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Rear brake issues

stu

Veteran Member
Joined
Mar 13, 2024
Total Posts
148
Total likes
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Location
Toronto ON Canada
Ok..would love to know what I did wrong here. 69 450 K2. I get nothing when I apply rear brake pedal to stop wheel. As a matter of fact, it only seems to slow or stop when I apply upward pressure on the pedal? Clearly, I'm in the matrix.

 
The clunking sound when you apply the brake seems to indicate that the brake pedal is hitting the frame. The piece that the brake rod connects to -the part beside the number 3 below. If you have no more adjustment it could be the brake shoes need replacing.
You could also make sure the actuating arm on the brake panel is lined up correctly - there should be a punch on the arm and another punch mark on the brake cam.

1738439437944.png
 
Do you have these dots aligned? If the lever is on the shaft in too far one way or the other, it will affect the brake rod adjustment and you won't have enough pedal travel ditance to make the shoes contact the drum

1738439973019.png

Also, did you arc the shoes to the drum? If not they probably won't stop very well at first, possibly very poorly until they wear in.
 
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Do you have these dots aligned? If the lever is on the shaft in too far one way or the other, it will affect the brake rod adjustment and you won't have enough pedal travel ditance to make the shoes contact the drum

View attachment 42237

Also, did you arc the shoes to the drum? If not they probably won't stop very well at first, possibly very poorly until they wear in.
Dots are aligned, yes. Not sure about the shoes being arced as they were done by the same guy who trued my wheel.
 
Dots are aligned, yes. Not sure about the shoes being arced as they were done by the same guy who trued my wheel.
I'd ask, but I'd also doubt it was done because not many realize how far off the fit is on most new shoes these days.
 
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The clunking sound when you apply the brake seems to indicate that the brake pedal is hitting the frame. The piece that the brake rod connects to -the part beside the number 3 below. If you have no more adjustment it could be the brake shoes need replacing.
You could also make sure the actuating arm on the brake panel is lined up correctly - there should be a punch on the arm and another punch mark on the brake cam.

View attachment 42236
Dots are aligned on the actuating arm, yes. Will check shoes and connector..thanks!
 
Since it appears you have almost zero braking action when pressing the pedal, I would tighten the adjuster nut until you feel some braking action. Even if the shoes where not arc'ed you should still be able to stop a spinning wheel with just the high spots on the shoes.
 
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How important is the alignment of those punch marks? Seems that indexing the arm forward one or two teeth on the spline could be helpful. There appears to already be a good bit of the adjusting rod threads exposed and the spring is already fairly compressed.
 
How important is the alignment of those punch marks? Seems that indexing the arm forward one or two teeth on the spline could be helpful. There appears to already be a good bit of the adjusting rod threads exposed and the spring is already fairly compressed.
If you have to clock the arm to get better shoe contact something is wrong with the setup. Either the brake shoes are too worn, or the incorrect ones installed or something internally is off on the brake plate.
A shot of the alignment of the dots, plus if there is a inside shot of the brake plate with the shoes installed would be helpful. A further tightening of the nut may help as Boddy noted, yet it should be making decent contact within a few more turns if it is going to help.
 
Here's something to look at since I just compared you brake arm to two bike pictures I have and your brake arm is more rearward vs a CM450A model and a CB450SC model. So I suspect that is part of the issue where your getting no contact or very little brake shoe action. Did you have the brake plate apart and the splined shaft out for any reason previously?
You may need to take the brake plate apart and re-clock the splined shaft 180 degrees as a spit ball guess. I seem to recall having to change the shaft position on builds in the past. Yet no memory to say why?? :unsure:


CB450SC

P1100033.JPG

CM450A

P1050379.JPG
 
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Here is a shot of my '71 CB450 for the angle of the brake arm. I don't have punch marks for the alignment but rather an area on the arm and the brake cam where there are no splines. I could have rotated the arm one more spline to the 8 o'clock position to give more adjustment but I'm good with it the way it is.
20241010_160159.jpg
 
Def tighten the adjuster nut. I have very little travel on my brake arm. When riding, you don't want that much movement in the brake arm... at least I don't
 
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