I've got a little head shaking going on

[Duane Ausherman]

With the LWB a bike tolerates a lot of varieties of loads.

This is about the SWB only. Two up and a load similar to ME-109's photo can work just fine. However, many times an owner would come in and complain that they had perfect stability on the ride to the camping area. (Highly doubtful) Then the passenger would be making camp and the rider would go do an errand. The bike would wobble very badly and easily around the 35-45 mph area. The blank space in the profile where the passenger had been was enough to cause instability.

My first R90S that I sold came back in the first few hundred miles with the owner complaining of a wobble. I told him that his top box was the cause. He said, "It is empty and only weights 3 lbs. because it is made of some XYZ magic stuff, so that can't be it." I told him to remove the box and test it out. He did and came back with egg on his face. It was stable without that aerodynamic mess hanging out in the air.

He was a good friend of the shop and didn't get 3000 miles on the R90S before being killed in a light plane crash at the Grand Canyon. It was a hot day and the plane didn't get out of ground affect.

All of the comments about having good tires and proper air pressure are spot on. You also MUST have the wheels balanced. And not with that magic glue stuff.

[Mal S7]

My 100/7 has always shaken its head when slowing down from about 80km and lifting one hand off the bars.Nothing too scary, just a quick unsettling wave.

Its gone away since I increased the fork-sag by about 20mm, though I also changed steering head bearings (with a fraction less pre-load than I normally would use) and carefully balanced the wheel and upped the front tire pressure so maybe it was one or all of these things.

[ME 109]

That reminds me Mal, a wheel that is not true has just what it takes to give birth to a wheel wobble.

[buzz]

Over time a head shake has reminded me it is time to replace the front tyre (or tire for some)

[Chuey]

The original post said that there is a bit of looseness in the bearings. I'm under the impression that there should be a bit of pre-load on the bearings.

My R100S with brand new tires, balanced and on snowflakes, new bearings, aligned fork, with a big tank bag (not really heavy) and two Krauser panniers has an annoying wobble tendency at just under 40mph. When riding in Yellowstone park, the speed limit is 45mph so you're around that speed the whole way. It is annoying. It does go away at higher speeds but I still do not expect my bikes to shake. (No top box, no pillion.)

Chuey

[ME 109]

What front air pressure Chuey?
I've had exactly what you describe, and I've a feeling so has everyone else.
Experiment with your headstem preload and check the wheel for true.
Check swing arm centreing and experiment.
If your happy with fork alignment, no point going there.

[Duane Ausherman]

A wheel that isn't true can certainly make it wobble. Test it with a dial gauge and put it on the inside of the rim, not the outside. If it is really bad, then you can see it by eye and confirm it with the dial on the outside, but for accuracy, test it on the inside.

Ignore the weld, as it can jump .010" easily. Otherwise the run-out should be small, say less than .010" and at around .020" it may make trouble. I say "may" because the tire tread design is very important. If you have knobby tires, then a larger error in rim alignment can be tolerated. If the tire is ribbed, then it is more important to be true.

[chasbmw]

I find that a wobble when deaccelerating through 30-40 mph is usually due to the head bearings being too loose. Just tighten in 2mm increments until the wobble goes away. If the bike sways form side to side along its longitudinal axis, then the bearings are too tight.

New bearings will need adjusting over the first 1000 miles of so as they settle down into their final positions. Adjusting the head bearings was always part of an airheads first service.

[Jean]

No one has mentioned soft or used-up shocks on the REAR yet.
With loaded panniers, this becomes an issue, too. One side may not be working the same as the other.
Do the cases fit TIGHT on their frames? Check this too.

[ME 109]

Another consideration is 'what starts the wobble'?

As plenty of us have experienced, it's a growing thing.
Mostly happens under the same circumstances of deceleration below 35-40 mph, when hands are removed from the bars, or grip lightened.

Since swapping my original front snowflake for a good, true s/hand one, the front end is much better behaved. My old front flake was at the point where I could really feel the warp/s when going around a smooth, tight bend in 2nd gear.
I could also pick it going in a straight line @ about 30-35 mph.

Once the flakes get over that magical 35-40 mph things start to settle because the gyroscopic effect of a heavy wheel takes over, preventing the wobble to a great degree,

I think we need to separate what causes the wobble to start, from what exacerbates the wobble.

What starts the wobble could be wheel warp/buckle, warp/buckle combined with unbalanced wheel, faulty tyre, incorrectly seated tyre, road surface etc.
I think low front tyre pressure doesn't change dynamics greatly from high pressure, should act as a dampener if anyhting..............still trying to get my head around that one.

Things that exacerbate wobble would be loose steering head bearings, fork misalignment, flattened off rear tyre causing levering/flexing/loading of the swingarm, bent frame, one side defective shock, unequal side to side luggage load, big empty top box, all things mentioned in what starts the wobble.
Edit, transfer to front wheel of centre of mass due to deceleration, change of rake?

To me, 'the wobble' is a build up and release of energy due to flex.
Can we eliminate effect by preventing the cause?

Just rambling, time to go to bed. ZZZZZZZZZZZZZZ