BSA C10 C11 C12

BSA C10 C11 C12 Forum => Technical Section => Topic started by: steve70 on September 26, 2020, 02:49:15 am

Title: c10 front brakes
Post by: steve70 on September 26, 2020, 02:49:15 am
probably an old topic, front brakes on bike have always been bad, new linings, took them off, look glazed, took all high spots off the put whole unit in and kept turning and sanding till both shoes were touching evenly , still the same not good, rear brakes do the work, oddly if the bike is pulled backwards they lock up as should, is there something simple im missing, C11 works fine and they are identical
Title: Re: c10 front brakes
Post by: steve70 on September 26, 2020, 06:42:31 am
 after posting had another look, found a brake arm off a A7 dropped it down to keep pull almost straight, big difference , leverage  . the A7 arm was an inch longer , the brakes now are good, and easier on the wrist,
Title: Re: c10 front brakes
Post by: Owen on September 26, 2020, 06:57:39 am
Many moons ago when my C10 needed a MOT. I watched as the tester did the brake test and snapped my front brake cable trying to lock the front wheel. Lucky I had a replacement to hand.  He got the front to 75 NM but not locking up and back to 105 NM which would lock up quite easily with modern linings. Therefore I ride accordingly.
Title: Re: c10 front brakes
Post by: timsdad on September 26, 2020, 07:40:49 am
It's how they were designed to be but, as road surfaces improved, the brake design stayed much the same for several years.

BSA brakes will work quite well once they're bedded in properly. This can  take a few hundred miles of proper use but, if the bike is stood up for a period, the bedded-in linings glaze up again and you have to start all over again.


Ray
Title: Re: c10 front brakes
Post by: BSAc11g on September 26, 2020, 10:17:21 am
The biggest problem with C series brakes is the linings they were designed to se are no longer made
The nest problem is most drums are way past the wear limit so the contact angles are wrong
The nest problem is no one actually understands self -servo mechanical brakes any more  and the web is full of fixes that are only applicable to power assisted brakes.

To work properly the shoe has to be machines to a slightly bigger radius that the drum
So when the leading edge of the shoe hits the drum, the rotating force of the drum is transferred to the shoe pushing it hard against the rear pivot and then causing it to flex into full contact with the drum .
For this to happen the rear of the shoe has to be very close to the drum.
This is the theory behind fully floating brake shoes .
So start with the pivot.
Most have some sort of adjustment so the shoe can be brought closer to the drum .
If not then the shoe itself usually has a slipper that can be removed & packed out to bring the shoe closer to the drum .
make sure that the operating lever on the backing plat can not get to 90 Deg to the cable
Again most BSA levers have a double square so you can move the lever with respect to the brake cam .

Have close look at the cam and the wear face of the shoe.
Both will probably be worn with a groove so the brake makes contact with the drum, the the pressure is relieved as the cam hit the wear hole .
 You want the leading shoe to travel faster so the cam should be set up so the leading shoe is activated by the outer edge of the cam & the trailing shoe the inner .
Lots of clowns who do not understand the principles tell you to do it the other wah, which is correct for power assisted hydraulic brakes, hot hand powered motorcycle brakes.
Mind you a lot of riders in the day had no idea either judging from all of the "readers tips" I see in period publications.

Then we come to the levers , cables & perches .
Almost every BSA I inspect for road worthyness has the pivot hole in both the lever & the perch worn quite oval , drastically reducing the leverage.
If yours are not round & close fitting, replace them or bush them.
And finally there are a myriad of different lengths of levers from the pivot hole to the lever ( forgot it's actual name ) .
If they are not matched you loose leverage
After that there s the cable itself and in particular the outer.
A lot of cheap ones have a open spiral wound outer which becomes a great big spring when you pull the brake lever so get good quality ones.
The most expensive brake cable is a lot cheaper than taxi fare too & from the casualty department , let alone physiotherapy every day.

The we come to proper lubrication.

Plain bowden cable should be lubricated with a dry teflon solution.
I use Tri-Lube, it comes from push bike shops & is used to lube gear change cables .
It is not cheap but a 4oz bottle will last for a decade or more.
Nylon lined cables can be lubed with the same goop or kerrosene
WD 40 must never ever get anywhere near a nylon cable and in fact has no place on a C series apart from the points.

Now to get into the esoteric stuff.
A wound cable unwinds when you stretch it .
so it must be able to rotate when pulled.
In most cases this is supposed to be done by the brake end which has a ball or pear type fitting on it ( clutch is the same )
In order to rotate the cable end and the socket it fits into must be smooth & lightly lubed .

In practice this never happens & the ball ends get mutilated causing a lot of that effort you are applying going into unwinding the inner cable.
The solution to this is to fit a floating drum to the handle bar end .

Even better if you do this the cable will last forever
Title: Re: c10 front brakes
Post by: steve70 on September 26, 2020, 10:23:59 pm
Trevor
ive got quite a bit out of this, some  wear issues I have addressed,  and some not, when the bike was in pieces, I put new spokes in and skimmed the drum back to round then, it wasn that bad , the fitting arm to square is tight   the  angle with cable looks as it should,  I hadnt even given the cable a thought, it is new. nor wear on the shoes and cam. I have another bike unnamed with a similar sized front drum that locks up with little pressure , so a relook today, the longer arm made a substantial difference.
Title: Re: c10 front brakes
Post by: BSAc11g on September 28, 2020, 05:47:33 am
The only BSA I have ever owned that the front could not be locked up are the girder framed ones.
I could have made them work that good as well but you really don't want a strong front brake with BSA girders.
Well perhaps a C 10 as it has very limited engine breaking capacity .
Title: Re: c10 front brakes
Post by: timsdad on September 28, 2020, 07:25:42 am
Yes, a C10 has very limited engine breaking capacity - and not much engine braking either!


Ray
Title: Re: c10 front brakes
Post by: ThomasC11 on September 28, 2020, 08:43:57 am
Hi Trevor, this is the first well justified description about this topic I have ever seen. However, I have problems to understand some details. Could you manage to make a text with some explaining pictures for our technical tips?
Cheers, Thomas
Title: Re: c10 front brakes
Post by: BSAc11g on September 29, 2020, 08:30:27 am
Anything that is unclear, please ask .
The current running bikes are all girders so no photos of C series brakes to upload.
Search Self energising or self servo mechanical drum brakes should bring up  lots of information with better diagrams than I could ever do .
The important thing is the speed of application rather than the force of application
Si the leading shoe should normally be activated by the outer edge of the cam on a single leading shoe brake because it moves further and there fore faster then the lower edge.

Most riders who come in with rubbish brakes have a gap between the shoe & drum you can measure in fractions of an inch
To work that gap  should be .050" tops .

Your hand can only apply a few kg of force onto the brake lever , unless you arm wrestle with Big Arnie & beat him.
Allowing a 100:1 leverage your puny wrists are not going to stop 100 Kg of motorcycle at 60 mph unless you can use the momentum to assist you.
So all you need to do is poke the leading shoe into the drum and hold it there tight enough for the drum to force the shoe to flex into the drum
Think about grinding on a bench grinder and all those times you go the angle wrong & stalled the wheel, generally taking a good size lump out of the abrasive .
The trailing shoe is only there  for stability and is not supposed to do much in the way of braking because the drum effectivly pushes the shoe away.
The only time it is doing much in the way of work is when you are on a hill pulling the brake to stop yourself rolling backwards.
I gave up writing to editors of magazines correcting rubbish they they have printed decades ago and sine the web has fired up the power of the masses means what I know to be correct is wrong , along the lines of eat schit because 200,000,000,000,000,000,000,000,000 flies can't all be wrong.
Very easy to pinch some ones pretty diagrams the do a cut & paste to make your self appear to be intelligent.
There would be almost no one alive who drove cars in the mechanical brake only days and everything published since is all based on hydraulic power assisted brakes where the pressure applied on the the shoes IS high enough to provide effective braking  force .
Title: Re: c10 front brakes
Post by: ThomasC11 on September 29, 2020, 09:58:16 am
OK!

Quote
So the leading shoe should normally be activated by the outer edge of the cam on a single leading shoe brake because it moves further and there fore faster then the lower edge.

What is a "leading shoe"? What is the "outer (and lower) edge of the cam?

Quote
So all you need to do is poke the leading shoe into the drum and hold it there tight enough for the drum to force the shoe to flex into the drum

I don't get it.
Title: Re: c10 front brakes
Post by: c11jim on September 29, 2020, 12:58:34 pm
Hi Thomas,
In the diagram below, if the wheel is rotating in the direction of the arrow the leading shoe is the one on the left. As the drum rotates against it the friction between the drum and the shoe pulls the shoe out harder against the drum. This is called the self servo effect of the leading shoe. When Trevor refers to the outer edge of the cam I assume he means the lower edge in this diagram (that is, the edge closest to the outside of the drum).

Hi Trevor,
I think you've got the effect of the cam the wrong way around. When the brake is applied both edges of the cam move the same distance and at the same speed, but they effect each shoe differently because the outer cam edge is further from the pivot point of the shoes than the inner edge. The cam is like a small gear wheel acting on two larger gears (the shoes) with the centre of the large gear wheels being the pivot point of the shoes. The shoe being pushed by the outer edge of the cam is effectively a larger gear than the other shoe because the contact point is further from the centre. As larger gears rotate slower than smaller ones, the shoe being pushed by the outer edge of the cam will move slower than the other one. Also, as a larger gear has more torque applied to it the shoe pushed by the outer edge of the cam will have more force applied to it even though it is moving slower. So the question is, what's more important, the force applied to the shoe or how fast it's pushed out?
Jim
Title: Re: c10 front brakes
Post by: ThomasC11 on September 29, 2020, 01:38:03 pm
Great, Jim, that helps a lot.

A picture is worth a thousand words, indeed. That is why I try to write comprehensive explaining texts for the Technical Tips section so that this information isn't lost after a while. Especially for such tricky situations like this. and especially for non-anglophones...  ;D

As far as I now understand, this is the same effect as for modern disk brakes at front wheels which get more pressure on it. The front wheel in contact to the road is then the equivalent of the leading shoe in the drum.
 
Best, Thomas
Title: Re: c10 front brakes
Post by: steve70 on September 29, 2020, 08:18:01 pm
As far as I can see the only adjustment on C front brake is the cable, after reading first post, checked shoes and linings probably werent thick enough, and probably making the matter worse by mating linings to drum, had another set with a thicker lining,  which cut the gap down and improved braking,also using the correct lever, so speed is a big factor, still room to improve tho. They must have been able to lock up when new, but having such a small contact area as soon as wear takes place they become a lot less effective and the rider just gets used to it. I saw that diagram posted Jim, it makes the topic easier.
The one thing that interests me is how easy and with little  effort it is to lock the front brake up pulling the bike backwards
Title: Re: c10 front brakes
Post by: ThomasC11 on September 29, 2020, 08:49:46 pm
You can adjust it also with the drum lever position by turning it by one position on the square cam, Steve.
Title: Re: c10 front brakes
Post by: camman3 on September 29, 2020, 08:55:25 pm
As far as I can see, nobody has mentioned the importance of centralising the fulcrum pivot point, by slackening lock nut, applying brake and re tightening nut :-\
https://bsac10c11c12.co.uk/smf/brakes-wheels-service-sheets/front-hub-brake-(7-inch)/
Graham
Title: Re: c10 front brakes
Post by: ThomasC11 on September 29, 2020, 09:05:09 pm
Puuh, maybe I am the only one who is not too happy with the old BSA workshop manuals but at least I do not understand what the fulcrum pivot point is nor do I see a lock nut in the drawing. Dementia or bad description...  :-[
Title: Re: c10 front brakes
Post by: camman3 on September 29, 2020, 09:25:56 pm
Third paragraph on first service sheet in that link, states the importance when fitting new linings
The section of the nut can be seen in drawing on same sheet.
Title: Re: c10 front brakes
Post by: steve70 on September 29, 2020, 11:39:54 pm
Ive seen and done that
Title: Re: c10 front brakes
Post by: Ginge on September 30, 2020, 02:35:02 am
You’ll be right Steve. Wellington doesn’t have hills does it?

My pivot points were wrapped in brass shim stock by the previous owner to take up wear.  I removed them and ended up with worse brakes.  That “grab,catch and flex” self servo effect is the answer. You just need to gauge the pivots out. 

Shim stock probably isn’t the best answer though.  Oversize linings from a brake specialist might be.

Cables do make a difference. Cheap pattern cables are not worth the effort.
Title: Re: c10 front brakes
Post by: steve70 on September 30, 2020, 06:48:02 am
Ginge
Im in the Wairarapa, but my drive is 100 metres all down hill, so its a good test , Ive got another set of linings on some shoes, not sure what model, but they are steel  amongst a whole lot of parts I bought some time ago, the grip is by hand a lot better than what I have by miles, I cant get that softer lining  material here,and there is only one place that does it and hes almost olde rthan the bike so im going to bond these onto existing shoes, probably have asbestos in them, but so have my lungs:)   
Title: Re: c10 front brakes
Post by: ThomasC11 on September 30, 2020, 09:04:23 pm
Quote
Most riders who come in with rubbish brakes have a gap between the shoe & drum you can measure in fractions of an inch
To work that gap  should be .050" tops .
Today I opened the front brake and checked the clearance. It's about four times this value. However, there is no possibility to adjust it...
Title: Re: c10 front brakes
Post by: Owen on September 30, 2020, 09:57:51 pm
You could always adjust the cable/rod to take up the slack?
Title: Re: c10 front brakes
Post by: chaterlea25 on October 01, 2020, 12:24:28 am
Hi All,
Thomas the 050. measurement is inch measurement  =1.25mm
4 times that = 5mm    :o
What thickness are the linings on the shoes?  memory tells me new linings are about 4mm on the 5.5inch brake
and about 5mm on the 7inch front shoes

John
Title: Re: c10 front brakes
Post by: ThomasC11 on October 01, 2020, 08:54:51 am
Yes, about 5mm. I have not measured the thickness now. But they are relatively new. In my opinion gap and thickness are primarily not important because you adjust the cable/rod anyway. Of course I do that. But at some point the shoes start to scratch and you have to adjust them accordingly.

I'm wondering if Trevor's hint (.050" tops) is realistically applicable here and if you just have to pay attention to the right angle between rod and cable (after adjustment, of course).
Title: Re: c10 front brakes
Post by: chaterlea25 on October 01, 2020, 08:38:25 pm
Hi Thomas,
I went and measured up a 5 1/2in. brake and brake drum today
The old linings are worn to approx 0.1in (2.5mm) new ones measure 0.155in (just less than 4mm)
The difference between the shoes and drum is approx 0.070in. (1,75mm)
It looks like if I fit the new linings I will have to turn them down to fir the drum?
( I did not have the springs fitted or parts cleaned which might make a difference?)

Also I noticed that the 5 1/2in brake does not have a movable shoe pivot as used on the 7 and 8in. brakes

If your brake shoes / drum have almost 5mm difference you have a problem ???
Are the steel pads fitted to the cam ends of the shoes ? this might account for some of the difference you measured

As an aside has anyone experimented with modifying to floating shoes with asymmetric linings as used on later BSA models ? (pic below)

John

Title: Re: c10 front brakes
Post by: ianinglis on October 02, 2020, 06:02:07 am
looking at that diagram you could flip the shoes over and fit them incorrectly or am i missing something???




ian
Title: Re: c10 front brakes
Post by: timsdad on October 02, 2020, 07:22:39 am
Shoes can often be fitted wrong by swapping then over but a lot of braking efficiency is lost if the leading edge is trailing instead of biting first.


My old bikes have usually been quite worn up when I've bought them so, if the brakes are not fit for purpose, I can get them working well enough by just replacement or repair of worn parts, proper assembly and bedding them in well. I use my old bikes because I love them for their faults and foibles and to transport me back to my younger days as well as my destination.

I have newer bikes equipped with Brembo, Tokiko and Nissin discs to stop me on a sixpence so my BSAs just need a bit more forward planning and a much harder squeeze. If you want really good brakes, just get yourself a Hinckley Triumph for everyday use. You'll never get a puny tin drum to do a stoppy.


Ray
Title: Re: c10 front brakes
Post by: Tman on October 02, 2020, 08:31:23 am
looking at that diagram you could flip the shoes over and fit them incorrectly or am i missing something???
ian

People always could, did and probably still do, then they promptly go on Net forums and complain about how they couldn't get their awful brakes to work on their old "Brit" etc etc.
Much-maligned, just like that other butt of the ignorant, Joe Lucas. ;)
Title: Re: c10 front brakes
Post by: ThomasC11 on October 02, 2020, 05:14:38 pm
Thank you, John!

Quote
If your brake shoes / drum have almost 5mm difference you have a problem

Hm! My outer brake shoe diameter is 136.8mm whereas the inner drum has 139.7. So about 3mm difference. There is a slight burr on the drum edge. The linings have about 3mm thickness. What now?  :-\

Cheers, Thomas
Title: Re: c10 front brakes
Post by: chaterlea25 on October 02, 2020, 06:25:41 pm
Hi Thomas,
Did you check the cam end of the shoes for the steel pads?
these are folded around the ends of the alloy shoe, and are approx 1.5mm thick
the 2 of these will make up your missing 3mm

John
Title: Re: c10 front brakes
Post by: Owen on October 02, 2020, 06:34:48 pm
Those shoes don't look right to me. They are different to the normal 29-5850 5 1/2" ones.  Look at John's first picture.
Title: Re: c10 front brakes
Post by: ThomasC11 on October 02, 2020, 07:50:18 pm
Hm, there are no steel pads...  ??? Interesting! I didn't know that they should be there (can't see them in the Draganfly shop) and I have no idea if the shoes are right. I see that Draganfly sell new shoes only in exchange with the old ones. But will they accept if the shoes are wrong...?
Title: Re: c10 front brakes
Post by: steve70 on October 02, 2020, 08:48:40 pm
just in process of fitting 4mm linings now, material is far superior and more grip than what was on there,in my case the material was wrong and badly applied and to thin,  the shoes I have look the same as Johns photo but I wasnt aware of steel caps either, there are none on either of the two Cs I have, they would be easy to make if they should be there, what thickness are we looking at, having them there could make things a bit tight
Title: Re: c10 front brakes
Post by: Owen on October 02, 2020, 09:51:56 pm
Look at this pair of shoes https://bsac10c11c12.co.uk/smf/gallery/?sa=view;id=2702 they are the correct ones.
Title: Re: c10 front brakes
Post by: chaterlea25 on October 02, 2020, 10:08:20 pm
Hi All,
Yes it looks like Thomas's brake shoes are different ??
The linked to shoes have the steel pads (look carefully)
If I think of it I will take a photo of the shoe ends tomorrow where the steel pads are clearly seen

John
Title: Re: c10 front brakes
Post by: ThomasC11 on October 03, 2020, 07:03:06 am
Difficult to see, indeed... Anyway, thank you fellows. It really seems that I have the wrong shoes (looks like Bantam). I learn this after already 8 years in my hands... so, better not stopping discussing here.  :D Draganfly offers shoes out of steel (29-5850FA) and alloy (29-5850FB). The price is almost the same. Any idea why this difference and what is better?
Title: Re: c10 front brakes
Post by: steve70 on October 03, 2020, 07:07:50 am
Trevor thanks for that earlier post, have fitted linings from an old set of shoes I bought with a lot of other c parts sometime ago, the shoes were steel probably from an earlier model, the linings gave the appearance of little use, your comment about the brakes being better earlier I think would be because of the asbestos content, im sure the ones ive used are, so its masks etc, glued and riveted they fitted perfectly  which with a little sanding , 4mm thick which seem the right thickness. The result is a front brake that locks whithout to much wrist pressure and combined with back brake makes a very safe bike.
The front brake actually improves the faster the speed relative, ive gone back to the short arm so angle is a little under 90 degrees, there is obviously softer lining material out there but what was put on mine was to hard and no grip , the gap between linings and drum is as close as I can get it without interference.   
Title: Re: c10 front brakes
Post by: steve70 on October 03, 2020, 07:11:36 am
If steel caps were a standard fitting on the cam end  there is no way a 4mm lining would fit
Title: Re: c10 front brakes
Post by: Owen on October 03, 2020, 07:47:14 am
The steel shoes are the earlier offset (handed)  shoes for pre 49 models part No. 24-7767 &24-7768. They only fit the earlier brake plates and tend to twist   inwards when applied. 49 onwards the went to the centrally alloy shoes which did not suffer from the twisting.
Title: Re: c10 front brakes
Post by: steve70 on October 03, 2020, 08:26:49 am
that is the shoes I got the linings off
Title: Re: c10 front brakes
Post by: BSAc11g on October 03, 2020, 10:30:40 am
Trevor thanks for that earlier post, have fitted linings from an old set of shoes I bought with a lot of other c parts sometime ago, the shoes were steel probably from an earlier model, the linings gave the appearance of little use, your comment about the brakes being better earlier I think would be because of the asbestos content, im sure the ones ive used are, so its masks etc, glued and riveted they fitted perfectly  which with a little sanding , 4mm thick which seem the right thickness. The result is a front brake that locks whithout to much wrist pressure and combined with back brake makes a very safe bike.
The front brake actually improves the faster the speed relative, ive gone back to the short arm so angle is a little under 90 degrees, there is obviously softer lining material out there but what was put on mine was to hard and no grip , the gap between linings and drum is as close as I can get it without interference.

That is the self energizing coming into effect.
The brake should also be stronger if you jab on and more gradual if you pull on slowly.
The important thing is you can now stop.
Title: Re: c10 front brakes
Post by: chaterlea25 on October 03, 2020, 09:37:01 pm
Hi All,

Quote
If steel caps were a standard fitting on the cam end  there is no way a 4mm lining would fit

Steve, the shoes with steel pads have and had 4mm linings,
The photos I posted earlier show this, it will fill the brake drum nicely when the new linings are fitted
The steel pads are crimped in place and not very noticeable on the picture of the new shoes Owen linked to

Thomas's brake shoes had a large gap between the shoes and drum, leading me to ask if the steel pads were missing
The can become detached for various reasons, These ones look almost cast in place?

John
Title: Re: c10 front brakes
Post by: Owen on October 03, 2020, 10:28:53 pm
Googling the 1075 on thomases shoes as BSA 1075 comes up as tiger cub / bantam shoes GF 1075. so that suggests you have the wrong shoes?
Title: Re: c10 front brakes
Post by: steve70 on October 04, 2020, 02:32:45 am
Thanks John, obviously they are suppose to be there, they werent on mine, brakes are back in now, it was a tight fit and had to sand the high spots off to get them in with them on I dont think they would have gone in if they were there. Two other spare sets dont have them either , I suppose it comes down to what size linings BSA used with the aluminium shoe
Title: Re: c10 front brakes
Post by: steve70 on October 04, 2020, 03:02:38 am
I will have to retract that, looking again at the spare ones they do have steel caps, I know the set on the bike didnt
Title: Re: c10 front brakes
Post by: ThomasC11 on October 04, 2020, 06:52:17 am
Great information from you all! That confirms I have Bantam shoes. Yesterday I've sent a message to Draganfly asking if they deliver new shoes even if I can offer only those from a Bantam (they only deliver in exchange). 

Cheers, Thomas
Title: Re: c10 front brakes
Post by: Owen on October 04, 2020, 06:59:23 am
So do we have anyone with a C and a bantam that can compare the two to see the difference e.g. height, width,  linings etc.?
Title: Re: c10 front brakes
Post by: steve70 on October 04, 2020, 08:37:06 am
My stuff up,  took wheel off again today and there are steel caps just didnt see them, obvious that aluminium wouldnt last long against a steel cam, plus side is wear is dead even over both linings, apologies John, you pointed out , took time post photos, just rushing and not looking.
Title: Re: c10 front brakes
Post by: chaterlea25 on October 04, 2020, 03:45:56 pm
Hi Steve
No worries,
Live and learn  ;D  or something like that

Just happy to be able to help sometimes

John
Title: Re: c10 front brakes
Post by: ThomasC11 on October 05, 2020, 02:41:15 pm
I just got message from Draganfly. They don't sell brake shoes in exchange if I send them Bantam shoes. Hm, I now need other sources for C11 front shoes. Any help is welcome.

Cheers, Thomas
Title: Re: c10 front brakes
Post by: chaterlea25 on October 05, 2020, 09:30:12 pm
Hi Thomas,
It might be worth asking "GP Motos Anciennes" on ebay,  They have a lot of NOS brake parts
I am pretty sure I do not have any spare. The wheel I took the photos of was an ebay purchase

John
Title: Re: c10 front brakes
Post by: ThomasC11 on October 06, 2020, 07:20:24 am
Hi John,

I already called GP Motos. C11 shoes are out of stock but he wants to check again and will send an email. The same for British Only Austria. And no stock at Classic Motorcycle Spares. It seems as original shoes are not available anymore...  :-\

Anyway, thank you for your kind remark and cheers, Thomas
Title: Re: c10 front brakes
Post by: ThomasC11 on October 06, 2020, 04:23:04 pm
I got a message from Gary Parkin of GP Motos. He has found brake shoes which can make a pair. They are correct in the dimensions for the hub. The only problem is one is made from aluminum the other is zinc. He says that this will not affect any performance (zinc weights factor 2.6 of aluminum). He can reline these for €45 plus postage. I am not sure about the weight difference. Does somnebody have any experience with that?
Title: Re: c10 front brakes
Post by: camman3 on October 06, 2020, 04:32:34 pm
Theoretically I cant see any reason why the weight of the shoe will make any difference, as it will not effect the force applied, contact area, or friction of linings.
May have slightly different heat dissipation values.....but hardly an issue on a C  :)
Graham
Title: Re: c10 front brakes
Post by: ThomasC11 on October 06, 2020, 05:25:12 pm
Hi Graham!
Quote
May have slightly different heat dissipation values.....but hardly an issue on a C
Heat dissipation for aluminum is twice as high as for zinc. But I agree, that shouldn't be a problem for a 'C'. The weight diffence might introduce a "hidden" problem but I too don't see it.
Thomas
Title: Re: c10 front brakes
Post by: Owen on October 06, 2020, 05:41:40 pm
Have you tried martyn Bratby, he might sell some to you?
Title: Re: c10 front brakes
Post by: ThomasC11 on October 06, 2020, 06:12:25 pm
No, unfortunately I neither have any contact data nor do I find them in the net.  :(
Title: Re: c10 front brakes
Post by: Owen on October 06, 2020, 06:49:26 pm
I have sent you his contact details by PM.
Title: Re: c10 front brakes
Post by: ThomasC11 on October 16, 2020, 01:21:57 pm
After looking around I decided to take the brake shoes from GP Motos Anciennes in France. They arrived yesterday and fit perfectly well. Today I took a test ride (no wet sumping after some weeks!). The front brake is now sufficient for a regular stop and for emergency both breaks do a great job considering the machine age. Thanks to all for their advice and help.

Cheers, Thomas
Title: Re: c10 front brakes
Post by: Owen on October 16, 2020, 05:57:56 pm
Glad you got it sorted.
Title: Re: c10 front brakes
Post by: isleofmanpaul on October 16, 2020, 07:53:47 pm
Hi, got the shoes on my Comet front brake relined, used "Friction Services (Bristol) Ltd . Got them back in just under a week , 4 shoes , paid £46.74 incl VAT ,well pleased .
 It's nice to be able to recommend someone , just saying . :)
Title: Re: c10 front brakes
Post by: Owen on October 16, 2020, 08:11:39 pm
I've got mine from  Martyn Bratbury and had no problems.
Title: Re: c10 front brakes
Post by: ThomasC11 on October 22, 2020, 12:30:30 pm
Now that I have got the right brake shoes for my C11, I can give away the pair I have installed so far. Probably they are shoes of a Bantam. But I am not sure.

Also I can give away a speedometer cable. It is new and 125cm long.

Everything is free of charge and I also pay the shipping costs because I always get great help here. So if you can use it, please send me a PM.

Cheers, Thomas
Title: Re: c10 front brakes
Post by: BSAc11g on October 26, 2020, 12:41:36 pm
Hi Thomas,
In the diagram below, if the wheel is rotating in the direction of the arrow the leading shoe is the one on the left. As the drum rotates against it the friction between the drum and the shoe pulls the shoe out harder against the drum. This is called the self servo effect of the leading shoe. When Trevor refers to the outer edge of the cam I assume he means the lower edge in this diagram (that is, the edge closest to the outside of the drum).

Hi Trevor,
I think you've got the effect of the cam the wrong way around. When the brake is applied both edges of the cam move the same distance and at the same speed, but they effect each shoe differently because the outer cam edge is further from the pivot point of the shoes than the inner edge. The cam is like a small gear wheel acting on two larger gears (the shoes) with the centre of the large gear wheels being the pivot point of the shoes. The shoe being pushed by the outer edge of the cam is effectively a larger gear than the other shoe because the contact point is further from the centre. As larger gears rotate slower than smaller ones, the shoe being pushed by the outer edge of the cam will move slower than the other one. Also, as a larger gear has more torque applied to it the shoe pushed by the outer edge of the cam will have more force applied to it even though it is moving slower. So the question is, what's more important, the force applied to the shoe or how fast it's pushed out?
Jim

Jim,
In your diagram the cam should rotate in a clockwise direction so the leading shoe makes a rapid contact with the drum & the trailing shoe which has no self servo effect gets the greater force applied to it .
I hope that is what I wrote .
If you are utilizing the rotation of the drum then you don't need all that much force to be applied.
Just enough to prevent the shoe skipping off the drum.
Title: Re: c10 front brakes
Post by: ThomasC11 on October 26, 2020, 05:48:29 pm
The brake shoes are given.
Title: Re: c10 front brakes
Post by: c11jim on October 28, 2020, 09:50:17 am
Quote
Jim,
In your diagram the cam should rotate in a clockwise direction so the leading shoe makes a rapid contact with the drum & the trailing shoe which has no self servo effect gets the greater force applied to it .
I hope that is what I wrote .
If you are utilizing the rotation of the drum then you don't need all that much force to be applied.
Just enough to prevent the shoe skipping off the drum.

Trevor,
I accept that the leading shoe needs to move out as fast as possible and the trailing shoe with more force, but to achieve that the cam would have to turn anti clockwise as I explained in my earlier post.
Jim
Title: Re: c10 front brakes
Post by: Lilyloodles on October 28, 2020, 12:11:01 pm
I've got mine from  Martyn Bratbury and had no problems.
Owen

Sorry to say that the issue I had with my brake shoes recently being way to thick were from Mr Bratbury
tony