Rather useless brakes

Information relating to the Matchless G5 or AJS Model 8 350cc Lightweight
Steve S
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Rather useless brakes

Post by Steve S »

Hi all, getting near to MOT time and am not at all sure the brakes on my Lightweight are good enough.

Just fitted new shoes from club spares, although the old ones weren't that worn, and they are not very impressive, the brakes that is.

Drums look OK, but the levers appear to be worn creating some play in their fitment to the expanders. Have fitted some sheet metal shims to the front shoes but still the adjuster is near to maximum.

The angle of each lever is 90 degrees to the cable/rod. Turning the levers around doesn't help as the slots are not at an angle.

Can you fit a different lever from another model?

Any ideas please.

Steve S.
SPRIDDLER
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Re: Rather useless brakes

Post by SPRIDDLER »

Firstly I would say that new shoes will take a while to bed in so that their profile becomes a better match with your drum profile. Today's non-asbestos linings seem to be harder and less effective than the original material. (Soft(er) linings are available from companies such as Saftek).
Second, maybe your adjuster is nearly at its full extent due to you having a wrong cable....? i.e. too short an outer or too long an inner? Perhaps the cable is for a h/bar lever with an adjuster at the lever end and your lever doesn't have an adjuster....?

I guess the L/W brake is near enough the same as for my H/W. If so there's a brief compilation below of posts which I put on the Forum back in 2009 which may give you some food for thought, clues, or may even help., Even if the L/W isn't exactly the same the principles are generic to most if not all single leading shoe assemblies.
The whole original thread and various comments and Q&A's can be found here:

http://www.jampot.com/forum/viewtopic.p ... mprovement



Anyway here are my thoughts from 2009.....

Whilst I had the wheel out to do some serviceing I took the opportunity to photo the mod which I made 6 months ago to the front brake lining on my '54 G3LS.

Two pics:

1. Showing which is the Leading and which is the Trailing shoe. Arrows indicate direction of wheel rotation. Leading edge of leading shoe ('L') is adjacent to cam.:
100_1398 (640x480).jpg

2. Chalked area of lining removed:
100_1399 (640x480).jpg

When you have the brake shoes assembly out of the wheel chalk an arrow on each brake shoe in the direction of wheel rotation. Be careful when marking the arrows as you'll be looking at the brake assembly 'back to front' i.e as a mirror image of when it's installed.
The arrow pointing away from the brake cam/expander is on the leading shoe and the arrow pointing towards the cam is on the trailing shoe.
The leading edge of the leading shoe is at the cam end of that shoe. The trailing edge of the the trailing shoe is also at the cam end, but of the trailing shoe.
Because the fixed brake shoe pivot doesn't move when the brake is operated the cam ends of the shoes touch the drum first.
If the trailing edge of the trailing shoe touches before the leading edge of the leading shoe (keep up at the back) you lose the 'servo' effect of the drum 'dragging' the leading edge of the leading shoe outwards towards the drum.
If you can follow all this rambling (!) you can visualise that the trailing edge of the trailing shoe is being 'pushed' inwards away from the drum when the brake is applied.
Furthermore, you also want as much area (length) as possible of both linings to contact the drum. Once one shoe (either shoe) has contacted the drum the cam will not turn any more therefore you want to ensure that it is the leading shoe which makes contact first.

To give an extreme example you could remove either shoe completely, refit the assembly, and the brake would still work, after a fashion. (Although it would not be possible to fit the pull-off springs).
This diatribe is only relevant to single leading shoe assemblies of course as a twin leading shoe (TLS) brake has two operating cams (one at each end of the shoes) and no fixed pivot, so both shoes are leading shoes.........
O.K, you can go now.

-----------------------------------------

I put the shoe in a vice, hacksawed through the 7/8" width of the lining then used a chisel to carefully 'lever' or slice off the lining material (starting from the cut and going towards the end of the linings as you don't want to risk disturbing the lining that's to remain).
I would imagine that removing just say half the thickness would be o.k. - enough to keep it clear of the drum.
Only tried it bonded linings though.

Later:
It's worth repeating that centralising the shoes on the fixed pivot and on the brake backplate after refitting the assembly to the wheel is essential, as is having the arm to inner cable angle close to 90 deg at the point when the shoes contact the drum.
Handlebar lever should have 7/8" distance between lever pivot bolt and cable nipple; many pattern levers are 1" which means that they will require a significant amount more effort at the lever (than a 7/8" one) to obtain the same force at the shoes.
I also fitted a heavier duty cable as I found that the existing pattern cable had a flimsy outer (the 'conduit') which squashed/compressed when braking giving a very spongy feel to the lever.

------------------------------------


I had been researching both the theory and bar room waffle (which is the leading or trailing shoe?.. so forth) behind this mod for some time. However, ignoring the long-winded science/physics involved I can only say that my practical experience is that it's worth doing: Better initial 'bite' without grabbing, more powerful retardation with less strength needed in the hand and fingers thus reducing fatigue/cramp on long hilly rides.
It goes without saying that the brake needs to be correctly set up as well - i.e. the lower brake actuating lever should be at the most advantageous angle (i.e. 90 deg) to the cable at the point when the shoes contact the drum, fixed pivot loosened then tightened after reassembling brake into drum and with the brake applied, shoes/backplate centralised (i.e. brake applied) before tightening the backplate locknut, and the cable run without sharp bends etc. etc. The centre of the lever nipple to pivot bolt distance should be 7/8" and no greater.
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Last edited by SPRIDDLER on Sun Aug 13, 2017 7:02 pm, edited 2 times in total.
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Expat
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Re: Rather useless brakes

Post by Expat »

Hi Steve,

SPRIDDLER'S idea is definitely worth persevering with. I can personally vouch for the improved stopping power it provides after applying it to my G3 brakes. Just gotta get the old brain cells around the theory, never my strong point. :D :D

Regards, Steve
Keep shiny side up.

These are my principles, if you don’t like them, I have others. (Groucho Marx)
56G80S
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Re: Rather useless brakes

Post by 56G80S »

Have also done this in fact following Sprid's original post, although not as vigourously as him, and there was an improvement that made it worthwhile. Next time I have the brake plate out I'll be more aggressive with the mod.

Echo the centralisation point.

Johnny B
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Re: Rather useless brakes

Post by SPRIDDLER »

I think as Steve and John have rightly said, 'it's worthwhile'. I wouldn't want to give the impression that it transforms performance but when you don't have much to start with it pays to make the most of what is available......... :oops:
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Rob Harknett
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Re: Rather useless brakes

Post by Rob Harknett »

I have not read all, as there is quite a lot to read. So here's what I do, to get the lever in the correct position, I use a thick washer each side. If the plate won't go in the drum, go a bit thinner with the washers. I file the leading edge angle. Bit of tin stops damage to the shoe. No risk of damage to shoe or fingers a chisel would do. Give the drum and linings a real good clean, Vim powder or oven cleaner is good as it is a bit abrasive. It should clean also take off the shin. When correctly fitted they may need a lot of bedding in. Ride round the block with the brake on, you may have to do this a few times, perhaps also another clean. Probably due to the drum oil soaked or rusty metal making them dirty again. This could take ages so you give up, don't. Even if you get the brake working a bit, still do the riding with brake on each time you go for a run out. Eventually you will get the brake to lock the wheel. But after a lay up, you have to ride with brake on until it starts to bite.
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Ozmadman
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Re: Rather useless brakes

Post by Ozmadman »

I thought that my Lightweight brakes (both of them ) were one step better than useless especially compared to my 1974 RD250 which was the 1st of the models (US spec) to have a hydraulic front disc brake but my M.O.T guy who tests lots of classic bikes and scooters said that the brakes weren't too bad for a 1960 bike and that he can only test them based on the standards back then. If he used today's criteria it would fail miserably, his advice .... keep your distance, a lot of distance cos you won't stop in a hurry..
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
Steve S
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Re: Rather useless brakes

Post by Steve S »

Thanks everyone for the very useful advice as always.

Have ordered some cable stop ends that fit over the cable at the handlebar end and act as an outer extension rather like an adjuster. My levers are 6 mm internal diameter so won't accept an adjuster.

I will then run around for a bit with the brakes being applied and see whether it improves matters. I knew I would have to ride very defensively as I have strong memories of pathetic brakes in the 60s and 70s!

Steve S.
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Rob Harknett
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Re: Rather useless brakes

Post by Rob Harknett »

I am sure you will find running about with brakes applied will speed up bedding in process. Works for me. But may need a few runs. Which is better than having to do 500 miles plus to bed them in. I believe that's why some people think their brakes are no good. As it will take ages to clock up 500+ miles to bed brakes in. In particular if long gaps between runs, the linings and drums getting dirty/rusty again. So they never really get brakes working right. I do not run my bikes much also have more than one. So I always ride with brake on each time I go out, until they start to bite.
JohnHewes
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Re: Rather useless brakes

Post by JohnHewes »

Dear Ozmadman, you are a lucky man. My G3 has failed the MOT as there was more than 10%variation in braking effect as the wheel turned, and the tester insisted that the he bike had to confirm to current standards. I know they will lock the wheel in an emergency, must stop looking at girls when behind a Jaguar, still I didn't hit it!
Was he right?
John
Locked