Chainsaw opines on the “Harley Death Wobble”

There are two things you don’t want to hear in the same sentence:  “Harley” and “Death Wobble”.

I came across this story from KPHO Phoenix which describes the phenomenon:

A camera mounted on a Georgia state trooper’s police-issued Harley shows Officer Richard Barber traveling 90 mph along an interstate. His 2007 Harley Electra Glide begins to shimmy and wobble. Eventually, Barber is able to stop the bike safely.

 But a Raleigh, N.C., police officer was not so lucky. In 2002, 30-year-old Charles Paul was thrown from his Harley Electra Glide after it began to wobble. He died, and his family later settled a wrongful death suit with Harley-Davidson in 2008.

KPHO’s video on the topic can be found here.

Uh, really ? It gave me some pause since we ride a 2005 Ultra Classic, but not being versed in the ins and outs of the whole thing, I asked my resident expert Chainsaw.

As usual, I got a thorough answer, though perhaps more than I bargained for.

Here is his reply, written as only Chainsaw can write it:

You don’t ask the easy questions, do you?

There are a lot of things at work here, and I’m gonna tell ya more than ya expected to know.

In 1980 there were only 2 bikes that had rubber mounted motors.  The earlier models were bolted through a motor mount boss welded onto the frame, through a corresponding cast aluminum bolt hole in the bottom end or engine cases that housed the flywheels, crankshaft, piston rods and oil pump.

The one and only touring bike at the time, the FLT, was rubber mounted, and the one and only rubber mounted FX, was the FXB, or the “Sturgis” model, and it was the 1st belt drive bike.

By 1985 all models, except maybe Sportsters, were rubber mounted motors, and the Shovelhead engine had been replaced by the new “Evo” or 80 inch (1340cc) Evolution engine.

That’s when the “overnight sensations” and yuppies began to appear on the roads because the Evo motor was proported to be as tight as a thermos bottle, and wouldn’t leak oil. That was appealing to the morons that just wanted to ride and show off that they owned a Harley.

Well, I’ve dropped a thermos before.

Evos were a tight motor, and still are today.  Some folks still swear by them, but they don’t last long on an 800+lb touring bike, and these are the bikes that I am going to refer to as they have in the story.

Since the 90’s, the motors and transmissions have been “rubber mounted” with massively dense rubber bushings to the frame and swingarm in the FLH family of bikes:  Road King, Street Glide, Electra Glide Standard, Electra Glide Classic, Electra Glide Ultra Classic, Road Glide, or any bastardization of those models, either for Police use, a Custom Vehicle Operations bike  which usually have a 103″ – 110″ motor on the frame, slinging massive amounts of torque to the motor mounts and swingarm mounts.

The motor bushings do wear out after a bunch of miles and normal service.

Sometimes the bikes come from the factory poorly assembled and they wobble around 80 mph, but you turn right around and go back to the dealer and tell them to shove the piece of shit up their ass, and tell them to get the paperwork out and rewrite the deal on another bike.

Then there’s the final key piece to this puzzle that Harley-Davidson won’t admit to being a factor in the “Wobble Syndrome.”

Anyone that has gotten down on the ground and looked at how the motor and transmission are mounted on the bike, or is a mechanic, will see that the transmission is not solid mounted to the frame per se, it is mounted through those dense bushings that do double duty as engine mounts and swingarm mounts.

That is the weak link in the whole scenario.

A little bit of physics knowledge will tell you that the swingarm is for the rear suspension or shocks,  for up and down vertical travel, not side to side horizontal travel, yet the motor and transmission are hard mounted together, and the rear of the  transmission mounts to the swingarm pivot point.

That’s why when I kept saying a while back that the front and rear wheel on our ’05 Ultra didn’t seem to track along the same line, it’s because the back wheel had thrown a wheel weight, and when I got a new tire put on and they balanced it, that shit was gone.  Just that little bit of that weight being thrown on changed the physics and performance of the pivot point rubber mount on the swingarm.

We’ve not had any issues with the “wobble syndrome” because of the way that I ride – I feel the bike, I listen to the bike, I become part of the bike, and if something is not quite right, I know it immediately, even when the bike is loaded down, pulling a fully loaded trailer.  I can feel the horizontal forces, but I ride accordingly.

There is a part on the market that solves the horizontal effects on the swingarm pivot point, and that is all that is required to give that particular set of bushings a gazillion miles of dependability and service.   You’ll notice on their website, a picture of someone laying hard into a corner. That’s what this is all about, the sideways, lateral forces that put the load on the swingarm bushings. At their products link, the year models of applications correspond to the beefiness of the product as the year model of bikes go up in motor size and horsepower – factory horsepower that is, not hot rodding a motor to unreasonable cubic inches like Checkered Bob’s 124″ desires.

The thing that people, and the goddamned media don’t realize  is that the laced wheel or spokes were not designed to carry the weights that touring bikes carry now -You have the weight of the bike itself (approximately 800 lbs), the rider and passenger weights which can vary anywhere from 350lbs to 500lbs…. add that together with the kinetic force of real time riding, and the swingarm pivot point bushings are performing under the pressure of over a ton.  Factor in the dainty (but cooool looking – not in my opinion) laced spoke wheels and you have a 2nd issue that can spell disaster.

That’s why Harley-Davidson and the report made mention of, “added on parts.”  You’ll also notice that neither one mentioned what add on parts they were referring to.

It’s the laced spoke wheels, or anything that adds weight to them is when the dangerous natural lateral forces come into play.

The reason that “other” manufacturers’ bikes don’t do it is because of initial standing weights and the motor mounting and drive trains are completely different.

You can’t compare apples to oranges.

The Police bikes that they referred to that went out of control needed a  steering damper,  not so much the tru-track motor/tranny/swingarm brace, as the damper is used for speed and stability.  The tru-track may have helped, but what would’ve helped out more would have been a tighter maintenance schedule as those bikes get the bejesus beat out of them and if your machine’s key components are held together with rubber bushings, they will wear faster.

This article got me pissed off.  It shows how naive the general riding public and media are. 

Hell, I’m done with this subject, I gotta go take a dump.



Filed under Uncategorized

9 responses to “Chainsaw opines on the “Harley Death Wobble”

  1. Royal Enfield’s new C5 bikes can have similar issues at highway speeds if the rear suspension isn’t set up quite right. But since they’re 500cc thumpers, it doesn’t come up as much because few people really get them up that fast.

  2. lisen

    Finally an answer one can take to the loo. 🙂

  3. boogie

    Chainsaw! Remember the old right side drive hard tails? Same issue. With the Primary pullin one way and the drive sprocket/rear drum pullin the other, I had a WL give the warblwobble from hell. Not put horizontally to the road though. It had a chatter effect from engine stroke, through primary to tranny, to the rear wheel. As one compressed, the other was slacking, and shot the torgue back up to the other.
    It wouldn’t make a horizontal rear end movement, but at the one low RPM in 2nd gear, it freaked me out for years.
    Now I know why that clutch gear got kicked and they put the drive on the left side. (xept those stupid sportys)

    • Chainsaw

      That WL was probably your pride and joy, and gave you as much trouble as it did great memories.
      I’d be willing to bet that you’re wishing that you still had it, lugging 2nd gear wobble or not, right?
      I had one of those right drive/right shift Sporties.
      It was my 1st H-D and boy was I proud!
      The boy wanted $2000.00 for it, I got him down to $1200.00 – those days are long gone.
      It was a 900c.c.’65 Ironhead on a stock frame that had a weld on/bolt on, Jammer hardtail that stretched it 6″, and lowered it 2″, (almost like sitting on a 5-gallon bucket) and it made the chain almost 7′ long and require two masterlinks, until I started buying machine chain from an industrial supplier, but you could still throw a cat between the tranny cases an the front of the rear wheel.
      I christened it, “The Fudgepacker”, because to get any suspension out of it, you had to run the back tire a tad low on air, and watch out for cigarette butts, bottle caps, roadkill, and too many coats of paint on crosswalks at intersections – they could be like crossing railroad tracks at times.
      It ran a ’72 front end with a disc brake, and never had the rear crossover put on the new frame setup for the rear brake.
      It didn’t bother me none, between the disc on the front and the tranny, I had no problem gettin’ her to stop.
      It was magneto fired, and the electrics came from a two brush generator, battery not required, and it had all of three wires running the show.
      One for the headlight, one for the tail light, and a ground wire – that’s when I didn’t get it up around 65 mph and the brushes vibrated off of the armature and kill the juice to the headlight and if seen, the man would pull me over and write me an equipment violation citation.
      The magneto ran 180 degrees out of what the stock timing setting called for.
      Be damned if I know, but that’s the only way it would fire up and run.
      I had it tied off to the front pushrod tube with a stiff screen door spring in case the mag bolt started to get loose.
      It was a real bitch to crank too.
      It didn’t matter if the motor was hot or cold.
      You could kick, and kick, and kick, until you were ready to keel over, and it would sit there, grinning at me.
      There were times, new points or not, you could just about tell it to fire, and it would, but more often than not, on a run everyone would have to wait for me to get to kickin’ first before they hit their push buttons.
      As much of a pain in ass that bike was, I damned near rode the wheels off of it.
      I went through 3 top end jobs, about 9 machine chains, and a whollllle lotta Ching-Chong (Cheng Shin) tires ‘cuz back then they were like $30 a pop from the Jap bike shop, and the ‘Packer could do a burnout like no one’s business, as long as you stood up off of the seat.
      Once you plopped down onto the seat, it would just bark the tire, and chug away like an old Massey-Ferguson.

  4. Bill Smith

    Given the steering geometry, If it were head shake, they would’ve been able to pull it back in. Even if you were racing a Harley, you wouldn’t need a steering stabilizer. The geometry is very relaxed. Those accidents were caused by movement at the rear motor mount. It’s a known issue. Once it starts, there’s nothing you can do but ride it out. It’s the scariest thing I’ve experienced on a motorcycle. Buells don’t oscillate like Harleys do because they have a 3rd stabilizer link. Every sporty based buell since day one has a 3rd link. Buell took out a patent about this issue. It doesn’t take a physics expert to understand that to stabilize a plane (the motor and drive train) requires 3 points that don’t move. When you only have 2 points. it can rotate around the axis between those two points. Movement is only limited by the squishy rubber bushings on the rear swing arm pivot. Keep in mind that the bike weighs several hundred pounds and the forces on the frame are focused on that point when you lean over. It wouldn’t be in issue if the rear wheel didn’t move with the engine, but since it does, the rear wheel can pivot around the axis between the two stabilizers on the engine. The effect is the rear wheel to front wheel alignment changing as you ride.

    When it happens, it feels like the bike is hinging under your seat and there’s nothing you can do about it. It doesn’t let up as you let off, or throttle up. As the rear mounts age, they have more play and give and it becomes more obvious. Buy an aftermarket stabilizer. You won’t regret it.

    You don’t feel this wobble “coming on” like a steering wobble so you can’t “adjust your riding appropriately”. It is also not brought on by over-driving the bike, or pushing it too hard. You can ride for 10 hours and feel nothing and hitting a small bump or rut in a corner can set it off with no warning. Laced wheels are not the cause of this problem. Properly engineered “laced” wheels could support a motorcycle that weighed 10,000 lbs. If you’re running laced wheels off a 150lb honda on a 700lb bike, you have a problem, but if the wheels are designed for the bike, they will work fine. Yes, laced wheels flex more than cast aluminum mags. Steel is more flexible than cast aluminum, but it doesn’t cause instability. Look at other manufacturers that use laced wheels. Yamaha, Victory, Honda, etc. have all used laced wheels on similarly sized bikes. Their bikes don’t have stability issues. The unique thing about these bikes is the motor mounting system. It is designed to allow the motor to vibrate in the frame without transferring 100% of the motion to the frame. The swing arm has to be attached to the drive train rather than the frame so that the belt doesn’t jump teeth when the motor moves. None of the competitors have this type of mounting system. They balance the engine to limit vibration and attach the swing arm to the frame instead of the engine.

    In my experience, loading the bike down with passenger and gear actually reduces the wobble. My guess is that the added mass slows the oscillations. More mass means more inertia and slower changes in motion with equivalent force applied.

    If you experience this wobble, you will know it.

  5. Joh Havenhill

    I have a 2004 Road king with a 124″ 153 hp, 150 lbs TRQ added a fairing progressive shocks front and back. A new up graded swing arm from glide pro. A progressive transmission stabilizer link . I have added progressive front schocks the best money can buy and I still expierence the death wobble in turns and and hi speeds, my biike will run tens in the quaters mile, however, every time I shift the bike it wobbles as the front re weights after each shift, scrary as hell! Last year I had about 200lbs of wieght in route to Stugis on my seat and back back rest. I achived 145+ mph in stright line while slowly climbing to said speed then the bike started to wobble!
    This was near The Salt falts. It will not achive those speeds with just me on the bike. Latley the bike is wobbleling at various speeds.
    It was suggested that I put a new more rounded front tire like a Micelon and or the new smart Dunlap tire. I know that my frame and bike are over stressed by the extra HP but the extra HP only confirms the weak links
    often shared on these open fourms. Any buddy a real non sarcastic suggesstion?
    Please let me know.

    John Havenhill,911 tribute bike.
    Captain ,Alameda County Fire Dept.

  6. Kevin DeHennis

    I’ve ridden bikes for the last 48 years, all types from the old suicide clutch knucklehead, a dresser, shovelhead, sportsters and an assortment of Jap bikes. I recently bought a 2001 1200 sportster and have experienced my “first” high speed wobble. It starts mildly at 65 mph, then gets progressively worse. It’s an every day occurance. I’ve been reading all these blogs and they blame it on 25 different things, all of which I’ve checked, new tires, good mounts, fork oil, bushings etc. etc and the damn thing still wobbles. Not every bike does this, so my feeling is this bike is a lemon.

    • Franky

      Sounds like a tire balance issue with your Sporty, or worn rear swingarm bushings. The Sporty is not rubber mounted engine for 2001.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s