strokerlmt
Moderator
Correct me..I'm no expert.....but don't most wobbles originate from the forks ???
LMT
LMT
A wobble is a harmonic based upon the resonant frequency of the bike...the whole bike...not just the forks. Wind can induce it...but only one element. Higher angular velocity of the wheels at higher speed and wheels and tires that are out of round or out of balance in combination of the wind can cause it.Correct me..I'm no expert.....but don't most wobbles originate from the forks ???
LMT
A wobble is a harmonic based upon the resonant frequency of the bike...the whole bike...not just the forks. Wind can induce it...but only one element. Higher angular velocity of the wheels at higher speed and wheels and tires that are out of round or out of balance in combination of the wind can cause it.
I have had my bonnie over 100 mph on ocassion with no windscreen and never had a single wobble. The bike has to be right to not wobble at high speed and that means everything I mentioned earlier and also the comment about rear wheel alignment. People tend to think of things in binary terms for convenience. Most issues aren't that easy. Generally a wobble is created due to an interaction of things out of spec. If the forks are too tight or loose for example with a slightly out of balance wheels with borderline tire pressure...can cause it. A motorcycle is one giant spring with resonant frequency...from tires to spokes to fork deflection to the frame flex etc. If the inputs like wind and road surface and rider weight etc match this frequency, it will oscillate. All things have to be looked at if this is as problem...even tire wear affect and specific tire tread pattern relative to road surface can cause it. Its a problem in fact with many motorcycles and just changing a single variable like tires from one brand to the next can either solve it or cause it. Even a death grip on the handlebars can cause it some instances because it changes the overall stiffness of the bike.
Thanks Bullitt.Great explanation George! :headbang2:
The bike has to be right to not wobble at high speed and that means everything I mentioned earlier and also the comment about rear wheel alignment.
With Bonnies you can have everything right and it'll still wobble, it seems some do and some don't. As has been said, rear wheel alignment is very important. You can't trust the alignment marks, so I made a tool to get the wheel spindle exactly the same distance from the swinging arm spindle on both sides. My alignment marks were a couple of mm out.
Oxymoron. Case in point mine and others don't wobble...ever. You mentioned yours does at times. I do agree its a lottery aka tolerance stack up...but submit to you something is out of spec. If you haven't tried every permutation then you haven't exhausted all root causes.With Bonnies you can have everything right and it'll still wobble, it seems some do and some don't. As has been said, rear wheel alignment is very important. You can't trust the alignment marks, so I made a tool to get the wheel spindle exactly the same distance from the swinging arm spindle on both sides. My alignment marks were a couple of mm out.
Lasering the chain will only burn microscopic holes in it and weaken it.I have also tried the laser up the chain, it was not as accurate as getting the swinging arm and wheel spindle measurement the same both sides.
I have also tried the laser up the chain, it was not as accurate as getting the swinging arm and wheel spindle measurement the same both sides.
----------- ____________
Built the frame meself.
If you have checked the setup of the bike and it is all correct and it still wobbles over 85mph, then you'll have to adapt your riding style and position.
I have had this problem for the last three years and after changing to cartridge forks, 17" cast wheels, upmarket rear shocks, steering damper and changing all bearings in the wheels and steering, it is still there above 85mph. (a steering damper won't stop this, it just limits it a little)
The cause of my problem is Hyde Western bars and 28mm risers, but for 80% of my riding they are a great setup and very comfortable. The more upright your riding position and the more you go over 85mph, the more violent the wobble. It seams the wind blast acting on your body lifts the front end and causes the wobble.
The only cure to the problem I have found, is to take the pressure of the wind blast on your torso, in your stomach muscles and put no rearward force on the bars, just hold them firmly. With this riding style I can go up to around 115mph and if I lay on the tank over 120mph with no wobble.
Give it a go next time you're heading to the ton and see if it cures your problem.
I have the 17 inch from alloy wheel. I always check tire pressure. I have a fork brace, steering damper and I have played with the internals on the forks. I have seen 100 on numerous occasions with and without my saddle bags. I have to be honest that is not the norm for me. But 70-80 on the highway loaded happens a lot. I have never had a wobble. Having said that I don't know which bit would be the best.
LMT
Agro, I did the CBR600 F3 conversion, forks and wheels.