Swing arm clearance to frame

[Boertjie]

Hi Folks,
Should the clearance be 100% the same on both sides of the swinging arm to frame connection. Mine is currently 4.2mm on one side and 4.7mm on the other. My bike starts to weave slightly from 120km/h onwards and get worse at higher speeds. I want to explore all possibilities for this, as this is driving me nuts!

Thanks!

[Garnet]

The back wheel has about 4mm of offset built into it so I would not think that .5 of a mm at the swing arm would trigger a weave. It may make it worse once started, I don't know.

I would be much more concerned with alingment, are both wheels pointing the same direction on all planes. Tire condition and presures and tire balance all play a role. It's a tough subject that I have been lucky enough to avoid all these years.

[Boertjie]

The back wheel has about 4mm of offset built into it so I would not think that .5 of a mm at the swing arm would trigger a weave. It may make it worse once started, I don't know.

I would be much more concerned with alingment, are both wheels pointing the same direction on all planes. Tire condition and presures and tire balance all play a role. It's a tough subject that I have been lucky enough to avoid all these years.

Thanks, yes will definitely have a look at the tire balance as well.

[Roy Gavin]

Remember when adjusting the bearings that you over tighten them to about 10 lbs then slacken them off and re adjust to 3/4 lbs.
It also mat be that the bearings are turning on the pivot pins - so pull the drive side pin and check for wear- DAHIK.
More common on monos and paralevers, of course.

You dont say which bike , but the rear paralever pivots dont have to be far out to cause a nasty weave either---.

[dwire]

Good advice to the OP everyone. The mention of preload IS critical; messing up and forgetting to re-torque the front axle bolt cured my ways permantly once, for finger tight IS NOT the spec... I was smart enough to notice something was wrong and pull over immediately and check the nut and returned and set it correctly before going back out. Fortunately I noticed something was "not right" in about 2/10th of a mile at slow speeds, so it was nothing more than a permanent lesson in practicing due diligence for me.

I am wondering, no one mentioned fork alignment. Is there some reason for this; did I not understand the symptoms? - A mid to high speed weaving/wobbling? Once you've covered all the obvious, including that the frame is straight, I'd think fork alignment might be something to consider once tires, wheels/balancing, bearings and frame alignment have been covered. Duane Ausherman has wonderful information on all of these topics if you are not already an expert.

Experts rail me please if this seems bad advice...

Good luck, proceed safely and when you determine the root cause, please post your findings as to help others that may wonder upon the forum for answers.

[Duane Ausherman]

In theory, the swing arm should be centered. However, it isn't really important. Very few chain drive bikes have the two wheels in a straight line. I have ridden behind bikes with one an inch off of track. Almost none are as close as your bike with an error of only .25 mm.

In practice, I don't consider centering to be important at all. Few know what a bike has been through over the years. That box section can get bent fairly easily.

Far more important is for the driveshaft to not wear itself down on the swing arm. Pull the boot back and check visually to see if the driveshaft is centered in the tube. It is far more important to protect the driveshaft than worry about equal spacing.

I have seen them turn themselves down by rubbing on compression or extension of the rear suspension.

Do not follow the workshop procedure for tightening the swing arm bearings. They are crazy....... and wrong. Tighten it so that the play goes away and it has a super slight bit of preload. The factory method will produce way too much play and notch those bearings quickly.

Be sure to give each side a squirt of new grease a few times a year and especially after riding in rain.

[Boertjie]

Thanks all, the wheel bearings are new and preloaded correctly, BUT I remember one of the bearings either front or rear being a bit loose in the hub. I wouldn't say spin in the hub loose. This is also when I draw up this drawing of the front wheel shaft and bearings, anyone remember? It was on the old forum.

[melville]

Thanks all, the wheel bearings are new and preloaded correctly, BUT I remember one of the bearings either front or rear being a bit loose in the hub. I wouldn't say spin in the hub loose. This is also when I draw up this drawing of the front wheel shaft and bearings, anyone remember? It was on the old forum.

Oh, we remember! Turned into an FH thread.

[Boertjie]

Thanks all, the wheel bearings are new and preloaded correctly, BUT I remember one of the bearings either front or rear being a bit loose in the hub. I wouldn't say spin in the hub loose. This is also when I draw up this drawing of the front wheel shaft and bearings, anyone remember? It was on the old forum.

Oh, we remember! Turned into an FH thread.

Ah..yes..what happened to FH and GSPD??

[ME 109]

Thanks all, the wheel bearings are new and preloaded correctly, BUT I remember one of the bearings either front or rear being a bit loose in the hub. I wouldn't say spin in the hub loose. This is also when I draw up this drawing of the front wheel shaft and bearings, anyone remember? It was on the old forum.

Oh, we remember! Turned into an FH thread.

Ah..yes..what happened to FH and GSPD??

Fun took forced redundancy and GSPD is prolly in the Bahamas somewhere.