I've asked this question in 3 other threads and no one has even made an attempt to answering my question. But it did get me to thinking about tires and sidewall flexing.

Granted I'm not an engineer, but common sense tells me that a stabilizer must connect to the part, in this case a swing arm in order to stabilize it.. right ?

The Engine is mounted to bike frame.... tranny is mounted to engine... stabilizer is mounted to tranny and frame.

I mean, you can stabilize the engine all you want, but the rear swing arm is still floating around. Wouldn't it make more sense to design a swing arm kit that used pressed bearings instead of rubber bushings ?

And if these stabilizers make such a difference... why doesn't Harley incorporate this design in the bikes suspension... I mean I'm sure they they wouldn't intentionally produce an unsafe vehicle, right ?

With the stabilizer questions asked... What about tires ?

Tires flex side to side... the higher the air pressure, the less sidewall flex you are going to to have. Also you have to consider road surface (ruts and grooves). Now you have to factor in the weight of the bike & rider.

When you lean a bike on its side, you are going to have a certain amount of force on the downward side (gravity), then you have centrifugal force as well as G force to factor in to the equation. And lets not forget the differences in front & rear suspension effecting handling as well.

Of course the higher the speed, the more unstable the bike becomes as the variables change due to the above factors...

Wouldn't it make more sense to say that the tire flex would contribute more to the instability of a bike at hire speeds since tires can flex as much as 1/4" ???

The one common denominator that people that have expressed was high speed cornering. Of course I'm not really that smart of a person, but it would seem to me that your exceeding the tires traction capabilities when your going around a corner at 80 mph on a 1000 lb vehicle.

One more thing I have to ask those that have recently installed their stabilizers... how many of you had to add air to your tires at the time of installation..?

So again I ask, how does something attached to the transmission and the frame stabilize the swing arm ?

 

I think True-Track was the first device to address this issue.

They explain on the web site.

true-track.com

 

I'm not an engineer, either, but I attempted to answer your question on another thread. The swingarm movement is a symptom, caused my the sideways movement of the tranny changing the geometry of the bike. The braces minimize the sideways motion of the tranny, so that the curves smooth out.
There are a lot of parts that move on the motorcycle in a turn. The better the movement is controlled, the smoother the turn. Think about if a passenger shifts their weight to the high side in a curve - same thing.
We could argue all the factors forever. Doesn't matter - we have a significant number of riders here who have installed one of these braces. We don't need theory on this one. The results have been conclusive. They work, without exception. NOT A SINGLE EXCEPTION - NOBODY HAS INSTALLED ONE AND SAID "IT DIDN'T WORK".

 

Don't try so hard. Just get a stabilizer kit, bolt it on, and enjoy your "new and improved" bike. You'll be amazed at the very noticible difference it makes!

 

Not really trying to be mean here but I, for one, am not surprised that you are not in fact an engineer.
The swingarm pivot travels through the rear of the rubber mounted tranny. It can move 360 degrees. Now it doesn't move very much but it does move and this movement affects the handling of the bike in a negative way - wobble at speed. A stabilizer limits the lateral (side to side) movement of the transmission so that the rear tire follows the front more accurately thereby reducing the wobble and improving handling. Now then, this could also be reduced by solid mounting the swingarm but serious vibration would then rear it's ugly head and you wouldn't like that.
As far as tire flex is concerned you really shouldn't think that hard - you're going to hurt yourself... really.

 

I believe I found the answer that leftcoaster was dancing around that makes sense

So based on this... The engine/tranny shifts has a certain amount of movement since it is rubber mounted and The stabilizer greatly reduces the movement of the engine/tranny thus creating a more constant tension to the drive belt thus helping the swing arm stability.

If this is the case, why does everyone talk about the swing arm and the suspension when it is the engine mount that is the culprit ?

In any case, it makes sense now, but I've yet to experience this issue unless I have and never realized it.

 

I can rebuilt a semi truck from the ground up, I designed and built my house by myself...

Its all good Leftcoast... I admit I never tore apart a Harley, so somethings don't make sense until I understand the basic design.


I didn't know this... honest

Like I already said, it all makes sense now and I'm surprised as to why Harley fails to address this issue.

 

96 Ultra, in stock form there is no rear motor/trans link the pivot shaft that runs through the pivot blocks in the frame and the swingarm/trans connection is the only thing to limit the lateral movement. The stabilizer will not stop all movement, but it will reduce it considerably. The only way to stop it completely would be to solid mount the swingarm to the frame, but then you would have some teeth rattling vibrations. I also believe the problem is commonly refered to as a "wobble" but I think that is a bad description of what happens. My bike felt as if the rear wanted to take a wider line and I learned to adjust my riding style until I put the brace on that I thought worked best and wouldn't break my checkbook.