode home last night, over 300 miles on the mighty Pan, so a lot of thinking time.
At one point with a fierce crosswind, poor road surface and I suspect my steering head bearings are nearing the end of their life - I got a bit of a wobble which had me thinking "what expression could you have been thinking of" a few miles later "shimmy" popped up.

As per my earlier post, a little acceleration, small increase of weight on the bars and we were fine. With some clear roads later, I tried recreating the conditions for a wobble, even setting cruise control and taking both hands away from the bars. Like a cruise missile, we kept on course. Tried the same without cruise control, so that speed was decaying (a lot less stable condition) and I found one spot at about 65 where the bars give a little shake then corrected themselves before I could do anything.
Do not try this at home!
My point is: a wobble can get anyone, often from a random coincidence of conditions, but always when you least expect it. Stay in tune with your bike (which really means, get out and ride it as often as you can ;D) and have a plan for "what if" something happens - then hope that you never have to use it!
As we say at work - Plan for the worst and then hope for the best!

To quote Jaz - "Ride Safe"

[De Graaf van Salland]

Hi McF,

Thanks for finding the right name for it ! ;D

Franklin

PS. due to a holiday I won't be on this forum as often as normally, for the coming 3 weeks.