Front brake assembly

Information relating to the Matchless G12 or AJS Model 31 650cc twin
Mollbhan
Posts: 109
Joined: Sat Apr 06, 2019 11:52 pm
Location: Perthshire UK

Front brake assembly

Post by Mollbhan »

Help needed please, when I push my 1961 G 12 backwards the front brake makes an appalling scraping sound and the brake plate can be seen to vibrate, it will sometimes do this when pushing forwards, question is, should the big nut with the two flat sides be screwed hard back up against the brake plate or should it be just clear as it is at the moment. The brake works perfectly well but something is not right. Having sold my last Matchless in 1967 I am a bit rusty with AMC bikes.
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: Front brake assembly

Post by SPRIDDLER »

The brake plate should be locked between the inner nut and the outer nut.........refer to your Owners Manual:
http://archives.jampot.dk/book/Owners_manuals/
Brake cover plate.JPG
You do not have the required permissions to view the files attached to this post.
'There is a tide in the affairs of men
Which taken at the flood............'
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Front brake assembly

Post by Mick D »

Hi

As Sprid points out, the brake plate should be pinched between the inner and outer nuts - you'll need to take the wheel off to set the position of the inner nut. Look on the bright side, at least you'll then know the PO had fitted the inner nut ;)

Regards Mick
Mollbhan
Posts: 109
Joined: Sat Apr 06, 2019 11:52 pm
Location: Perthshire UK

Re: Front brake assembly

Post by Mollbhan »

Thanks Spriddler and Mick the set up makes sense now, the workshop manual I have is extremely vague on the subject and I was completely unaware of jampots online manuals, a wealth of reading there.
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: Front brake assembly

Post by SPRIDDLER »

Mollbhan wrote:I was completely unaware of jampots online manuals, a wealth of reading there.
That was a link to a specific manual from the sub index under 'Books'. Much more on the main page here:

http://archives.jampot.dk/
'There is a tide in the affairs of men
Which taken at the flood............'
User avatar
AJS 500
Posts: 38
Joined: Wed Aug 05, 2015 5:27 pm
Location: KENT UK

Re: Front brake assembly

Post by AJS 500 »

Just to put my 2 bobs worth in.
I've found no matter how much I clamp the plate as described it manages to work loose. Found this on my g12 and my G80 front brakes. My solution was to measure the distance between the outer hub and brake plate with the internal nut clamped to the bearing assembly and outer plate nut tightened down then machine a spacer to take up the gap so the other plate sits flush with the outer drum edge. This came to approx 1.2mm on my g12, just over 40 thou.
Once fitted and tightened I've had no more problems on either machine.
Hope this helps
Clive.



Sent from my iPad using Tapatalk
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Front brake assembly

Post by Mick D »

AJS 500 wrote:My solution was to measure the distance between the outer hub and brake plate with the internal nut clamped to the bearing assembly
Hi Clive

Have I misunderstood your description or have you tightened the inner nut onto the bearing grease cap? If the latter I think you have clamped a rotating part, (the grease cap), to a non-rotating part, the inner nut. You could be chewing up your hubs.
Brake Nut.png
Regards Mick
You do not have the required permissions to view the files attached to this post.
User avatar
Rob Harknett
Member
Posts: 11236
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Front brake assembly

Post by Rob Harknett »

I have always done this on a trail and error basis. By, adjusting the inner nut, try the brake plate on. Do this until you see the plate looks about right. Plate lip outer edge about level with the hub otter edge. Then lock it up nice and tight. If there's any binding perhaps due to plate warped a bit or what ever, you know which way you need to go perhaps half a turn on the inner nut. It can be a bit fiddly, but once I have been satisfied its OK, its stayed put until I next have to have it apart.
raffles
Member
Posts: 609
Joined: Mon Jan 01, 1990 12:00 am
Location: NORTHAMPTONSHIRE UK

Re: Front brake assembly

Post by raffles »

What MUST be done____ set it up in a vice spin the wheel and with a ring spanner on the brake arm nut
lock the brake on tighten the outside nut fully before you release the brake this centralises the brake
I have never in 40 years of AMC ownership and many thousands of miles had a brake plate work loose
Tony
User avatar
clive
Member
Posts: 5657
Joined: Mon Jan 01, 1990 12:00 am
Location: LONDON UK

Re: Front brake assembly

Post by clive »

I agree with your method Tony but I can only manage 40 years AMC ownership by the end of the year! Its probably the one thing, and in travelling to work daily that didn't go wrong.
clive
if it ain't broke don't fix
Locked