Hi all, I have a 1966 a50 and at present i have a problem with the rear brake. The brake was snapping on so I removed the rear drum,in the off chance the lining/linings had separated from the shoes. It hadn't. I then took the bike for a run and the brake was ok but after about 6 miles on applying the rear brake there was a crunching noise, sounding very much like attempting to select a gear without using the clutch. Now after loosening the brake off a bit I'm back to it snapping on again. I'm wondering if anyone has had anything similar and if they managed to solve the issue. Thanks in advance. Drummie
Have you got a chamfer on the end of the brake linings.
That's been mentioned to me. The shoes were fitted before I bought the bike and if I'm honest, i didn't check when I had the drum off.
Assuming the brake cam pivot is not excessively worn in the brake plate and the linings are chamfered, the snatch experienced must be due to excessive friction between the lining and brake drum. You can get this effect if the brake drum is badly rusted, badly pitted or is oval. If not the brake drum then it may be the condition of the linings although when they deteriorate they normally cause the opposite problem.
:) :) :) :)
Is your brake actually going completely off when you take your foot off the pedal. Not possibly "catching" which would cause friction and heat build up. We had a similar problem and cured it by putting a serious return spring half way along the rod. It cured problem.
Mike 8) 8) 8) 8)
Hi,
Is it possible that you have shoes that are one leading and one trailing rather than both being the same and they are the wrong way round?
Dave.
Thanks Guys for all your help. I'm going to strip it down today and see what's going on and I'll be back to report what I find. Thanks again.
Hi again, here's what i found. The shoe linings haven't been chamfered, hopefully the photos are clear enough to see. My question now is, do i sand/file the linings or am i going to make things worse. Thanks Drummie
Don;t sand the linings. Just chamfer the ends back about 1/4 inch, thay's all you need.
Hi,
Something like this.
Dave.
It's difficult to tell from the pics but the linings look a bit contaminated and one has a curious score along one side. I would definitely give them a slight sand to remove any surface contamination.
I think the ridge on the linings is caused by the shoe sticking out a bit past the edge of the drum, and that bit of the lining not wearing like the rest of the surface.
The lining in the second photo looks like it is getting thin, probably the leading shoe which tend to wear a bit more than the trailing.
If it was my bike I would check alignment of the shoes on the brake plate and in the drum and would replace the shoes
I would agree about the ridge which should not be happening! As said, there appears to be an alignment problem within the drum.
Thanks everyone for the help. I've built it back up having cleaned the shoes and drum. I've taken another couple of photos showing the brake pedal and how far it travels, before it starts to engage, yet it's almost fully adjusted. The shoes look worn but not as bad as to fail to make contact with the drum. I'm very puzzled.
It would be interesting to see the angle at the brake drum lever. Ideally, this should almost be at right angles to the brake rod when fully applied and definitely doesn't want to be further forward than that. If it is, it might be worth seeing whether you can re-position it further back on the the brake cam spindle to improve the angle at which the brake bites.
Hi Spaceman, this is the brake lever position when not being pressed.
That looks a bit more forward than mine but it is the angle it makes with the brake fully applied that is critical - in other words, how far forward does the lever move when you put your foot hard on the brake pedal? If it doesn't get past being perpendicular to the brake rod then, from a brake operating efficiency point of view, that looks ok. Problem then is that you appear to have run out of adjustment on the brake rod leaving you with too much foot pedal movement (my brake rod has much more adjustment range on it). If you can't correct this by repositioning the brake lever on the brake cam spindle, the only solution would be new brake shoes.
Having said all that, it is difficult to see how the brake adjustment has anything to do with your original problem. Out of interest, what was the line shown on one of the original brake lining pictures - was it a wear ridge and, if so, what was causing it?
Hi again Spaceman, it's like the brake needs adjusted but already is. There was no evidence of what caused the score on the lining. I'm going to post a photo tomorrow of the lever at the hub with the brake fully on and if i can get your opinion it will be much appreciated. Drummie
Hi, this is a photo with the brake pedal pressed down fully.
The angle looks ok but is there enough adjustment left on the brake rod to produce the right amount of movement at the foot pedal?.
I'm thinking new shoes to start with and see where it goes from there. Thanks for all the help, I'll post the outcome. Drummie
A quick update on the braking problem. I changed the shoe round on the hub (not too sure this was the problem). I also think the hub may not have been seated properly. The brake now works but still has a lot of play at the pedal, although the shoes are adjusted to just before binding. So still scratching my head on that one.
The problem may simply be that the linings are too worn and, when you apply the brakes, the leading edge of the leading shoe bites or makes contact with the drum initially but it then takes excessive brake movement to cause the rest of brake shoe linings to be pressed against the drum. I would definitely check the drum for ovality but new shoes are probably the answer.
Hi Spaceman, I'll fit new shoes and see how it goes Thanks for your help. Drummie
I would have thought ovality would cause some pulsing of the pedal.
I would just fit some new shoes and accept a fair amount of pedal travel until they bed in a little.
I must say my A50 has a fair amount of travel on the pedal to avoid any binding or rubbing.
Hi all,
Just an update on my rear brake problem. I chamfered the brake shoes and cleaned up the drum but I believe the problem may of been the hub lining up correctly with the swinging arm. Having had the wheel off and on again a number of times, I realised it was sitting slightly different. On inspection it was seated differently ie properly. So now I have a great bike with a useable rear brake, Anyway I just thought an update would maybe help anyone with similar problems and to let all those who helped me know the fault. Once again thanks for you help. Its a great sight this.