Mk2 rear wheel and break drum imbalance

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slimslowslider

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With swing arm in the vice for an alignment check, and cush rubbers removed, I noticed the imbalance in wheel and drum, looks and sounds like this (warning: may be considered boring..):

[video]http://www.youtube.com/watch?v=hUIJNpF3Zp0&feature=player_detailpage#t=20s[/video]
 
Boring?? How could you possibly think we would find that boring. That was without a doubt the most exciting film of a rear wheel in a vice ever shot.
 
does it make that dinging sound when you do have the rubber cushers installed and everything tightened up?
 
Just experienced this myself while putting my bike together.
What you may have there is the 2 bolts which hold the brake shoes on the back plate hitting the paddle rivets on the drum.
Check the bolts for a grinding mark and also the rivets.
 
gtsun said:
Boring?? How could you possibly think we would find that boring. That was without a doubt the most exciting film of a rear wheel in a vice ever shot.
Click to expand...

I'm gonna bookmark that and send it to all my friends on Facebook.
 
That looks to me like one seriously out of balance drum. Is it an OEM? Jim
 
Had to test a camera, and see if I could post it, so I gave it a shot and tested it on you understanding lot..
No brake shoes fitted. The "noise" is the paddles hitting the walls of the recesses where the cush rubber normally sit (not fitted now). Do think it is OEM, it shows number 06 2194 and date 25-7-73 in the casting.
 
It looks like finding the heavy spot will be easy. A little work with a drill bit or grinder and you could probably get it fairly close just rotating it on its center.
It would sure make it tough to balance a tire with it that far out. Jim
 
Jim, yep, should be easy fix.
Am actually not surprised, it's a casting, I see no machining to the effect of balancing.

I find the drum quite wobbly around the dummy axle, have to look into that too.

Also noticed the "brake cam bearing and stay" thingy, where the spring slings around, does not align nicely. It is ok when I move the shim that is normally on the inside of the brake plate (at least that is how it shows in the part list diagram) to the outside, so under the thick spacer. Should it be like that?
 
slimslowslider said:
Jim, yep, should be easy fix.
Am actually not surprised, it's a casting, I see no machining to the effect of balancing.

I find the drum quite wobbly around the dummy axle, have to look into that too.

Also noticed the "brake cam bearing and stay" thingy, where the spring slings around, does not align nicely. It is ok when I move the shim that is normally on the inside of the brake plate (at least that is how it shows in the part list diagram) to the outside, so under the thick spacer. Should it be like that?
Click to expand...

Wobbly on the dummy axle is fine, that's as designed. It relies on the adjacent bearing in the wheel hub to be pulled tight up against it with the main axle.
 
slimslowslider said:
Jim, yep, should be easy fix.
Am actually not surprised, it's a casting, I see no machining to the effect of balancing.

I find the drum quite wobbly around the dummy axle, have to look into that too.

Also noticed the "brake cam bearing and stay" thingy, where the spring slings around, does not align nicely. It is ok when I move the shim that is normally on the inside of the brake plate (at least that is how it shows in the part list diagram) to the outside, so under the thick spacer. Should it be like that?
Click to expand...

I don't know off the top of my head, but I have a couple virgin wheels with the brakes in them. I will take a look in the AM. Jim
 
Balancing the brake drum is not to hard to do if you have a static wheel balance stand.
Gut the drum and install the two-row bearing---no grease--just maybe some WD40 for lube and spin the drum--find the heavy zone and add weight to counter balance and the see how much weight it took---grind off material to match weight and done.
 
Here the wobbly drum, with wheel and everything bolted up. Looks not normal to me, considering there is / should be a double row bearing in there.

[video]http://www.youtube.com/watch?feature=player_detailpage&v=tPiCb0odhLQ#t=5s[/video]
 
It's got to be worth replacing the bearing?
are you sure the whole assembly is complete with all spacers, washers, felt grease retainers and (crucially) circlips present?
It has to be worth comparing what you have to the Workshop Manual
 
Wow-ed out races, bad axle, blown bearing, missing parts, wrong dummy axle, etc,etc,etc.
 
Just got it all apart, and the culprit was the bearing allright.
All the right parts were in there.
The wear could not be heard at all when turning the drum, it ran so smooth. Oh, and a very tiny bit of play between outer race of bearing and drum housing, the circlip will not hold it square, alas, Loctite or equivalent might help out here.
The bearing at first didn't budge, despite some moderate heat and a lot of force from a puller.
It appeared a really small ridge had built itself at the edge of the groove for the circlip, but is was enough to prevent the bearing from moving out any further...
Dremeled the ridge away. The bearing is RHP, bronze cage and all.
Now back to the unbalance, back to the grinder, one of my favourite tools... :wink:
 
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