I just joined the forum, but this is a good post...thanks

 

Really great thread with a Noble Prize winning OP - many thanks!

A few more cents:

1: the “wobbling” felt in sweepers can/may (can/may because we exclude front end, tire, alignment, wheel bearing and rear suspension issues) be caused because the rear wheel tracking accuracy is compromised by side to side movement of the swinging arm. The Swing arm is meant to travel up and down ONLY, not side to side. The forces on the swing up pivot in a bend can/may cause the side to side movement. As the swing arm pivot is connected to the chassis of the bike via flexible bushes via the transmission the whole plot relies on those flexible bushes to prevent the side to side movement. At best, when they are new, these bushes are able to prevent this movement as well as provide their primary function of insulating the Bike from engine vibration by allowing vertical (up/down) movement of the engine/transmission unit). Sometimes, it seems that even when new, they don’t. Side to side movement is allowed, swing arm and rear wheel, as a result, lose tracking accuracy. The aftermarket provides improved bushes mainly made from urethane as well as improved pivots that are great at maintaining vertical movement to insulate the vibes while at the same time keeping side to side at bay. The engine vibration causes mainly vertical movement, not (much) side to side. It should be noted that the cause of side to side movement is not engine vibes BUT the forces from the rear wheel. The Urethane material is also more resistant to degradation from fuels, oils and other yucky stuff it may come into contact with than the stock bushing material.

So, just buy some aftermarket urethane bushes and even the larger diameter stainless steel pivot rod that is available and problem solved right? Question is though, even with the improved pivot rod (assuming that is fitted), those poor bushes are still being subjected to the side to side forces from the back wheel and these forces are considerable. When fitted new and set up properly there is no question that new bushes (OEM or aftermarket) will manage the task. However, when not set up right or after a zillion cycles of the side to side forces applied by the rear wheel it makes sense that the bushes ability to resist side to side motion will degrade. This degradation means move movement in the wrong plane becomes possible to the extent that the rider can actually feel the effect when riding a curve. Wobble time.

So, forget the bushes and fit a brace then? Makes sense. Regardless of how fitted most use a heim joint to allow vertical and not side to side movement. They prevent side to side movement and if set up properly, allow the bushes to do their vibe insulation job. This means that set up does need to be right. If vertical movement is limited by the brace then vibes will be transmitted. Whatever, there are a number of really good heim joint based braces available and you don’t need to ask which is best, just think about what it is designed to do and you can see what works. IT HAS TO STOP the rear wheel generated forces from causing side to side movement at the swing arm pivot so needs to be a meaty enough piece of kit do perform this function. Problem is, what if the brace is installed as the solution but the bushes are shot or not set up right? Hmmmmm

So let’s think again. The bushes should insulate vibes by allowing up and down movement. They unfairly are asked to also prevent side to side movement. How about we put excellent quality new bushes in which will last for ever in terms of degradation from contamination and if they never have to resist side to side forces? The job of the brace then is to both maintain rear wheel tracking accuracy AND protect the bushes from fatigue from side to side forces.

OK, so new urethane bushes, new pivot rod AND a brace will both fix current and potential future wobble stuff? Hmmmmmm

Well now we move to few cents #2

2. #1 refers to forces generated by the contact patch of the rear tire transmitted via the wheel, bearings, swinging arm, swing arm pivot acting on the rear engine mount bushes to cause side to side movement. There, I said it. Rear engine mount bushes. Rear could also be “the middle point”. If we think about three points on our bike that influence the assemby’s Ability to maintain rear wheel tracking accuracy we could start at one end; front engine mount, come to (almost) the middle; rear engine mount and the the other end; tire contact patch.

As the force comes from the tire contact patch end, if we only anchor//insulate the middle we are putting all the work on our poor old bushes and brace...If we really want to protect our rear engine mount bushes and spread the load wouldn’t we also anchor the fron end too? Hmmmmmm

There are also great front engine mount braces available from the aftermarket. There are also aftermarket front end urethane bushes available.

So new front and rear engine mounts along with SSC pivot shaft from Glide - Pro and the non heim jointed stabiliser from Smooth Rider along with a Tru-Track front stabiliser would cost about the same as a fitted set of tires I guess, which is not cheap, but should fix current wobbles for good or, done as a preventative action, will make sure the wobble monster leaves your Bike alone.

 

The urethane bushings like glide-pro are pretty weak for use as the rear tranny mounts.. If you don't believe me add the mount leaving the little cover removed, place a dial indicator on the frame and a set the pointer on the center pivot. Jam a pry bar between the the swing arm and frame and pull. The indicator will show how much the bushings flex. Try different mounts. You can get an idea as to what works and what doesn't.





The stock ones aren't as bad for compression than the urethane ones. The reasons are that the rubber bonds better to steel than urethane and rubber bushings use added rings to keep the rubber from compressing. The urethane bushings don't..

The arm stuff is much better but you need to remember to check the spherical bearings on the arms and keep them lubed if they don't have covers.

 

I have been running the True-Track front and rear on my 14 LTD for 20,000 miles. They are a small company in So Cal with great customer support.

 

Great thread. I can't believe I had the attention span to read the whole thing! After reading this, what I originally thought was tire cupping issues on sweeping turns may just be this issue. While I love buying bling and aesthetic items for the ride, this seems like something that needs to come before anything else. Thanks OP!!

 

Well done for your determination! When I started it I didn't expect this thread to still be going. Seasons greetings and here's to a great riding season.

 

I replaced the swing arm bushings added a true track and a glide pro front mount and so far it is way better than before. I am looking forward to a day I can get some interstate riding in. That will be my final test for this set up. Bike seems more stable and more agile.

 

Sorry, haven't read through entire thread--anyone tried brace from Alloy Art? True trak looks great I just don't feel like dropping that much $.

https://www.alloyart.com/bagger/tour...-09-to-present

 

Million dollar question which many of us have. If you go back to my post (about 6up), there is still no definitive answer but I did try and describe the problem we try to solve with a brace. Understanding that (assuming you agree) means you can look at a brace photo and decide yourself if you think it is up to the job.

 

Be careful on your description, as you could be describing two different things here and it's not exactly clear which you mean.

If the swingarm is swinging side to side, that will turn the rear wheel, creating very unpleasant handling effects. If the swingarm is displacing side to side, the rear wheel alignment doesn't change, and the handling effect is nominal.

Personally, I found the former, and it was in the oem correct excessive clearance between the swingarm shaft and the swingarm inner bushings. I've found this excessive clearance in my bike, in the new replacement parts, and in swingarm assemblies I've handled at swap meets. This is well masked by belt tension when the bike is assembled.

I fixed this problem using stainless steel shim stock and the problem was cured. Alternatively one could make replacement inner bushings on a lathe.