The other day I felt like poking around in the garage, so I decided to change the rod-ends on my top stabilizer link. I've had a solid link there for awhile (intended for a SBC alternator belt tensioner), but the ends were cheap and often needed lubrication to avoid loud squeaking. I followed cggorman's lead and ordered a much nicer set from Midwestern Supply, but kept my original jack screw/turnbuckle.



I did my alignment the way I always do, both wheels in the air, center bolt loose in the Predator front mount, magnetic levels on the the top of the frame and the rear brake disk. No problem anywhere, everything aligned right up to zero degrees all around. But I did notice something... When I installed the new link, I bolted the right side down, and then turned the adjuster until the hole lined up on the left and installed the second bolt. The top link was now fully installed, in a neutral position. It could easily be moved around by hand. Then I went through my alignment, until everything zeroed out. At this point, the top link had a lot of tension on it, and couldn't be moved by hand. With the bike on the side stand, the link goes back into a neutral state. But not when upright.

I'm now thinking that alignment should really only be done with the rear mount loose as well. If the front mount is loose, the bikes in the air, and there's tension on the top link, I assume that comes from the rear mount. If it aligns in this position, I assume the rear mount is under a little bit of stress when upright, possibly causing increased wear and more vibration. My bike doesn't vibrate really badly when riding, but there's probably room for improvement.

I didn't have time to get into the rear mount, so I left it for now. It rides well. I'm tending to some family stuff out of town this week, but when I'm back maybe I'll do it right. I'm assuming (hoping) that the top link feels unloaded when in alignment if both mounts are loose.

But maybe it won't. Maybe the happy place where the engine/frame like to settle-in isn't perfectly aligned... In that case, are alignment and vibration inherently at odds with each other?

 

interesting. i did my alignment on the ground just with a jack under the kickstand to get it level. if you were to make the rear mount loose then you would be fighting the rear alignment since the transmission and swingarm would now be drooping...correct?

 

Correct, if not supported somewhere.

Of course, I may be over (and maybe under) thinking this whole thing...

 

im thinking over lol!

 

Excellent observations. I'm sure many are aware that I've given this topic quite a lot of thought in anticipation of my own alignment (get a move on, Gorman!)

My plan is to set up the front and rear lateral adjustments so the swingarm is centered in the frame and parallel to the long axis of the bike. After that I'll adjust the top link for parallel axles on the horizontal plane (vertical rotors).

I hadn't given much thought to whether or not the bike should be raised or lowered. Seems like it really should be done as close to the laden weight as is reasonable, but for those of us with three stabilizer links, I wouldn't expect it to make much difference. That doesn't take isolator tension into account, though. I'm honestly not very concerned about vibration since my bike is little more than a bar hopper.

Interesting...

 

I also verified what I expected to be true... Using the front rotor to compare with the rear rotor is worthless, without first performing a very careful string or laser alignment between the two wheels, and making sure that nothing moves the fork at all. With my magnetic inclinometer on the front rotor, I was able to get all sorts of different readings with just the slightest lateral tap against the front wheel (way less movement needed than what you can easily eyeball - it "looked" straight the whole time). Even with my relatively steep 28 degrees of rake, front wheel camber changes A LOT the moment the forks move at all.

 

hmmmmmm. i wish there were alignment bars so to speak. say a bar with sockets on the end that go over the axle nuts and hold the wheels perfectly straight. something solid that would make you have to do such a tedious string alignment. hmmmmmm

 

When you do an alignment the rear mount is supposed to be loose, as well as the front one. Once centered and aligned you run the bike for fifteen seconds to make it find its happy spot. Then tighten everything down.

 

Yup, agreed. I always let it run with the front mount loose, and this time I did so before attaching both sides of the top link. I'll figure out a way to run it with the rear mount loose... It's just easier to reach it with the pipe off on my bike (but should be possible just moving the rear m/c).