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[Old Plonker Mike]

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

[Felix]

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.

[ric]

I've heard from several people mention the night and day difference after having oversize brake shoes fitted and skimmed in PriceParts workshop.

[binary]

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.

[Tim NZ]

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.

[Alan R]

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..

[binary]

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.

[neddy]

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.

[Old Plonker Mike]

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.

[Felix]

I forgot to mention my rear brake is hampered by the horrid right-hand Merikun linkage.
You Brits were spared that indignity. Someday...