Curing Bagger Wobble - HRBW Tech

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Anyone who has ridden one of the new H-D baggers and really put it through its paces has probably experienced that infamous shimmy, or wobble. The same thing that makes these bikes so smooth to the rider and passenger is basically what causes it: the rubber-mounted engine and transmission. Well, that's not totally true; there are a lot of other factors, like the bike's weight, the way that the swingarm attaches to the back of the transmission, and an aggressive riding style. Take all of these ingredients, toss in some uneven pavement or some grooved concrete, and you will get a dreaded case of bagger shimmy.

Basically, a couple of different things can cause it. One is that when a rider is riding aggressively and goes into a corner, there is considerable pressure applied to the rear of the bike that makes the whole rear suspension want to deflect (basically, stand back up). Well, that pressure pulls on the back of the transmission case, which in turn pulls on the primary drive and the engine. The rubber mounts initially give, then they push back, and this movement of the engine and transmission starts a vicious cycle that makes the back of the bike shimmy. In the second scenario it is the same thing that causes it, but it happens when you hit those evenly spaced "waves" on a concrete highway during acceleration. It starts pulling back on the swingarm while the engine is trying to pull the bike forward. Again the tug-o-war starts between the pressure being applied to the rear wheel and swingarm, and the engine and transmission and all of it (motor, tranny, swingarm, etc.) starts rocking around inside the chassis on the rubber engine and transmission mounts. That rocking of the entire drivetrain turns into a shimmy or wobble felt by the rider.

Well, James Crosby from Alloy Art decided that he'd had enough of his bagger shimmying down the highway, and put it up on the lift at the shop to see if there was anything he could do to tie everything together and stop the shimmy. He found a suitable place to anchor the bottom of the transmission to the frame and thanks to the fact that he had some heim joints lying around the shop, built a rough prototype. The prototype cured the problem, but it transferred all of the vibration from the engine through the chassis. So he worked up the next version that had a bushing in the center of the wishbone link to absorb the vibration, and kept refining the part to cut out the majority of the vibration while still anchoring the transmission to the chassis until they were happy. Then they duplicated it for the production kit.

The Touring XR from Alloy Art is an amazingly simple part to install, taking James only a half-hour with standard hand tools. And having had the opportunity to ride the bike both before and after the installation of the kit, we can attest to the difference in the way the bike handles-it was like riding two different motorcycles. After the kit was installed, we threw the bike into a corner at highway speed without so much as a hiccup. The Alloy Art kit comes in right around $400.00 retail, so those of you interested in picking one up can use the contact information in the source box.