Originally Posted by FinalShot

And, I'll add rider position.

I can introduce wobble by trying to fight the lean while in a turn. When I was learning how to race dirt bikes many years ago, this was one of my problems. Even on dirt bikes, if you did not stay in line with the bike you could start a wobble.

I've see this with new riders as well. Go in to a good sweeper and the rider leans only "half" with the bike. Almost always, especially if the road has a bump, the rider will report a wobble feeling. Get them to lean more and the problem goes away.

Originally Posted by grbrown

After proof reading the darned thing!!!!

Originally Posted by davessworks

Oh lighten up for heavens sake. I've (almost) always enjoyed reading your contributions to this board. You've let yourself down within this thread.

Originally Posted by LoneGrey

post removed -- even though original, not plagiarized, it was no value added

Originally Posted by TKDKurt

You're never going to last on the forum if your feelings are so easily hurt. Stand up for yourself, don't just take your ball and go home.

Originally Posted by LoneGrey

The Original post was removed because although original and none of which was plagiarized, it apparently didn't seem to offer much value. I rarely post. I post only when I think I have something of value to offer. I never post or comment for the sake of adding up post counts or just to be heard. However, despite the thousands of posts on this subject, I do believe I have information based on sound research and technical analysis and is worth sharing. UPDATED POST:

INTRO: It is not my intent to challenge others experience or knowledge, nor diminish the many years of posts on this subject, nor duplicate them. And it is most certainly not my intent to supersede a most excellent “Bagger Wobble Exposed” post by GRBROWN,UK, https://www.hdforums.com/forum/tourin...e-exposed.html, July2012. This post is an attempt to get this 200+ year old subject into one box and explain it from a summary level physics/engineering perspective and, most importantly, list the fixes that actually work.

TECH DESCRIPTION: The wobble is a sustained oscillation felt primarily in the front end. The conditions needed for sustained oscillation are (in a nutshell, thus avoiding a lengthy, detailed physics & engineering explanation): underdamping, multiple stored energy sources, and a mode of energy transference between these sources (a feedback loop). You cannot eliminate the sources of stored energy, which are the spinning front and rear wheels (essentially two large gyroscopes), and the bike/rider system (mass, velocity, and gravity). You cannot eliminate the feedback loop. The front and rear wheels, engine and trans, front forks and rear shocks, all need to be somehow connected—answer, the frame, which by the way needs to be as rigid as possible or it too will be a source that allows the system to oscillate. That leaves underdamping. One must eliminate or minimize all sources of underdamping, and for us, there are many sources. But first, in the context of this subject, let’s be clear on what damping is.

DAMPING DEFINTION: Within the vehicle engineering community, from motorcycles to planes, trains, and automobiles, even space vehicles, damping refers to anything designed to be in motion but also has attributes designed to dissipate or isolate energy stored in oscillations that could occur from it being motion; i.e., damping prevents it from wiggling, wobbling, swaying, fluctuating, swinging, undulating, or most simply, moving in a plane it is not suppose to move within. Now, back to eliminating underdamping.

THE FIX: You cannot completely eliminate 100% of all underdamped sources, but you can minimize them and fix the wobble, oscillation problem. Some required one fix, others (like me) had to do several (I have a 99 FLTR; my brother has an 04 FLTRI, all stock, and rides likes it’s on rails).

[*]Increased tire pressure from 36 or lower to 38 or 40 psi (most common) [*]Tightened steering head bearing to spec (very common) [*]Loosened steering head bearing to spec (somewhat common) [*]Replaced steering head bearings (not common) [*]Replaced front wheel bearings (not common) [*]Re-aligned rear wheel after new rear tire installation (common) [*]Tightened loose spokes on laced wheel (not common) [*]Aligned Vehicle (very common): Adjusted belt tension, then adjusted rear wheel axle to swing arms shaft distance (left and right sides must be exactly the same), then aligned vehicle. The goal is to get the real wheel in plane with the front wheel. I use a pair of 8’ fluorescent tubes, bungee corded to the rear wheel. Line up the front wheel parallel and centered within the two fluorescent tubes. Measure the gap between the tubes and edge of front tire at four points (assumes your rear tire is wider than your front; if they are the same width, you should have equal contact at all four points). You want the four gaps to be equal or as near equal as possible. When measuring the gap between the tubes and edges of front tire, the gap can change by as much as 5 mm (~ 3/16 in) with a mere 1/2 turn on the lower engine stabilizer link; so it shouldn’t take much to get your rear wheel lined up with your front wheel (there are exceptions – like my bike—that’s another story). [*]Replaced front motor mount –worn out mount allowed rear wheel steer (common for bikes with over 60K miles; recommend you check swing arms rubber bushings/isolators, too) [*]Stabilized the rear fork / swing arm to eliminate lateral swing arm movement (this is the biggy – it’s a weak design point not only for HD, but others as well):
[*]Replaced swing arm bushings/isolators with new ones $50 (common for bikes with over 60K miles; would be wise to replace the front motor mount, too) [*]Installed swing arm/engine/trans stabilizer kit. There’s about ten different manufacturer choices ranging from $100-$400. Not all bikes need this, including baggers, but many have done it, including me. I would make this my last resort.
[*]Replaced front and rear tires with manufacturer approved set (do not mix bias ply and radials; do not put radials on a bike that was not designed for radials—huge mistake!) [*]Flushed and serviced front forks. Fork oil level in left was not same as right (mismatched damping -- not common) [*]Replaced front forks or rear shocks (left/right side damping not equal -- this is rare)

THINGS THAT ARE NOTTHE PRIMARY SOURCE OF A WOBBLE

1. Vehicle (wheel) alignment is not an underdamped source. It’s a cyclic stress source. The misalignment creates lateral forces that acton the swing arm and rear tire (neither of which are perfectly rigid-- both have damping issues). As the frequency, which increases with speed, approaches the natural frequency of your steering/suspension system, the wobble begins. These small lateral forces can produce very large oscillations within seconds and can progress from mild to violent, uncontrollable gyrations that have taken riders down.

2. Wheels out of balance - this causes vibration and can trigger a wobble but is not the source; it’s a stimulus, similar to a bump in the road that starts the oscillations but is not what’s allowing the wobble to occur.

3. Rider position on the bike - this affects CG and thus stability, but is not a cause. It’s just another stimulus like a grove in the road that puts stress on the steering/suspension system.

4. Overloaded luggage, or one bag much heavier than bag on opposite side – like rider position on the bike, these affect CG and thus stability, and also stress the steering/suspension system.

5. Windshields and fairings – these are special case items unrelated to mechanical damping but can (rarely) create a wobble from an aerodynamics perspective. Exception – avoid cruising down the interstate in the wake of a semi that’s generating wind vortices at 70+mph.

[*]Rake or castor - changing the original design of the bike using after-market parts affects CG, turning radius, and stability, but is not a cause provided the new parts do not move in planes they are not suppose to move in; e.g., the forks do not flex or twist or move laterally.

ROAD TESTS

[*]Stability: On a straight, flat road where there’s no traffic and plenty of room, momentarily ride hands free at 40, 50, 60, and above. The bike should track straight and not drift left or right, and there should be no evidence of wobble, wiggle or front end oscillation.

· If the bike drifts left or right, the clutch cable may be pushing on the forks, weight balance may off, the alignment may be off, or your steering head bearings may be too tight. Correct these and try again.

· If the front end shows signs of oscillating, you have more fixes to do.



[*]The Sweeper. After you get the bike to track straight and there’s no evidence of front end wanting to oscillate, find a long, wide sweeping curve that you have to really push the lean factor to execute at 60+. Would be better, safer if the curve has two lanes, one way. Take the curve on the inside. If the bike shows signs of wobbling, ease up on the throttle and the lean (drift to the outside lane). You have more fixes to do. If no evidence of wobble, you’re done. Enjoy the Ride.

SOURCEDATA/REFERENCES: Me. I’m a mechanical engineer (30 years) in space systems (NASA, USAF, NOAA, NRO). Prior to that I was a Master Aircraft Tech(10 years); and prior to that a automobile and motorcycle mechanic (5years). Yes, I’m old ... been riding since ‘64 (Honda, Triumph, and Harley). As you can deduce, the wobble, sustained oscillation, is a complex issue involving physics (matter and motion), kinematics (geometryof motion), analytical dynamics (mass and moment of inertia), and mechanics (behaviorof physical bodies when subjected to forces or displacements). Solving it is not always one fix scenario. Every bike is different. Have I addressed everything? NOPE … else this post would be a text book! But hopefully I’ve managed to sum up and clarify the thousands of post on this subject and will help you fix your oscillationissues. Don’t have a wobble? Never had one? Never experienced one? You’re lucky. RIDE SAFE.

There is no substitute for courtesy or mutual respect. "If you can't say something nice, don't say nothin' at all" (Thumper, Bambi, Disney 1942)