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. I find this to be more likely on any I have fixed. But........most won't do,the work to R+R complete front end to verify good cups and bearings. Easer to bolt something on plus I guess it's to cheap with 2 bearings only costing 20 bucks total lol
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.
What is the difference between "swinging? and "displacing"?
What is the difference between "swinging? and "displacing"?
Displacing is moving on the axle moving the swing arm and wheel laterally. Front and rear wheel will be somewhat out of alignment but headed in the same direction
Swinging is moving at angles by compressing the rubber mounts, sort of like a dog wags its tail. The rear wheel steers as its vector points into a different direction than the front wheel (assuming there's no steering input to the front wheel)
Last edited by Andreas; Jan 2, 2018 at 11:19 AM.
Reason: typo
Displacing is moving on the axle moving the swing arm and wheel laterally. Front and rear wheel will be somewhat out of alignment but headed in the same direction
Swinging is moving at angles by compressing the rubber mounts, sort of like a dog wags its tail. The rear wheel steers as its vector points into a different direction than the front wheel (assuming there's no steering input to the front wheel)
What is " moving on the axle moving the swing arm "? Swing-arm sliding a little side to side? That should be tight if the pivot nuts are tight and bearings good.
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...
Interesting stuff Max - looking at your photo the pry bar is not going to generate as much side to side movement as up and down. The dial gauge will for sure register movement with the unnatural source of force applied that way but surely the measurement should be done at the centre of the rear axle relative to the centre point of the frame in a way that measures side to side movement as that is the dynamic that causes the wobble.
What is " moving on the axle moving the swing arm "? Swing-arm sliding a little side to side? That should be tight if the pivot nuts are tight and bearings good.
Don't understand..
The poster who I responded to vaguely described side to side motion because of the allegedly squishy frame mount bushings the swingarm axle goes through.
If the bushings are squishy side to side, the swingarm axle can be moving side to side, moving the swingarm with the axle, side to side. There would be no angular deflection of the rear wheel, just the whole thing moving its track a little bit to the right or a little bit to the left.
If the bushings are squishy fore and aft, the swingarm axle can be twisting, causing the swingarm itself to be swinging, causing the rear wheel to be turned to the left or the right. This would then steer the rear of the bike to the left or the right.
Two very different effects, with very different results. If the axle/swingarm and rear tire are simply displacing a little to the left or right, you could feel a little shifting of the bike as it does so. If the axle/swingarm and rear tire are turning to the left or right, you would feel the bike turning underneath you as it did so.
There are lots of assumptions that because the frame/axle bushing is black and rubber to the eye that it must be a soft squishy thing. It's not actually, being made of stacked steel discs as well rubber. Many also observe it's unusual shape and incorrectly conclude that it has sagged or deformed in use.
Interesting stuff Max - looking at your photo the pry bar is not going to generate as much side to side movement as up and down. The dial gauge will for sure register movement with the unnatural source of force applied that way but surely the measurement should be done at the centre of the rear axle relative to the centre point of the frame in a way that measures side to side movement as that is the dynamic that causes the wobble.
How does the pry bar generate vertical forces? I'm prying between the swingarm and the frame.. I have to push horizontally on the pry bar.. It's moves the pivot axle movement referenced to the frame which says the bushing on the opposite side is compressing.. Going to the rear axle will show greater movement but then you really are not seeing the flex at the rubber isolators. There is definitely more than one source of flex. Lower frame rails support the bushings are also flexing but not as much as the rubber is compressing.
The side to side flexing stems from loaded weight and side thrusts caused by the load on the rear wheel. The pry-bar simply attempts to emulate the side trust.
The poster who I responded to vaguely described side to side motion because of the allegedly squishy frame mount bushings the swingarm axle goes through.
If the bushings are squishy side to side, the swingarm axle can be moving side to side, moving the swingarm with the axle, side to side. There would be no angular deflection of the rear wheel, just the whole thing moving its track a little bit to the right or a little bit to the left.
If the bushings are squishy fore and aft, the swingarm axle can be twisting, causing the swingarm itself to be swinging, causing the rear wheel to be turned to the left or the right. This would then steer the rear of the bike to the left or the right.
Two very different effects, with very different results. If the axle/swingarm and rear tire are simply displacing a little to the left or right, you could feel a little shifting of the bike as it does so. If the axle/swingarm and rear tire are turning to the left or right, you would feel the bike turning underneath you as it did so.
There are lots of assumptions that because the frame/axle bushing is black and rubber to the eye that it must be a soft squishy thing. It's not actually, being made of stacked steel discs as well rubber. Many also observe it's unusual shape and incorrectly conclude that it has sagged or deformed in use.
Still not sure I understand.. The rubber bushing should allow freedom of movement radially in the plane perpendicular to the axis of the swing arm pivot axle. The vibration it needs to isolate is a radial force that is perpendicular to the axis of the crank caused by the imbalance of the motor. The motor/tranny should be able to move front to back and not upset alignment.. And it does.. As the rear shocks compress, they pull the motor back. Under acceleration the motor moves forward.
Nice pic on the cutaway of the bushing BTW. The rings are to limit compression but allow radial movement..
Great write up and explanation. I would like to know more then what was changed on the Rushmores. My 2013 RGU had a horrible wobble from brand new. But my 2014 Limited has never had it and I have over 100k miles on the original mounts, bushings, etc. The only change was replacing the steering neck bearings during the 100k service.
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plus I guess it's to cheap with 2 bearings only costing 20 bucks total lol
