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2LS Front Brake

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2LS Front Brake
Started at 03:59pm on the 11th August, 2017 by Old Plonker Mike
Old Plonker Mike Subject: 2LS Front Brake
I am struggling to get enough braking effort from my front twin leading shoe brake on my 500 Enfields. I read the previous post where Tim suggested that a correctly set up TLS brake could be perfectly adequate (and I see no reason to dispute that). Back in my world, with two of these brakes fitted to different bikes, I am strugling to get any serious stopping power. The story so far - I bought new relined shoes.(Hitchcocks improved type) I bought a new, later, "improved geometry" brake plate. I carefully set up the linkage making sure both shoes are activated together, and a near square angle is presented between the lever and the cable. I rounded and polished the cams, as the sharp corner often digs in to the plate on the shoe causing friction and wear. In desperation, I tried removing the link mechanism all together and constructing levers so that the outer cable terminated on the upper lever, and the inner cable terminated on the lower lever. This provided extra braking (by doubling the mechanical advantage, and thereby lever movement) this required very close adjustment, which revealed that my drum was not round. Sadly this experiment also explained why this simple arrangement is not used. There is no self centring for the brakes in the off position, which results in one shoe always dragging on the drum and gently cooking it. I fitted a new wheel. I fitted a new stainless brake linkage and set up nicely I wondered about friction in the pivot bearings, so fitted needle rollers in the pivots. The previous thread mentioned turning the shoes to get a better fit, so (not having a handy lathe) I removed the shoes, spotted the high spots from wear, and gently filed them away. Refit the shoes and use heavily for several miles. Remove and repeat process until a significant proportion of both shoes show marks from contacting the drum. Take on a 100 mile run out in the hills to bed in. net result the front brake still feels dangerously inadequate and the tendons in my forearm are beginning to strain. I believe that a brake this size should be capable of locking the front wheel. (maybe not repeatedly in short succession, but once at least). I had a similar problem with my Bonneville disc brakes, until I found appropriate pads and this will now lock the front wheel at any speed with two fingers on the lever. (also now very dangerous after spending a day riding an Enfield) I can only think of one explanation, and that is that the lining materiel does not have a high enough coefficient of friction. I believe that with any given geometry on a leading shoe there is a maximum coefficient of friction, at which point the servo action just locks the brake on, but I don't believe I am anywhere near approaching that point. Does anyone know please what materiel is used for the Hitchcocks "improved" shoes ? or what coefficient of friction it has ? Does anyone know of a materiel with higher coefficient of friction ? Does anyone know where shoes with this can be obtained or constructed ? I am guessing that racers might use compounds not suited to road use ? Many thanks, Mike
Posted: 03:59pm 11th August, 2017
Felix Subject: 2LS Front Brake
You've done many of the things I tried in order to improve braking. I still haven't found braking nirvana but did get some edge by using our host's HD English made cable and fettling the rear brake with a long arm to increase braking. I think the addition of the arm helped the rear a bit,and I used new Indian rear shoes and arced them with an abrasive glued into the drum. I'm used to double disks on my other bikes and seldom use the rear, but with both brakes and compression braking I seem to stop fairly well. I did find the Hithcock pads better than stock pads.
Posted: 05:51pm 11th August, 2017
ric Subject: 2LS Front Brake
I've heard from several people mention the night and day difference after having oversize brake shoes fitted and skimmed in PriceParts workshop.
Posted: 06:54pm 11th August, 2017
binary Subject: 2LS Front Brake
Look at Hitchcock's "Technical Notes", they have a good lot of information on the setting up of twin leading shoe front brakes. Your twin leading shoe brakes should work almost as good as a disk brake when set up properly.
Posted: 11:40pm 11th August, 2017
Tim NZ Subject: 2LS Front Brake
If ANY mechanical Twin leading shoe brake is set up with its leavers in ANY configuration OTHER than a perfect parallelogram, (true & square) it WILL NOT be operating efficiently and will only progressively worsen.
No disrespect to our host, but their instructions for adjusting the TLS brake by randomly setting the link rod, whilst well meant, is highly erroneous and seriously misguided.
The effects of so adjusting a Mechanical 2LS brake will be short lived at best.

To locate a better liming material you may want to talk with several SUCCESSFUL classic bike racers, and find out whom and what they use? Be aware that linings that are #1 for the track and not always so good on the road...
The main thing is to find a reputable technician.
You may also want to consider obtaining a spare brake plate, one that can be used (modified) as a basis for a lining radiusing jig?

Correctly arced linings, no matter what material, will perform better from new and for the duration of their service life, than a 'pair' shoes that had seen one shoe over-heated and/or glazed as a result of initial misalignment.
Correct initial bedding-in of lining-to-drum as a result of progressive application is critical.
Posted: 12:27am 12th August, 2017
Alan R Subject: 2LS Front Brake
Hello OLD PLONKER---- I'm going to visit "The Dark Side" now and speak the unspeakable }----- so why not convert to Disc ??-- at least on one of your machines ??.......If it's the Iron Barrelled 500 Classic you have then the Disc wheel assembly can be a direct replacement ( With a small amount of sawing and filing )...I've done one a few years back and am part-way into my current bike.....However if it's the "look" of TLS that you prefer then soldier on...I fitted a 7", full width, 2L/S conversion plate to a 1960's Triumph 650 Thunderbird years ago and that nearly folded the fork legs from under me !!... so it can be done..
Posted: 12:51am 12th August, 2017
binary Subject: 2LS Front Brake
I do not think that the Hitchcock's Technical Notes on twin leading shoe brakes are "highly erroneous and seriously misguided", as some others on this forum have commented. Hitchcock's information has been a great help to the thousands of Royal Enfield owners all over the world. There are plenty of restorers of other British motorcycles that envy the help and the parts backup that we get from Hitchcock's. I appreciate all the help that they have given to me over the years and I have never been disappointed by there 100% service and help.
Posted: 11:25pm 12th August, 2017
neddy Subject: 2LS Front Brake
For myself did the Hitchcock mod. to the brake linkages, did not find it any easier/better and put the system back to how it was made, think the system should stay as it was designed.
Posted: 09:57am 13th August, 2017
Old Plonker Mike Subject: 2LS Front Brake
Thanks for all the responses. I am happy with the geometry. I set it up quite carefully off the bike, and both shoes operate together as intended. I like the idea of abrasive fixed inside the drum as a DIY turning arcing method. I think I will give that a blast. I don't think it will make it worse. I am intrigued with mention of the back brake not working very well, as mine is quite vicious, and can be locked without much effort at all. This is one of the things that persuades me that the front brake ought to be capable of delivering serious stopping power. Everyone seems to agree that the brake should be capable of serious stopping, so I am encouraged to continue trying to improve it. I have a spare backplate, but I think the arcing or turning process is beyond my shed capabilities except for Felix method. I know I could swap to disc brakes, but that feels like giving up and I would really just like these drums to work. My Bonneville was as bad with its disc (and twin discs after I modified it to get more braking), until I found a couple of manufacturers making pads that worked properly on iron (not stainless) Ferodo and Dunlopad provided good but quite different materials for that, and the difference was astounding. I was at a vintage fair at the weekend, and found myself looking at BSA and Honda TLS brakes. I have noticed quite a lot of difference between sets of shoes. I have one set that will barely fit in my drum, and another that fits in easily and needs a lot of cable adjustment to get contact.
Posted: 03:27pm 13th August, 2017
Felix Subject: 2LS Front Brake
I forgot to mention my rear brake is hampered by the horrid right-hand Merikun linkage. You Brits were spared that indignity. Someday...
Posted: 10:40pm 13th August, 2017
another Allan Subject: 2LS Front Brake
Hi OPM. Are you saying that you found that the drum was oval, so you addressed this by filing the shoes, or have I misunderstood?
Posted: 08:41am 14th August, 2017
Mark B Subject: 2LS Front Brake
The 2LS brake on my 500 is very effective. At the risk of explaining how to suck eggs etc, if you hold the brake firmly on when you tighten the nut on the spindle that will ensure that both shoes are as well centred in the drum.
Posted: 01:37pm 14th August, 2017
PeteF Subject: 2LS Front Brake
Mark, the front brake plate doesn't float so how can your method work. Am I missing something?
Posted: 02:39pm 14th August, 2017
Old Plonker Mike Subject: 2LS Front Brake
Hi Allan, I replaced the front wheel to deal with the out of shape drum. I filed high spots off the shoes linings to make them fit the drum better (same idea as arcing/turning, but slower and using a file and no big micrometers). Mark, I am happy to be reminded of the simplest of things in case I missed one. Often I find a mistake that I just cant believe I could make. I can be a bit overenthusiastic (or impatient as other people call it). In my investigations into brake material, I have found Ferodo 2520v which seems to have everyone raving over it. I read the friction graphs and it looked good, but then much the same as everything else Mu values between 0.4 and 0.5. It is usually the high temperature performance that people are after, but its just the first bite that I want. I am now looking for someone who will attach it to some shoes (preferably with glue and not in the USA). I just contacted a chap who tells me this is no longer used, but he can do all the fitting work and has material he trusts, so I will visit him and get some shoes made up and turned to fit my brake plate and drum, and see what happens.
Posted: 02:43pm 14th August, 2017
Mark B Subject: 2LS Front Brake
It certainly improved the 2LS shoe on my Morini dramatically, so I did the same thing when replacing the front wheel on the Bullet; as that brake was working very well anyway I probably made no difference to the set-up...
Posted: 02:44pm 14th August, 2017
another Allan Subject: 2LS Front Brake
Thanks for the clarification, Mike.
Posted: 07:41pm 14th August, 2017
Alan R Subject: 2LS Front Brake
Hi Guys---------Mention of dear old "Moo" ie}----Mu, reminded me of far-off Apprentice days including slow Brit bikes ( for an L driver that is )..."Fast" girls and a rapidly evaporating pay packet ( once a week---in a Brown paper envelope )....We must remember that it is a constant figure for the Co-Efficient of friction between two materials....a change of either materials yields a new Mu ............If the drum is oval then it's the drum that needs to be rectified first--- either a new lining or the existing one turned and trued to a concentric setting.....The overall diameter will have changed so new, oversised shoe linings will be needed here...then machined to match the new Drum dia..
Posted: 10:38pm 14th August, 2017
Old Plonker Mike Subject: 2LS Front Brake
Well, I now have my relined shoes, with nice sparkly black linings courtesy of the nice man at classic brake services at Whaley Bridge (which also afforded me a nice drive out). It was very noticeable that after arcing/turning one shoe's lining was much thicker than the other. This seems to indicate some notable tollerance issues with my brake plate and or shoes. This will probably explain why arcing or turning is more important to some people than to others, depending on how the tolerances add up in your brake parts. I have also realised that it is not clever to shuffle the brake parts, and need to mark them all up so that the shoes always return to their matched brake plate and always in the same position (or better still don’t take them off). Braking is improved (even though I was not sure at first). After a hundred miles or so of bedding in on just normal use, I noticed that I am only using two fingers now for braking, and not straining all the tendons in my forearm. I am also pulling up early at junctions, always a sign of good brakes. I noticed that I am nearly bottoming out the front fork too, but think that is more to do with nice new soft springs. I think both my new linings and the ones from Hitchcock's like to be warmed up a little. I find them both unenthusiastic at first, but after a few miles of use they seem to perk up a bit (unless it is me getting used to heaving on the lever). I have managed to provoke a squeal from the front tyre (its only an SM), so I think I have a brake now that could lock the front wheel. In answer to MarkB and PeteF, I appreciate that the front brake is not designed to float, but if you release the locknut on the brake plate you will likely find a generous amount of "float". The procedure from MarkB is useful to make sure you start with the brake in its optimum position. I suspect that the braking forces might be enough to re-arrange things anyway, but no harm starting out with it in a good position. Fractions of a millimetre do count (as do whole ones). I feel much safer now, so thanks to all. I will update if there is any further development over the next few hundred miles, but I seem to have a functional brake now.
Posted: 11:06am 30th August, 2017
stinkwheel Subject: 2LS Front Brake
I actually DO leave the brake on my 350 bullet slightly floating after experiencing extreme frustration with the braking efficiency. Allowing it to effectively self-centre moved it from dangerous to adequate.

I simply backed off the dome-bottomed pressure plate retaining nut about half a turn from fully tight. I fitted it with threadlock and when I fit the front wheel, I pull the fork legs together tightly against the wheel nuts using a camlock strap before nipping up the clamps. There is no way it can come undone like this.

The one thing that made most difference to mine was changing the lever. I'm currently using an upside down clutch lever assembly off a GPZ500s instead of the standard brake lever. It's span adjustable and has the pivot/fulcrum located further from the bar giving much more leverage. The clutch idiot switch makes a way more effective and reliable brake light switch too. Standard barrel nipple fitted right in with no alterations.
Posted: 04:55pm 30th August, 2017
Old Plonker Mike Subject: 2LS Front Brake
Stinkwheel, thanks for that, I am glad someone else found the "float" useful. I have been considering rearranging the brake plate to make the "float" available/useful. I might also look out for a GPZ500 clutch lever. I have a couple of issues with the front wheel design at the mo. The tolerances on parts are seemingly very free. I have two bake plates that differ in thickness by 2-3 mm at the point that they are clamped by the cone shaped nut. Fitting the thicker of the two requires the forks to be splayed to get the wheel spindle in, which will not be good for fork performance. I cannot understand this design with the clamping nuts (speedo and brake plate) butting up against the fork legs. My Bonneville for example has a reference surface (nut) on one side of the shaft that is pulled up to the fork with a nut outside the fork, accurately setting the position of the wheel relative to that fork. The other fork leg then clamps on to the spindle where it touches, ensuring no stress or bending in the fork legs. With the Enfield design, I see no problem if there is clearance between the fork legs and the clamping nuts, but if the nuts are touching, it surely guarantees misalignment of the forks. On the plus side, I was taking out my machine with the new brakes, and faffing about with some carb tuning, and the engine misbehaving a bit, I was trying to pull out at my road junction and got a bit flustered, and ended up grabbing at the new front brake, which firmly planted the fuel tank into my nuts. I take that to mean the front brake is now working very nicely. Thanks to all who contributed.
Posted: 12:18pm 6th September, 2017

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