The BSA A7-A10 Forum

Technical => Frame => Topic started by: BSA500 on 23.09. 2015 20:04

Title: Snatching front brake(TLS)
Post by: BSA500 on 23.09. 2015 20:04
Hi as per title my 8 inch twin leading shoe front brake is a tad-well-bloody dangerous and snatchy. When cool and damp it grabs like king kong at the slightest whiff of front brake use. Which in traffic is not good. Of course when warmed up it tends to fade and not give much feedback. I know most of the remedies but now I am going to really attack it(esp seeing as she's off the road for a few days as the chain snapped today-it never rains eh) so please chime in with your suggestions etc.
I will strip it down check the links /rods,clean the drum deglaze shoes if needed,camfer the leading edges etc etc.
thanks in advance Andy
Title: Re: Snatching front brake(TLS)
Post by: morris on 23.09. 2015 21:13
What type of shoe lining are you using?
Title: Re: Snatching front brake(TLS)
Post by: duTch on 23.09. 2015 21:27

 Iwas going to suggest
Quote
,camfer the leading edges etc etc.
...but you got it covered *smile*
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 24.09. 2015 08:41
Shoe lining is whatever the suppliers bond to the shoes,light brown if that helps *smile*. I will strip them and post pics. I noticed they should,according the the exploded images,have abutment pads but I don't think mine do. Again the strip and pics will help with that.
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 25.09. 2015 09:07
I think the pads in the pic (number 12 and 32  ) are missing,but I won't know until I pull the brake out. Link to pic below. That is the brake I have the 1968 tls

https://www.draganfly.co.uk/images/shop/a65/68/18.jpg
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 25.09. 2015 21:03
Well removed the brake shoes etc and no abutment plates so the shoes were not correctly positioned on the plate ever since I installed it(20+ years  *eek*). Here are some pics

(http://i11.photobucket.com/albums/a170/bsa500/DSC04653_zpsfxe1j9qp.jpg) (http://s11.photobucket.com/user/bsa500/media/DSC04653_zpsfxe1j9qp.jpg.html)


(http://i11.photobucket.com/albums/a170/bsa500/DSC04655_zps1jbcqjyn.jpg) (http://s11.photobucket.com/user/bsa500/media/DSC04655_zps1jbcqjyn.jpg.html)

(http://i11.photobucket.com/albums/a170/bsa500/DSC04656_zpsdadqqbe5.jpg) (http://s11.photobucket.com/user/bsa500/media/DSC04656_zpsdadqqbe5.jpg.html)

(http://i11.photobucket.com/albums/a170/bsa500/DSC04657_zpsayemduqc.jpg) (http://s11.photobucket.com/user/bsa500/media/DSC04657_zpsayemduqc.jpg.html)
Title: Re: Snatching front brake(TLS)
Post by: kiwipom on 26.09. 2015 02:12
hi guys, BSA 500, yes this is my one you can see the bits that you need,cheers
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 26.09. 2015 09:34
Bloody surprised that  it worked at all. Found when I took it apart the connecting rod for the levers was a little bent. This is not the first time either so that is prob to do with the unequal braking forces ?
Title: Re: Snatching front brake(TLS)
Post by: morris on 26.09. 2015 23:10
Shoe lining is whatever the suppliers bond to the shoes,light brown if that helps *smile*

The reason I was asking is because I recently replaced the aftermarket bonded shoes on the SA (full width hub) by the original shoes I still had lying around and which I relined with a set of nos Ferodo linings. It immensely improved the brake's performance in smoothness and stopping power.
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 27.09. 2015 11:25
Shoe lining is whatever the suppliers bond to the shoes,light brown if that helps *smile*

The reason I was asking is because I recently replaced the aftermarket bonded shoes on the SA (full width hub) by the original shoes I still had lying around and which I relined with a set of nos Ferodo linings. It immensely improved the brake's performance in smoothness and stopping power.

I shall sort out the plates etc and see how improved the stopping is. I have some spare shoes so if I need to I can have those relined  *smile*
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 28.09. 2015 11:56
Right as per usual the parts I need (37-2026 brake abutment pads) are not available-I have them on back order but its going to be at least 2 weeks if not more. Anyone know of a supplier who has these ???
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 03.10. 2015 20:21
I have had to order these from the USA so will update when fitted
Title: Re: Snatching front brake(TLS)
Post by: duTch on 04.10. 2015 00:02

 Took some detail the other day but work interfered with things, but if you need to make some, they're fairly simple
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 04.10. 2015 12:46
Thanks Dutch. I think that is something you can post as a sticky on the forum for all to see in case they run into the same issues. *smile*
Title: Re: Snatching front brake(TLS)
Post by: duTch on 05.10. 2015 00:42


 I thought I added this yesterday, so will anyway- and on the other page.

 I used the piece of paper and folded it around to;-
....show how a flat piece of 1/16" (1.6mm) sheet would look before folding, but if I had to make them, I'd use a bit of 1" SS RHS and fettle/'humour'  the folds *smile*

 I'll post in in your other thread too...when I find it
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 12.10. 2015 12:59
We now have a non snatching front brake(although a damp day will be the complete test of it). I had to shorten the outer sheath of the brake cable so it would reach???.
Title: Re: Snatching front brake(TLS)
Post by: duTch on 12.10. 2015 20:26

    *eek*
 
Quote
(although a damp day will be the complete test of it).
...I bet you're not really hoping for it...

 Good to hear you've had a win...  And a bonus extra life for the cable !           *smile*


 
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 13.10. 2015 12:58
Yep a win but it still has a judder under braking. Not many places round here that can check and true up a drum *sad2*
Title: Re: Snatching front brake(TLS)
Post by: Angus on 13.10. 2015 13:45
The A7 1961 just got MOT advisories on the braking effort fluctuating both front and back. I am told it is the drums out of true. Never had it before and have no idea of the cause.
Title: Re: Snatching front brake(TLS)
Post by: cyclobutch on 13.10. 2015 16:33
I’ve got a couple of bikes where some years I get MOT advisories for fluctuating brakes and the next year I don’t. None of them are what I would consider to be dangerous in operation, though on my Guzzi V50 (just passed this very weekend with no advisory) it is bad enough that if I ride long enough before applying the brakes (foot – linked brake) I get a lot of excess travel first off due to pad knock off.

I guess that if it bugs you enough then it’s supposedly best to have the drums skimmed when the wheel is all built up anyway.
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 15.11. 2016 20:22
Well now the weather is chilly the brake has gone back to grabbing like a ba****d again. *sad2*
Title: Re: Snatching front brake(TLS)
Post by: DuncanF on 18.11. 2016 20:36
Found it on a Triumph once. What was happening was that the TLS brake plate, was being used on a non-TLS hub. If you do that, the brake linings will overlap onto the section of the hub, where the spoke abutments are. This causes "sharp" edges to come into contact with the brake linings. If you look at the pics, the "sharp" edges I refer to, are the recesses where the ends of the spokes locate.

A proper TLS hub, has a flange, and the spoke recesses miss the brake lining material. One way round the problem, is to cut a small slice from the linings, so they miss the recesses. If the shoes aren't pulling exactly square  to the hub surface, it could make matters worse.

I'm not saying this is definitely the problem here, but it was one I found.
Title: Re: Snatching front brake(TLS)
Post by: Greybeard on 18.11. 2016 22:27
Without reading through the whole thread again: Has anyone suggested chamfering the leading edges of the shoes? I needed to do this to mine when they started grabbing.
Title: Re: Snatching front brake(TLS)
Post by: Rocket Racer on 22.11. 2016 22:26
Looking at the images, it appears you are running a late 60's wide shoe TLS on an early non flanged drum: so the brake shoes are trying to grip on a non brake area of the drum (where the spokes come in). The non flanged hubs are designed for narrow shoes.
Unless I'm missing something to run that brake plate you need to change the front hub.
Title: Re: Snatching front brake(TLS)
Post by: cyclobutch on 23.11. 2016 17:14
So the friction material on the shoes is wider than the drum brake area? Could/should/would you reduce the height of the friction material where it is currently contacting the non braking area of the hub ... or given that this is brakes we're talking of is that maybe a short cut to dusty death?
Title: Re: Snatching front brake(TLS)
Post by: Rocket Racer on 24.11. 2016 00:07
So the friction material on the shoes is wider than the drum brake area? Could/should/would you reduce the height of the friction material where it is currently contacting the non braking area of the hub ... or given that this is brakes we're talking of is that maybe a short cut to dusty death?

The original FWH iron SLS brakes with narrow shoes had a good reputation in period tests of the day, but were I understand prone to wearing out fairly quickly. So narrowing the shoes certainly an option.
Personally I would fit the later flanged hub designed for that brake plate. They are readily available 2nd hand.

The later TLS brake plate already loses any period authenticity, whereas the hub is quite subtle.
My SR has the later hub (note flange visible), with a modified SLS brake plate
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 09.12. 2016 20:35
I have been using this hub for over 20 years and its only been grabbing like a bitch the last couple. Only when its cold/damp. I have found a firm to skim the drums(judders) and a firm that can reline the shoes with a lining suitable for a brake lever and not hydraulic.
 I will see where that takes me first  *smile*
Title: Re: Snatching front brake(TLS)
Post by: metalflake11 on 09.12. 2016 21:21
I've experienced this three times over the years, twice on bikes, and once on a transit van. Just changing the shoes cured the problem straight off. I've got no idea why it happens, I only know the effect and the cure.
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 11.12. 2016 20:22
I've experienced this three times over the years, twice on bikes, and once on a transit van. Just changing the shoes cured the problem straight off. I've got no idea why it happens, I only know the effect and the cure.

I still have the original shoes the plate came with. First I will compare/measure against the current ones and then prob get that pair relined. They are the rivetted type against bonded currently on the bike. Be interesting to see if they are in any way different.
Title: Re: Snatching front brake(TLS)
Post by: Greybeard on 11.12. 2016 21:16
Grabbing could be down to the lining being loose on the shoes
Title: Re: Snatching front brake(TLS)
Post by: muskrat on 12.12. 2016 06:24
G'day BSA500. Modern bonding is as strong if not stronger than the old rivets. It also gives you more braking surface and can ware down further as there is no rivets. Snatching will occur if the shoes have worn to the point where the cam is almost at full lift and the drum isn't round any more through wear or over tightening the spokes.
Cheers
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 12.12. 2016 10:15
I am comparing the rivetted shoes against the bonded purely on dimensions etc. The old shoes were the originals when i bought this off the shelf about 20 years ago(£25 if I remember right *eek*). So they maybe a better option as they were made and fitted to the plate at the factory-I was told they were NOS. I am not saying the new type shoes are wrong, but they are being made 50 years later and I did get them off ebay with no obvious manufacturers markings. I don't remember the brake being horrible and snatchy when I first installed it, judder yes, evil snatching that scares the s**t out of me no  *eek*
Title: Re: Snatching front brake(TLS)
Post by: stu.andrews on 12.12. 2016 11:20
I have experienced the bonding of the linings to fail (on bonded linings of course!) due to rust on the shoes forcing the linings away. Riveted are better.
Title: Re: Snatching front brake(TLS)
Post by: cyclobutch on 12.12. 2016 14:58
I have experienced the bonding of the linings to fail (on bonded linings of course!) due to rust on the shoes forcing the linings away. Riveted are better.

And I've had that happen on Brembo brake pads.
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 30.12. 2016 20:07
I am in the process of getting the wheel ready for a drum skim. Checked the bearings a little notchy so have replaced them as the engineer said he sets the skim against the wheel bearings. While I was in the very cold shed I compared the original shoes against the aftermarket. The original shoe lining is 1/4 " ahead of the aftermarket shoe on the leading edge and the originals are a snugger fit into the brake plate. If that makes a difference we shall see  *smile*
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 21.02. 2017 14:04
I know takes me ages to sort things. Got the drum skimmed and he found it was 5 thou out of round good/bad??. Now to organise brake shoe reline.
Title: Re: Snatching front brake(TLS)
Post by: BrianS on 22.02. 2017 07:23
http://villiersservices.co.uk/index.php?main_page=product_info&cPath=66&products_id=146&zenid=gvafbdogt3k3a5t2t4dmo80te6 (http://villiersservices.co.uk/index.php?main_page=product_info&cPath=66&products_id=146&zenid=gvafbdogt3k3a5t2t4dmo80te6)
Title: Re: Snatching front brake(TLS)
Post by: muskrat on 22.02. 2017 08:15
G'day Brian.
Thanks for that link. Wish they were down here.
Years ago I took my shoes to a local brake & clutch place. The old (90+) fella there asked what I'd be using it for. I said racing. "This is what you need sonny." Real asbestos with copper wire wound through it!!! Yep  it worked but I held my breath when removing the wheels!!!
Cheers
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 22.02. 2017 10:10
I have a firm just up the road for me. EF Breen in Maidstone.
Title: Re: Snatching front brake(TLS)
Post by: Greybeard on 22.02. 2017 11:29
...Real asbestos with copper wire wound through it!!! Yep  it worked but I held my breath when removing the wheels!!!
Between 1968 and 1978 I was a motor mechanic. Back then brake dust was just blown out. Towards the end of my asbestos inhaling career I worked on a fleet of AEC artic tractor units. When you blow out the brake drums from those beasties the whole workshop is filled with a cloud of dust!  *doh*
Title: Re: Snatching front brake(TLS)
Post by: coater87 on 23.02. 2017 02:18
I know takes me ages to sort things. Got the drum skimmed and he found it was 5 thou out of round good/bad??. Now to organise brake shoe reline.

 I skimmed my own drums and the back was out 3 and the front was 7. So your right in the ball park if that makes you feel better. *smiley4*

 Of course I had to go out 8 on the back to clean out the rivet mark PO left there (which really isn't that bad of a mark, for a bike I don't think they did anything to maintain)

 Lee
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 23.02. 2017 13:37
Dropping the shoes off tomorrow and been quoted £8 per shoe  *smile*
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 06.03. 2017 11:21
Both shoes relined for £19. Did a quick trail fit and they now rub. I am hoping the lining is not too thick  :!. Any idea the standard thickness of the brakes shoes of the 1968 TLS brake?. I have to set it up properly hoping the rubbing goes away,I might fiddle around tonight.
Title: Re: Snatching front brake(TLS)
Post by: BSA500 on 07.03. 2017 11:45
I realised the shoes were rubbing because the shoes had gone 'over cam' as there was no cable holding them in the neutral position. Still bloody close to the drum now will only need a a small pull on the lever  *eek*
Title: Re: Snatching front brake(TLS)
Post by: JulianS on 07.03. 2017 13:52
The Ferodo catalogue gives the linings as 3/16 inch thick.
Title: Re: Snatching front brake(TLS)
Post by: muskrat on 07.03. 2017 19:05
G'day Julian  *welcome*.
Thanks for that info.

Now you can't just sneak in like that  *lol*.
Get over to  http://www.a7a10.net/forum/index.php?board=13.0  and tell us a bit about yourself and your interest in A7/10's.
Cheers