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Front brake SLS to TLS and Beyond

If I find my Norton-Imp under-braked, I was looking at a future option of a TLS conversion.

So I wondered if anyone has modified a Norton 8" SLS front brake to a TLS, I have looked at Owners modifications of BSA Gold Star units, Vincent brakes and perused the American Victory Library, which has efficiency tests of drum brakes, from alphabetically, Bridgestone to Yamaha. Even taking into account the Norton Commando drum brake, the 8" BSA/Triumph units of 1968-1970 and 1971-1973 come out on top as the better braked motorcycles, in fact pre-disc they out-brake all other British machines in production according to the data.

I didn't want to throw money @ a Commando unit as do not think it would look right, I was looking for a more period owner modified front brake with that amateur touch and bettered, signature of many units in the 60s, without throwing £1,000 at a Tickle unit!

According to the data a TLS unit, (bike moving forward,) can be up to 27% more efficient than a SLS, unit all things being equal.

Cheers

John H

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Well, having read the science of braking which is mind boggling and seems to be much more complicated, than trying to make your motorcycle go faster, i kind of like the challenge behind the concept of better brakes! It might be also, one small area in which I can be involved in a nice little mechanical development for which I do not have to sell the family silver!

I have even wondered whether the Post 1955 front brake plate, which fits like a Pressure cooker lid in the drum can be modified for the back brake, as it is stronger than the traditional flimsy rear drum backplate, but cannot try this as my build stuff is still 50 miles away at the moment!

Looking at prices my next project if any, will be AMC, BSA or Royal Enfield , specially with regards to costs! I always lusted after a Mark 2 Interceptor in my Bantam days!

Cheers

John H

Cheers

John H

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Front brake is 8" back brake 7" and the QD feature makes it very unlikely. I have seen a special cast back brake plate on a Commando that looked the business. A stiffening kit was on sale for the std rear brake.

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Why not go the whole hog and fit a car hydraulic tls backplate: something like a 8" Morris minor may be adaptable. You could then have all the fun of working out a suitable size master cylinder to use. It has been done before but I can't remember if I have seen it done on a Norton. The 1970s BSA/Triumph TLS brake is good I have one on a Golden Flash sidecar outfit which I fitted many years ago when they were still available new and quite cheap (c. £20!)

Rod

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Previously rod_thompson wrote:

Why not go the whole hog and fit a car hydraulic tls backplate: something like a 8" Morris minor may be adaptable. You could then have all the fun of working out a suitable size master cylinder to use. It has been done before but I can't remember if I have seen it done on a Norton. The 1970s BSA/Triumph TLS brake is good I have one on a Golden Flash sidecar outfit which I fitted many years ago when they were still available new and quite cheap (c. £20!)

Rod

There was a Norton outfit for sale somewhere on eBay a few months ago with all brakes converted to hydraulics using the Norton backplates, it really looked the business

Dick

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It is not clear from your post which hub and fork set-up you have. It does make a big difference.

There were a number of different front brakes fitted to Nortons, but you probably have an 8" 1957-on all-alloy hub. If so, the Commando and Tickle 2ls brakes should be an easy fit. The Triumph / BSA 2ls of 1968-70 is a much better item, and can be made to fit a Norton. The hardest part will be a torque pin to match the Norton slider.

The 8" half-iron, half-alloy hub fitted 1955-57 uses the same brake plate as the 8" iron half-width hub, functions just the same, and is heavier. That's the one on my bike... Not a desirable item.

It also makes a difference which fork you have. Up to 1960, the yokes were 7" centres, and 7 3/8" afterwards. That gives lots of extra room for bigger brakes (and tyres), but also compatibility issues. There are lots of detail differences in fork sliders, I think the lug on the right leg for the Manx brake plate disappeared from the roadster sliders in 1957

If you want to fit an alloy 7" brake plate to the rear of a Norton, the 1950-53 bikes got an alloy front brake plate. It is lots stiffer, but will give you lots of entertainment making it fit the rear. You may find it easier simply to buy a plate made for the job- I know Norvil offer one for early s/arm (with torque stay) and later s/arm (brake torque goes into the fork end lug).

Paul

Previously john_hall1 wrote:

If I find my Norton-Imp under-braked, I was looking at a future option of a TLS conversion.

So I wondered if anyone has modified a Norton 8" SLS front brake to a TLS, I have looked at Owners modifications of BSA Gold Star units, Vincent brakes and perused the American Victory Library, which has efficiency tests of drum brakes, from alphabetically, Bridgestone to Yamaha. Even taking into account the Norton Commando drum brake, the 8" BSA/Triumph units of 1968-1970 and 1971-1973 come out on top as the better braked motorcycles, in fact pre-disc they out-brake all other British machines in production according to the data.

I didn't want to throw money @ a Commando unit as do not think it would look right, I was looking for a more period owner modified front brake with that amateur touch and bettered, signature of many units in the 60s, without throwing £1,000 at a Tickle unit!

According to the data a TLS unit can be up to 27% more efficient than a SLS, unit all things being equal.

Cheers

John H

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Previously robert_tuck wrote:

Front brake is 8" back brake 7" and the QD feature makes it very unlikely. I have seen a special cast back brake plate on a Commando that looked the business. A stiffening kit was on sale for the std rear brake.

I thought there was a difference in size after I posted that idea, what a pity Norton didn't make them both 8"!

John H

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I have 2 sets of yokes 7" and Commando 7 3/8ths, and two sets of Sliders late 1940's, (1948) with mudguard mounting lugs lower down off, originally "Long" Road-holders

The front hub is the dual-metal type cast-iron and alloy pre-1955, same idea Veloce used on their machines. All the stuff came off old race bikes, as did both sets of sliders, (not broken by me I may add).

The pre 1955 dual metal hub units, despite their unsprung weight disadvantage/penalty are reputedly less likely to fade under duress and apparently at one time where sought after to convert for racing purposes!

My pre 1955 front brake plate which fits over the drum, had already been drilled with holes fore and aft and now Sports a home-made, moderately sized air-scoop with mesh over the front pepper-pot area, which were drilled in little small arcs! 14 holes of 2 sizes, small probably 9 x 1/8th and Large probably 5 x 1/4 inch and 5 x 1/4 rear, at the moment. It has marks on it that looks like someone attempted to Araldite an air scoop on it, by drilling little, blind holes in the plate!

The idea used to be to calculate roughly air flow through the front scoop minus mesh restriction and work out exit flow for best cooling effect! Theoretically air swirling round inside momentarily aids cooling, some manufactured units use cross-flow air also, with holes in both sides of the drum!

The whole idea as most would know, is to stop the brake drum expanding, leading to a increasing gap between the drum hub and the brake shoes and this the hub, pulling away from the shoe position leads to a reduced contact point to perhaps zero contact, AKA brake fade, the process being facilitated by excessive heat.

On Morgan cars they now supply specially deep-finned hubs and I believe Beart and others had deeply finned hubs on their Manx Nortons and G50's and 7R's. After-markets finned collars//"Muffs" are much less effective!

Somewhere I saw a picture of a 1950s/1960s Girling 3 shoe brake and the most amazing 3-shoe brake can be found on 1960s Alpha Romeo cars with lovely sculptured detailed deeply finned Alloy hubs with finned slots angled for cooling across the brake drums edge! See (Youtube). Of course on cars the mechanism is the reverse way round in fixed and rotating provision. Probably a 3 brake shoe unit would have been the next stage of development had discs not come along! 3 smaller shoes, fit a circular drum much better than 2 larger shoes!

But it would be down to manufacturing costs I presume. Hydraulic hybrid units are interesting and a Bendix conversion has been down on at least one BSA, I hate brake fluid though, thoroughly nasty stuff!

I will have a Front Brake plate off a BSA/Triumph 8" Conical hub unit soon, if not for this build it may come in for a Street scrambler project, I have an Atlas engine and a A65 Firebird Scrambler frame, though now I have found out a BSA pre-unit twin or Gold Star single have more room in them, duh!

I have a picture of a Norton Featherbed frame ISDT machine. apparently they worked quite well, when strengthened and braced appropriately! The ultimate street scrambler was the G50 engined CSR, I think they all went to the USA and when tested by Cycle in 1962, turned out 121 mph plus, now that really was a World beater, the last one I saw for sale was £18,000 and makes £15,000 Triton prices look a little silly by comparison!

Insomnia a bitch, not back off to bed, my Father suffered from it and now I question, just what we really inherit in our genes!

Cheers

John H

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Okay, I now have a Triumph/BSA 8 inch Front Conical brake plate to play with, trouble is the air scoop intake has a piece missing, smashed out!

Ddoes anyone know what they are made of and if they can be repaired?

Looks like the front wheel spindle on the BSA/Triumph may have been larger, unless it had a thicker bush and I think there was slight clearance for a self centring effect for floating type brake shoes!

This TLS 1971-1973 and the previous 1968-1970 BSA/triumph unit in tests of standard production units, come out as the best performers and are evidently significantly better than the Commando unit even with stiffening upgrade plate, although when they have them in, RGM have a brake plate unit, in which the brake plate has been recast with stiffening webs in the moulding!

Can't speak for John Tickle stuff and I am not prepared to spend £1,000 plus to find out!

Here is a most useful site and probably the single most useful site I have found to do with modification and technical stuff..http://victorylibrary.com/brit/2LS-table.htm

Interestingly enough I was reminded in a publication about an effect on leverage and drum brakes and had experience the same effect, when I was a teenager I used to wheel my D10 Bantam backwards down a drive way with a steep slope, because it was fun to zoom up but the width didn't allow you to turn the bike round without a struggle! After reading an experience of someone else, he also had experienced that the Bantam front brake worked better in reverse than it did going forwards!

Whereas I had noticed this, but never at that time thought too much about it, naively believing BSA and others had thoroughly developed their products over the 50 years plus of manufacturing motorcycles to be efficient and exemplary examples of engineering excellence; he found out that if the cam rotates in the opposite direction to the wheel motion, braking mechanism efficiency is greatly enhanced!

https://www.youtube.com/watch?v=bbScxZsBhPQ

Why didn't the Factory's find this out and if they did why didn't they do anything about it?

So in between working I will be combing YouTube for ideas and examples of innovation!

I think Howard Robinson put a photo of a modified brake cam lever on a Dominator he has, if i remember rightly the brake plate is rotated and the cam lever does indeed rotate the reverse way to the wheel motion when going forward!

Cheers

John H

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Re: SLS brakes forwards and reverse. A SLS brake has one leading shoe and one trailing, and this is true whichever direction the wheel rotates since the shoes swap over their roles.

If it had new brakes the Bantam, or any other SLS brake, would have the same retardation in reverse, but because of the direction of travel the wheel would lift off the ground and skid more easily, giving the impression of working better. This equal effect assumes that the cam is symmetrical.

However, over time the leading shoe wears more leaving the trailing shoe being an effective limit on the pressure applied to the leading shoe. If you then rotate that worn brake in reverse the less worn shoe can exert its full leading effect.

With a twin leading shoe going backwards both shoes are now trailing. It is noticeable that a TLS has an absence of bite when wheeling in reverse.

Norm

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I haven't read the book but am of the firm opinion that SLS brakes in which the operating lever opposes the wheel rotation (eg Velo Venom) have a much better braking effect than those where it trails (most Nortons).

This is because in the "opposing" setup the leading shoe is pushed outward by the inner portion of the cam. As the effective distance between this and the shoe pivot is smaller than that between the outer portion of the cam and the pivot, the leading shoe moves further for the same rotation of the cam spindle. Of course, there is the usual trade-off that the force applied to the shoe is slightly less. In the "trailing" setup the reverse applies.

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Another complexity: After a period of time, both shoes in an SLS brake still sit in contact with the drum. Therefore the system forces them both to wear at the same rate. Therefore they must both have the same braking effect. Since we know the TLS is much worse (hopeless!) in reverse, it then means that the SLS brake effect will be exactly half way between the effect of a TLS brake going forwards, and a TLS going backwards.

And I'm sure Norman is correct - reversing the lever might well cause an immediate improvement to an SLS, but it would then revert to average shortly after since both shoes must exert the same force.

The twodrawbacks of TLS are the poor braking going backwards (take careon a steep hill...) and the self servo effectcan be dangerous, especially for the first few applications after it's been standing for a while in a damp shed. And (of course) adjusting it - but that sorts itself out in the end anyway.

But there is discussion elsewhere on this forum including from someone who seemed to have design experience of drum brakes (not I).

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I find that swapping the shoes round regularly on the SLS is better than leaving the leading shoe to carry the wear. Its also true that re-arranging the lever to move in the oposite direction makes the brake work better. I think this is down to the altered leverage ratio that comes from changing the position of the striking point of the cam on the shoe ends. I think that the trailing shoe is then sharing the work better than in the standard set up.From my regular checks with a vernier caliper its clear that the trailing shoe is only doing a fraction of the work on the standard brake.

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I have had a 2LS hydraulic rear brake fitted to my Commando for many years now. Initially it had a flat alloy brake plate but this wasn't up to the job. The brake internals were from a mini and a proper mini back plate was used in the end. The master cylinder was from a triumph herald and is now from a Honda CBR 600. I'm not sure what car brakes were 8" or even 2LS but Rod Thompson mentions a Morris Minor item. A car master cylinder of that period was normally about 7/8" dia. a motorcycle front brake master cylinder of about 13mm should give a good mechanical advantage but the shoes will have to be close to the drum to avoid excessive lever movement to bring the shoes into contact with the drum. I think a centre boss will require turning to centralise the brake plate and take care of the lateral position, this will need welding into the plate and also some kind of torque arm or pin incorporated into the plate. Careful positioning of the torque arm will give access to the shoe adjusters ( i.e. not hidden behind the fork leg or mudguard stay) and minimise the length of hydraulic hose needed.

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In the 70s, a friend of mine noticed a Hillman Minx in his street with its wheels in the air. That it had 8" tls hydraulic front brakes. He removed the right side brake plate, and offered it up to the front hub of his late 50s Mod 50 Norton. Not sure if it was the '55-7 half iron, or '57-on all alloy. The plate went in, he found a suitable spacer between bearing and plate, and plate and fork leg. A pair of large nuts, it you please. He took the lug from his Norton brake plate, and a master cylinder from a Yamaha he had junked a while before. The expensive part was the brake hose to connect Japanese master cylinder to British slave cylinder. It worked

I rather like the idea of a late '60s BSA / Triumph 2ls plate. Has anyone fitted one to a Norton fork / hub setup?

Paul

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Someone has on Facebook, he sent me a picture, it is as you identify with, 1968-1970 BSA/Triumph unit fitted in to Dominator forks!

I have a search through see if I can find it!

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I converted a Triumph single leading brake to twin leading fully floating in the 70's. Using single side cams with radius backs used as the pivots, attuating arms pulling together with inner and outer cable.

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Previously christopher_winsby wrote:

I converted a Triumph single leading brake to twin leading fully floating in the 70's. Using single side cams with radius backs used as the pivots, attuating arms pulling together with inner and outer cable.

How much of an improvement was the set-up?

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At the time it was good but I was using racing linings so you had to get them hot. It was only a 7 inch drum single leader to start with with normal linings which use to fade. Fortunatly there were lots of soft grass banks and ditches around then. I should have slowed down, but I was a teenager. The Triumph also had the early swinging arm fexi frame which made for interesting handling. No where as good as the 69 Bonneville I have now but that is better than some early disc brakes.

Obviously an 8 inch drum would be better, disc brakes are the way forward for better brakes but drums look better.

If you email me I can send you a picture of the bike, not pretty but it went well.

cwinsby@hotmail.co.uk

I cribbed the idear from one I saw but cannot remember where.

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Cheers I will do just that!

Someone warned me if you put your email up, write AT/at rather than the @ sign, as it stops "Spam Bots" from picking up your email address!

Cheers

John H

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Previously john_hall1 wrote:

Cheers I will do just that!

Someone warned me if you put your email up, write AT/at rather than the @ sign, as it stops "Spam Bots" from picking up your email address!

Cheers

John H

Thaks for the email warning.

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I have converted an 8 inch norton single leading backing plate ( later type ) to a twin leading set up. Basically I created a 1968/70 Triumph set up on the norton backing plate. I used 8" triumph shoes cut down 5mm on each side, Triumph spindles and springs. I built up shoe abutments, moved the anchor point for the cable and the backing plate to fork slider. I have followed the Triumph dimensions for the activating arms and clevises.

All seems to work well as a bench test. I will soon put the backing plate into service on a friends feather bed ES2. If it is a success I will strip it down, take some pics for anyone who has many spare hours in their life.

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Previously andrew_westmore wrote:

All seems to work well as a bench test. I will soon put the backing plate into service on a friends feather bed ES2. If it is a success I will strip it down, take some pics for anyone who has many spare hours in their life.

Even if it's not a success, some photos would be great, so please do take a few.

I have been toying with the idea of making my single leader into a fully floating brake by using triumph shoes and a modified pivot point, but the plan is on the back burner during the riding season.

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I have attached a couple more images of the backing plate which might prove helpful to you with your project. I am having problems testing the brake, I will have to look into getting another bike with the right front hub.

Attachments BILD1641.JPG bild1642-jpg
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Back again! It has taken time to fit and test the brake on my friends ES2. I have ridden about ten miles around the suburb where I live, working the front brake to bed it in. Considering such a short period I would say it has been a successful exercise. It seems to be on a par with the standard Norton twin leader at the moment but it is early days yet.

I am hoping that once run in it will perform as well as the Triumph twin leader it is based on. Once bed in I should get the same servo response that I get on my S8 Sunbeam which has the Triumph brake. The servo effect is very strong on the Triumph brake. This is because the self centering has a wedging effect on the shoe at the opposite end to the cam end. Hopefully when the brake is bedded in it will require less effort on the brake lever which is the case on my Sunbeam.

Attachments bild1656-jpg
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I don't really wish to be the harbinger of bad news but looking at the photo of your front brake has serious alarm bells ringing for me. In a normal set-up the top and bottom levers should be nearly parallel to each other in terms of relative position. Any position much different from this generally indicates an incorrect adjustment or badly worn drum. It looks to me like you only have one shoe actually doing a decent job. I suggest you use the search box (top left) to check out tips & hints on TLS adjustment.

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Previously ian_soady wrote:

It does look odd but it depends on the cam profiles.

When I built this brake I spent a lot of time making sure it would perform and be SAFE. When I made the actuating arms I spent less time as I figured that it wasn't worth spending hours making them if the brake didn't perform.

When triumph made the arms they would have used a jig and a stamping machine to make the square hole which locates on the square end of the cam spindle. I used a hacksaw, drill and a file. I wasn't too fussed about the accuracy as I intend to make new ones which will be a copy of the shape of the Norton arms. These will be parallel and polished.

So although the set up looks wrong, I have set up the linkage so as the two shoes hit the drum in unison. The bedding in process will ensure this as it is likely that one shoe will be ever so slightly ahead of the other.

 

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