Forum

[The rider formaly known as Lone Rider]

Can someone come up with a simple mod? The way I see it, as do most others, it is uneven pressure from the shoes.

So - what if the brake cam operating levers were the same length, and then route the front brake cable so that the inner cable pulled up on the lower arm, and the top arm was operated by the outer cable being drawn downwards when the brake is pulled on. That will make it self centering in its operation. Just saying.

[papasmurf]

"Can someone come up with a simple mod?" Fit a disk brake. As has been pointed out setting up a twin leading shoe brake system is a black art. You need to be scrupulous. I am a bit puzzled by the 90% arm issue. The brake arm should not go past the 90% angle when your knuckles are bursting through the skin, if it does you are loosing braking effort.

[Paulk]

A simple mod!! Now this is just theory so bear with (please). Would it be possible to do away with the parallelogram all together? I'm thinking of BSA/Triumphs conical hub arrangement whereby parts are changed to so that instead of having to set up the brake the cable pull does it all automatically all the time and is self adjusting. For those not familiar it's two equal length brake arms where one act's as a stop for the outer cable and one has a nipple for the inner cable in the normal manor. Then on operation both brake arms are pulled together and the same pressure in applied to both brake shoes. Okay there's a slight difference because of the depth of the cam but anyone tried it?

BTW - on the assumption that all parts are good etc should not Tim's and Hitchcocks' methods produce the same result? Is not the Hitchcock's method just an other way to get the parallelogram?

[Paulk]

Leon, Just a thought but have you checked that the rear brake spindle can float on the brake plate? Mine was seized with paint from new. I hadn't realized that Enfield rear brakes are somewhat different to other makes in that you don't apply the rear brake and tighten up the spindle (you can't) to centre it, it does it automatically - providing the holder can move in relation the the brake plate.

[John L]

First off, I must say that my general performance expectations of my Bullet 500ES and Redditch 350 Bullet probably differ from those of most of the contributors on here, and as a result my experiences with them has often been at odds with the general concensus.
However, I find myself agreeing with what TimNZ says - well most of it, anyway.....
One of the first problems I encountered with the TLS brake soon after buying the 500 was that the cams seize VERY readily in the backplate;
this brought to my attention that the "reversed limk rod" mod. had been carried out by the PO - and the foolishness of such a change, as it allowed the upper cam (which was partially seized) to stick independently of the lower cam. So much for "easy adjustment"......
After servicing the brake thoroughly and weighing up the pros. and cons. I put the brake back to standard and carefully set up the adjustment in much the way that TimNZ outlined - with an immediate improvement. After several more miles of bedding in this brake then revealed itself to be a perfectly adequate performer. BUT (there has to be BUT, doesn't there?) The problem of the cams sticking reared its head again after what seemed to be an unacceptably short time. (Please don't anyone suggest I should have used copperslip or WD-40, etc.) Also, I tried one of our host's HD cables, but found it awkwardly bulky and inflexible. A further point that no one seems to have mentioned is that the brake outer cable stop/adjuster is on the fork slider - this means that every application of the brake is attempting to twist the brakeplate around the wheel spindle (even while stationary) - add to this the torque applied when braking from speed and you have an explanation for why the brakeplate nut needs to be so bloody tight to prevent regular loosening. Has no one else experienced brake plate flexure, either ? (Just like the g/box outer blight that EVERYone moans about).
Other experiences, and other opinions are out there....

[Tim NZ]

The post 1970 BSA/Triumph COMICAL front brake was a JOKE: it IS NOT a twin leading shoe brake: The push pull cable results in a 1 trailing shoe 1 leading shoe, with no servo advantage. Its only redeeming features were the micam adjusters and the floating shoes.
Who ever designed it, or sanctioned its fitment needed to be shot with a ball of their own excretement! The design was originally intended to be a hydraulic application but that was going to be too costly, so BSA ‘fudged’ it with a silly cable operation.
Cam pivots need a metallic lubricant to prevent galling/seizing. If the taper faced nut of the axle is coming loose then the axle is not correctly spaced out; shim-up the nut to be hard against the fork leg.

[Tim NZ]

H's adjustment method maybe acceptable to Joe Average who does SFA miles and is happy to be continually resetting the brake levers.
For each degree of divergence between the two applied levers, the loss of applied force to ONE shoe changes in a compounding fashion: the greater the divergence from a true parallelogram the greater the loss of efficiency. Set the link rod to anything other than true and square and every time you reset the levers the brake GETS WORSE!
REALLY REALLY!!
Yes, for a brief moment in time the brake 'feels' better than it was prior because both shoes are brought back into contact, but the true effect is the opposite!

[another Allan]

Hi Tim. How is the 'comical' brake not a TLS design? The brake cams rotate in opposite directions, but each one bears upon the leading edge of its corresponding shoe, surely? Regarding the Enfield TLS parallelogram you have described, the geometry argument sounds correct, and when I have put my Bullet's head back on, I'll give your suggestions a try. However, given Indian manufacturing tolerances, what are the chances that every Enfield TLS brake in use can actually be set up as you describe? Have you found any examples where it would not work, due to variations in cam spindle hole positions, for instance?

[Bullet Whisperer]

I have stayed out of this one for as long as I could. I recently restored a BSA Rocket 3 MK II and personally rebuilt the wheels, as well as everything else. The conical front TLS brake received new shoes, cable, etc and the wheel could be locked if the lever was pulled hard enough. Nothing wrong with the conical TLS, if set up right. The 7" SLS front brake on our 350 Clipper racer can raise the rear wheel off the deck from high speeds, if applied hard enough unless it gets overheated during a race and fades a bit. If everything were perfect, the TLS on the Enfields could be set up using trigonometry, symmetry, geometry, etc. This is fine if you can get the brake plate into a lathe, fitted with oversize linings, with the brake levers pulled 'on' very slightly and machine the linings to the same circumference and diameter as the drum. This way, when the levers are let off [I cable tie mine into a slight 'on' position for machining], the brake plate will fit into the drum with the shoes just clearing until the brake is applied, when full contact will be made by both shoes, for maximum stopping power. I tighten the spindle / brake plate nut with the brake applied and before fitting the wheel to the machine. My Enfields stop very well, by the way. My 2p. Paul.

[Tim NZ]

The BSA designed comical brake has one shoe advanced by the trailing edge of its cam, the other by the leading edge; it 'looks' like a TLS, but it isnt. Both shoes ‘lead’ but off different faces of the cams and thus applied pressure is not the same.
One of the the biggest ever flop of a brake on the race track...

The Indian 2LS is fine and its manufacturing tolerance/variance not that great; it just needs to be accounted for. What one has to keep in mind when setting the leavers is to take all dimensional checks with the levers fully loaded. Simply setting the levers to 143.5mm centers is fine to start with, but there is a wee bit of slop at the trunnions that must be accounted for. Occasionally one may have to reverse the cams, or swap them over to optimize alignment of the splines on the actuating levers. Occasionally I have to lightly file the heel off a shoe.
Want to potentially distort your brake plate? Apply greatly differing pressure to each shoe. You may not see any distortion at first, but the load across the plate from one shoe doing more work than the other, and one shoe running hotter than the other will eventually cause problems if not checked. In a typical SLS brake the trailing shoe has about half the applied load, and the peak heat generated is at around a 4-1 ratio, Leading/Trailing: Heat = Wear. One shoe wear faster…
Check the Enfield rear brake plate after a year or four where the cam housing has not been reset? One shoe will be worn out and the rear brake plate most likely warped. ALWAYS centralized (apply) the brake prior to tightening the Axle nut, and in the case of the rear brake, the torque stay nut too.