A50 braking problem

[Drummie]

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

[idie]

Have you got a chamfer on the end of the brake linings.

[Drummie]

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.

[Spaceman]

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.

[Mike Farmer]

 

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

[DAVE BRADY]

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.

[Drummie]

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.

[Drummie]

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

[idie]

Don;t sand the linings. Just chamfer the ends back about 1/4 inch, thay's all you need.

[DAVE BRADY]

Hi,

Something like this.

Dave.

[Spaceman]

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.

[JulianS]

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

[Spaceman]

I would agree about the ridge which should not be happening! As said, there appears to be an alignment problem within the drum.

[Drummie]

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.

[Spaceman]

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.