G50 front brake adjustment

Information relating to the Matchless G85 500cc Heavyweight, AJS 7R, Matchless G45 and Matchless G50
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Duncan_G50
Posts: 3
Joined: Thu May 15, 2014 12:33 am
Location: Sydney, Australia

G50 front brake adjustment

Post by Duncan_G50 »

Some advice from the Team requested...

I'm having problems adjusting the TLS front brake on my G50. Í recently had the shoes re-lined, and braking is now woeful! The shoes have been lapped in, but there are still no scuff marks on the leading and trailing edges, only the central parts of the shoes - probably about 40% of the contact area. I suspect the rod between the cam levers needs adjusting, but I have no idea how to do this. Any advice on setting up a TLS would be greatly appreciated.

The bike is únmolested (number 1874) with original brakes. I bought the bike in South Africa in 1977, and would love to know more about it's history. Is there any way of finding out how many 1962 G50's were exported?

Thanks,
Duncan
(Sydney, Aus)
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Rob Harknett
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Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: G50 front brake adjustment

Post by Rob Harknett »

Ashampoo_Snap_2014.05.15_06h01m29s_002_.png
Looks like you have done OK so far relined & turned linings, ( has lapping achieved this ) now adjust rods.
But the instruction book does not say how.
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iansoady
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Location: Hall Green, Birmingham

Re: G50 front brake adjustment

Post by iansoady »

If the wear is only on the central part of the linings, it indicates that the radius of the drum is bigger than the effective radius of the shoes when the brake is applied. I don't know the specifics of the G50, never having aspired to such exotica, but usually with TLS there is a link rod which needs to be adjusted so that the leading edges contact the drum at the same time. On some bikes this rod had one end with a LH thread and the other RH so that turning the rod changed its effective length.

But as I can't get a decent front brake on my G80 I wouldn't listen to me!
Ian
1931 Sunbeam Model 10
1999 Honda SLR650
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Rob Harknett
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Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: G50 front brake adjustment

Post by Rob Harknett »

Seems lapping did not get the linning's rad the same as the drum. I once had some linings that looked bumpy.
Having no workshop tools, to save what could had been a long bedding in process, I cut a strip of 180 sand paper, then stuck in in the drum with twin stick. You could see high spots after a few rubs of the shoe in the drum. Finished off with something like 220 wet & dry, bevelled leading edges etc. Cleaned drum and shoes of sanding dust before fitting with the garden hose pipe.

I have a Suzuki front wheel in my mod 14 CSR that has rods to adjust. Dam good brake, except it shoots my pillion forward and me up on the tank. Even though the lightweight would only do about 60,I once forgot and slamed the brake on. Scary, Jan was not ready for it, I got shoved up on the tank, my knees ended up almost under the handlebars.
242017
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Joined: Mon Jan 01, 1990 12:00 am
Location: HASLEV 4690 DENMARK

Re: G50 front brake adjustment

Post by 242017 »

I suspect that your linings,together fitted to the back plate need to be put on a lathe and turned until they are 100% cylindrical.
I race with my G85cs and when the linings have been changed they are Never 100% round anymore. and need to be turned down until the brake linings shows signs of being freshly machined all over......Then you can adjust them to run in the hub
Duncan_G50
Posts: 3
Joined: Thu May 15, 2014 12:33 am
Location: Sydney, Australia

Re: G50 front brake adjustment

Post by Duncan_G50 »

I am quietly kicking myself. I was so focussed on the link adjuster, I didn't even think of checking the shoes. (Not seeing the forest for trees...) A quick check with a caliper proved that the high spots are in the centres. So much for the high $ job done by the reputable brake shop!

So, it's going to be a case of some light 220 sanding on the glazed spots; refit the wheel; run the brake lightly until it just contacts; remove wheel; check and repeat... It's going to be a slow process, but I want to get it right. I'll also have an excuse to do the odd road test - just to irk my neighbours... I have used the sandpaper-glued-to-drum trick before, but it's not that accurate. Because the brake assembly floats very slightly on the axle, the sandpaper can remove some brake lining from the low spots as well.

Then, when I have an even contact area, I should be able to adjust the link rod to get the lower half of second shoe making contact. Or, would it be best to lock the adjusting rod in at the closest position, and then trim the shoes accordingly?

Many thanks!
242017
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Joined: Mon Jan 01, 1990 12:00 am
Location: HASLEV 4690 DENMARK

Re: G50 front brake adjustment

Post by 242017 »

The only accurate way to do this is on a Lathe.
The brake shop only glue the brake material on and give them a "rough" radius.
Sandpaper is really a "no no" you cant see what you are doing after the first pass with sandpaper....Do it properly
Will_AJS7R
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Joined: Fri May 16, 2014 5:15 pm
Location: UK

Re: G50 front brake adjustment

Post by Will_AJS7R »

From memory of something I read long ago.
Never adjust the rod after machining assembled linings.
As I remember it the procedure is something like this. The brake cam levers should be parallel. Oversize linings should be fitted to the shoes and assembled on the brake plate. At this point insert a .020" ( half millimetre ) thick spacer between the brake cams and the shoes to simulate the position when the brake is applied. Only then, use a lathe to machine the linings to the diameter of the brake drum. When the spacers are removed the assembly should now fit in the brake drum with minimal movement to contact the drum. It is essential to back off the leading edges of the linings. It is advisable to deglaze the drum lightly with some emery cloth if it has seen a fair bit of use. Please feel free to correct me if any of this is nonsense.
242017
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Joined: Mon Jan 01, 1990 12:00 am
Location: HASLEV 4690 DENMARK

Re: G50 front brake adjustment

Post by 242017 »

Sounds about right....the linings must be cylindrical before trying to adjust them
Duncan_G50
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Joined: Thu May 15, 2014 12:33 am
Location: Sydney, Australia

Re: G50 front brake adjustment

Post by Duncan_G50 »

Agreed, there's no point in trying a bodge job... It will be best to have the shoes re-lined, and then trimmed in a lathe. Thanks for the tip about the cam/shoe clearance, Will. The helpful advice from all is appreciated...
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