Touring Chassis Design
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Outstanding HDF Member
Joined: Jan 2010
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From: earth
Touring Chassis Design
This probably isnt really a new thought for a lot of folks but, some elements of the HD touring chassis design are a fantastic engineering failure. Just look at all of the aftermarket products available to fix handling issues. To address the undesirable rear end wobulation on my SG, I personally tried the Sta-Bo and it worked very well. Im always in search of improving the ride, so I tried the Glide-Pro but I did not find that it was any noticeable improvement over the Sta-Bo. Anway, while I had the bike disassembled I started pondering on the design of the Drivetrain to Swingarm to Chassis Mount system (DSCM). I believe this DSCM is the root of most of the touring chassis handling issues. The swingarm is effectively rubber mounted, allowing unfavorable motion in multiple planes. When reading reviews about the many different stabilizing products, I noticed that most people claim great improvement but not an absolute cure. This makes sense because all of the available stabilizers limit motion in only 1 plane. During operation, the ever changing load from the road causes the rear end to momentarily flex out of alignment with the rest of the chassis. I believe this swingarm flex challenges the resistance of the rubber mount to the point where the mount stops giving and rebounds to its neutral position. If you are moving through a long sweeping turn, which is where most people report their problems, the constant load on the rear end could promote a cycle of flex and rebound, thereby creating the Wobble. I started thinking about the many motorcycles I have owned and I could not recall any with a swingarm that didnt have a hard pivot point, directly mounted to the main chassis. Out of curiosity, I visited all of the local motorcycle shops to compare current designs. Granted I did not get to see every machine in production today, but I did not see any other manufacturer besides Harley using an integrated DSCM concept. Even the improved 2009 and up chassis still employs this same weak link design. The Dyna chassis is similar, but apparently far more effective at resisting undesirable motion in the swingarm. I dont think it is a coincidence that no other manufacturer incorporates this integrated mount concept. Harley got this one terribly wrong and for some reason they still havent fixed it. Again, Im sure this is not a new eureka discovery to a lot of folks, but it has newly attracted my attention. Anyway, these are just my unsubstantiated theories about the Touring Chassis. I would like to know what others think about the subject.
Road Master
Joined: Nov 2010
Posts: 1,156
Likes: 1
From: Nebraska
Pop out the rubber isolators and machine them from stainless....pop them back in....problem solved. New problem.......vibration. Why couldnt they instead of rubber mounting the swing arm.....ditch the isolators and mount the ends of the pivot shaft solid then rubber mount the tranny to the pivot pin. Enlarge the mount on the trans so that a cleve block type bearing could be inserted.
I recently upgraded my 99 FLHRCI's swingarm to an 09 one. Did the whole thing with a 3/4 pivot pin and the spherical bearings. I bored the mount in the trans to accept the new pin. I only had the wobble a few times but it did scare me a bit. Another reason for the change was that ive seen a few older swingarms from like 90-99s crack above the rear axle. That worried me more than the wobble. That and i wanted that rear axle with the cam style adjusters. Super nice...no more measuring for wheel alignment.
I recently upgraded my 99 FLHRCI's swingarm to an 09 one. Did the whole thing with a 3/4 pivot pin and the spherical bearings. I bored the mount in the trans to accept the new pin. I only had the wobble a few times but it did scare me a bit. Another reason for the change was that ive seen a few older swingarms from like 90-99s crack above the rear axle. That worried me more than the wobble. That and i wanted that rear axle with the cam style adjusters. Super nice...no more measuring for wheel alignment.
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