1954 G80 Rear Brake Problem

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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1954 G80 Rear Brake Problem

Postby mrpjhancock » Sat Oct 13, 2018 4:26 pm

Hi. I have a problem with the rear brake on my 1954 G80. When I spin the wheel there is a scraping sound. I took the wheel off and inspected the brake. The problem is when the brake cam rotates it moves the brake shoes away from the back plate and after a couple of brake applications it touches the drum and that creates the noise. I have replaced the brake cam and it is a good fit in the hole through the back plate . . . . no excessive play. Has anyone come across this before ?
I have attached photos showing the brake assembly and before and after photos
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Re: 1954 G80 Rear Brake Problem

Postby Winkie » Sat Oct 13, 2018 5:00 pm

I had a similar problem with my front brake. It was caused by the pivot pin being loose, which allowed the shoes to move about.

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Re: 1954 G80 Rear Brake Problem

Postby Mick D » Sat Oct 13, 2018 5:03 pm

Hi

Try fitting the retraction springs from the other side of the shoes.

Regards Mick

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Re: 1954 G80 Rear Brake Problem

Postby alanengineer » Sat Oct 13, 2018 5:18 pm

Try adjusting the brake plate a bit further away from the hub, probably only needs a turn

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Re: 1954 G80 Rear Brake Problem

Postby ajscomboman » Sat Oct 13, 2018 5:42 pm

alanengineer wrote:Try adjusting the brake plate a bit further away from the hub, probably only needs a turn


It's a rear brake Alan, not adjustable like the front.

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Re: 1954 G80 Rear Brake Problem

Postby mrpjhancock » Sat Oct 13, 2018 5:54 pm

Hi chaps . . . . just tried changing the springs to the top side and the pivot pin is solid . . . . . No difference :(

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Re: 1954 G80 Rear Brake Problem

Postby Pharisee » Sat Oct 13, 2018 7:12 pm

Are the thrust pads worn and driving the shoes up as the cam bears on them?

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Re: 1954 G80 Rear Brake Problem

Postby alanengineer » Sat Oct 13, 2018 7:38 pm

I have just replaced some brake shoes and used new or remanufactured ones. They were painted gold also. I had to do some interesting filing to get them to fit. I wonder if that is your problem also. Not the same problem as mine, but quality control. Maybe, the shoes are too wide and just need a good file to fit.
Your photo shows the scraping on the shoes, how about a photo of what the shoes are scraping on.

Apart from putting new shoes and springs in, have you done anything else that might be relevant.
Maybe silly, and its your time, try putting the springs in the other way round.

AJScomboman, good point, forgot that bit!

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Re: 1954 G80 Rear Brake Problem

Postby mrpjhancock » Sat Oct 13, 2018 8:00 pm

Iv tried the spring thing with no luck . . . . I was at the AMOC parts shop today and tried exchanging my brake shoes for some new ones. Unfortunately my shoes werent good enough to exchange. Apparently they need to be in perfect condition!
So Im stuck with the ones I have
I have attached a photo of the brake drum its self. looks like its the hardened pads that are coming into contact
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Re: 1954 G80 Rear Brake Problem

Postby alanengineer » Sat Oct 13, 2018 8:07 pm

Is that a new brake drum

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