Author Topic: Why is my front brake still useless?  (Read 1500 times)

Online JulianS

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Re: Why is my front brake still useless?
« Reply #60 on: 31.01. 2019 17:46 »
The post 1960 A10 cable operated rear brake with brake plate lever pointing down is a case where the cam contact edge is closer to the pivot and operates the same as the reversed levers discussed. Most of us will acknowledge that it is still a pretty mediocre brake despite the "reverse" lever. So the reverse lever is not a panacea.

If the lining is not compatible with the rest of the brake and the intended use of the bike then whatever you do to the levers will not rectify the problem. I suspect that if you were to enquire of the supplier of the complete lined shoe  he would not be able to tell you the properties of the lining, how quickly it wears or how its coefficient of friction varies with temperature.(the old and famous Ferodo asbestos based moulded AM4 green racing lining needed to be hot to work properly and was reputed to squeal and wear quickly)

In times when the likes of Ferodo  supplied a number of different materials suitable for bikes, sometimes to get the best results the old competition department would specify different material for leading and trailing shoe, or even two materials on one shoe. Ferodo listed 2 different lining materials for the common 8 inch full width A10 brake.

Choice, or availabilty of an appropriate lining is essential for good braking. The problem being identifying suitable modern non asbestos linings  to replace the old asbestos and give comparable braking.

Online worntorn

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Re: Why is my front brake still useless?
« Reply #61 on: 31.01. 2019 18:46 »
Ive had very good results with the new Ferodo Linings supplied by Vintage Brake.
The new brakes seem to work just as well as the older Ferodo did when in good condition.

Offline RogerSB

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Re: Why is my front brake still useless?
« Reply #62 on: 31.01. 2019 19:33 »
The post 1960 A10 cable operated rear brake with brake plate lever pointing down is a case where the cam contact edge is closer to the pivot and operates the same as the reversed levers discussed. Most of us will acknowledge that it is still a pretty mediocre brake despite the "reverse" lever. So the reverse lever is not a panacea.
If the lining is not compatible with the rest of the brake and the intended use of the bike then whatever you do to the levers will not rectify the problem.

I agree with the above. My 1960 GF has the rear brake lever pointing down so front and rear cams operate on opposite lobes - but I suspect over such a short distance from each end of a cam to the other (not being an expert in either physics or mechanical engineering) that the difference in force applied by pulling on the lever is probably minimal. I'd sooner put my faith in good linings, brake drums and the self servo action.

All very interesting nevertheless.

1960 Golden Flash

Online mikeb

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Re: Why is my front brake still useless?
« Reply #63 on: 31.01. 2019 19:35 »
Glen - thats a good resource at vintage brakes. i might check them out. and re youtube 80mph stop on drum brakes - impressive, i had heard that vincent riders had a thing for sick teddy bears (tho not you RR!). pretty sure it was the back wheel locked and not the front.

Trevor - that's a good explanation, thanks

Dutch - is that some upmarket aussie thing these days: 'audi audi audi, oi oi oi!'
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Online worntorn

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Re: Why is my front brake still useless?
« Reply #64 on: 31.01. 2019 20:53 »
Mike, that's correct, the back wheel locked but note the front tire distortion with 30 psi in tire.
I try to avoid locking the front wheel as it's tough to stay upright when that happens.
This stop is with the front wheel just on the verge of locking.
Squeezing a bit harder on the front will lock it.
As it is this bike stops almost as quickly as my modern bikes.
The BSA with 2ls isnt far off either.

Glen

Online mikeb

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Re: Why is my front brake still useless?
« Reply #65 on: 31.01. 2019 22:22 »
Glen - oops - i hadn't noticed your name on the video - sorry about the bad taste teddy bear jokes *red*
it is a good amount of squish on the front tyre
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Online worntorn

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Re: Why is my front brake still useless?
« Reply #66 on: 01.02. 2019 00:01 »
No problem, as you can tell from the vid, I'm the king of bad taste!

Glen

Online duTch

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Re: Why is my front brake still useless?
« Reply #67 on: 01.02. 2019 09:33 »

 
Quote
.......Dutch - is that some upmarket aussie thing these days: 'audi audi audi, oi oi oi!'......

 Doesn't need much to upmarket that crap- one of the most moronic brain-deadening advertising campaigns I've ever seen....

 Glen- that Teddy almost remind me of the Brer Rabbit and the Tar Baby talking book that was on my local library when my young fella was little ( his mother worked there and brought home a stack every night)...we played the bit over and over when B.Bear and B.Fox were debating what to do, and B.Bear suggested- in slow southern drawl 'let's just smack him in the head'.... has to be audibly heard to appreciate.... (there's another bit of 'audi-audi' happening )    *eek*

 
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline paulmbsa

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Re: Why is my front brake still useless?
« Reply #68 on: 03.02. 2019 10:28 »
BSA Brakes work and very well set up right, when Alan cambell ran classic Brakes he was truly the Master he could make any brake work, he understood the mechanics physics and what linings did what, every brake he done was fantastic i still have a few left that he done unfortionatley like all masters of old trades he retired.
My point is you do not need to convert to tls,  you need a expert who understands brakes to set them up, unfortionatly now most just relign and give them back no really knowing much else. Alans alwas asked what bike is it and how do you ride and then used his experience to reline and set up correctly,

Online mikeb

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Re: Why is my front brake still useless?
« Reply #69 on: 04.02. 2019 07:49 »
Paul - i take your point. i went to a classic race meet in the weekend and asked half a dozen people about their 8" SLS set-up who had the brake arm rotation not reversed. most said they got someone else to do it for them. one or two described arcing the new shoes and how to do this. So i'm now figuring out how to, starting with the old fixed shoes as an experiment. also i've swapped the cam as it was binding a bit on one side.

as an aside, at the track about 50% of the 8" SLS front brakes (bsas, nortons..) had the brake arm rotation reversed, the other half not. I also talked to a knowledgeable guy in our local bsa club who said bsa published an article saying they didn't rotate the arm on road bikes due to increased leading shoe wear, only doing so for race bikes. I've yet to see the article and wonder if they always told the truth. but either way, i have more hope of getting a result.... eventually!
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Online mikeb

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Re: Why is my front brake still useless?
« Reply #70 on: 06.02. 2019 09:55 »
here's a bit of an update for any other brake sufferers.

i put the arm rotation back to 'normal' tho kept the homemade longer arm. and replaced the cam for one that held the shoes better.
i put the older fixed shoes back in (i don't know their history but still lots of meat), chalked them up and found little other than the bits of the trailing shoe were making good contact.
so i made an adjustable rod between the arm and the cable lug, set the shoes open the correct amount (smidgen under 8") and arced the linings in the lathe using a back axle and other bits to mount it. most came off the trailing shoe around its middle. I sanded a bit more off the cam side of the trailing shoe (which makes first contact).

and... its a lot better. not great, but it actually feels like a brake that I can rely on. still abs but i might even need to check the fork oil.

so. lessons for me - start with the basics before getting creative.
there's a low spot in the drum so i might work on that some day and maybe redo the chalk for a retest. but i've had enough brakes for a while.

and here's question - how to hold floating shoes in place so i can arc them on a lathe... any ideas?
New Zealand
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Offline Guy Wilson

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Why is my front brake still useless?
« Reply #71 on: 06.02. 2019 10:22 »
not directly related to Mike's post..a few years ago I bought a Landrover 109 that refused to stop on the front brakes (drum brakes) . I replaced the shoes, the pipes and still it wouldn't stop. Eventually, I spent a long time trying to work out how the brakes actually worked. The lightbulb came on when I realised the front hubs had been fitted on the wrong wheels, so what should have been a leading shoe was a trailing shoe...really obvious and easy once I realised, but I wouldn't have gotten there without getting in there and physically doing the stuff. There's plenty advice and theory about on how to fix stuff that lacks the practical.
What I appreciate about this forum is there's a lot of practical knowledge shared often by people who may have had to find out at some point the hard way and now have first hand knowledge of how to fix stuff...
My 8'' front brake should be working a lot better in the near future, having read this thread...
thank you chaps..
Guy

Offline BSA_54A10

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Re: Why is my front brake still useless?
« Reply #72 on: 07.02. 2019 22:16 »
here's a bit of an update for any other brake sufferers.

i put the arm rotation back to 'normal' tho kept the homemade longer arm. and replaced the cam for one that held the shoes better.
i put the older fixed shoes back in (i don't know their history but still lots of meat), chalked them up and found little other than the bits of the trailing shoe were making good contact.
so i made an adjustable rod between the arm and the cable lug, set the shoes open the correct amount (smidgen under 8") and arced the linings in the lathe using a back axle and other bits to mount it. most came off the trailing shoe around its middle. I sanded a bit more off the cam side of the trailing shoe (which makes first contact).

and... its a lot better. not great, but it actually feels like a brake that I can rely on. still abs but i might even need to check the fork oil.

so. lessons for me - start with the basics before getting creative.
there's a low spot in the drum so i might work on that some day and maybe redo the chalk for a retest. but i've had enough brakes for a while.

and here's question - how to hold floating shoes in place so i can arc them on a lathe... any ideas?

make a dummy backing plate.

The important thing is how far is the pivoting ends of your shoes off the drum ?
Shimming the shoes or making up a bigger pivot will make a massive difference.
Every one worries about how close the front of the shoe is and forgets about the back.
If it is measured in 10ths of inches it is too big.
Fitting longer levers is a waste of time.
You can not stop your bike using nothing more than your own grip strength applied over 4" to 6" of travel between you brake lever & handle bars.
You need a rapid pull to jamb the leading edge into the shoe to force the shoe into the drum using the kinetic energy of the drum, not the energy in your fingers.

Hydraulic brakes work differently because you can have up to 4000 psi at the slave cyinder.
Your hand would need a lever with 9' ( yes foot ) of travel to apply the same force.

To get the brakes to work you need the shoe really close to the drum AT BOTH ENDS.
Concentrate your efforts there & you will be rewarded with an excellent brake.
Frig around with longer levers and all you will do is pull off nipples and wear out pivot holes.
Bike Beesa
Trevor

Online worntorn

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Re: Why is my front brake still useless?
« Reply #73 on: 08.02. 2019 00:30 »
I don't use the lathe for doing the shoes these days.
I find it quicker to use the Emery and I get a better result.

Glen

Online KiwiGF

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Re: Why is my front brake still useless?
« Reply #74 on: 16.02. 2019 10:49 »
With the nz National Rally due next week I thought I’d fit a new tyre before setting off, then thought I’d might as well try to improve the crap rear brake while the wheels off. Although this is for a b31 I think it’s still relevant to A series. I used the sand glued to drum technique, and also 1mm spacer under the trailing shoe cam to ensure the leading shoe contacts the drum first. The tape i used is double sided car “moulding” tape which leaves a clear residue of sticky glue when the white backing is peeled off.

Bugger it, only a slight improvement! But it worked so so well on the front brake, WTF.

So I’m a bit like MikeB.....what to try next? Different lining material? Reduce lining length?

Anyway here’s some pics of the method. I got nearly 90% lining contact after sanding. It took 4 goes of sanding, cleaning the sandpaper and then re sanding, probably turning the circa wheel 20 times between the 4x cleaning the sandpaper using a brush. The pretty rubbish quality shoes started being too small a diameter, but after sanding became ok.

The drum was skimmed after the new sprocket welded 2000miles ago, so should be round.



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