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Work is continuing on bringing my 1970 Lightning out of its' 42 year hibernation. As I disassemble everything (working on the rear of the machine, I am cleaning thoroughly and polishing everything, being sympathetic to the patina of a 50 year old original machine. She is certainly looking much better, and helps to motivate me on. Anyway, the questions at hand-

The brake cam lever on the rear drum is positioned Up at a 2 o'clock position instead of down as most I have seen in pics, my '68 Thunderbolt as well. Is there a preferred position? While this would move the shoe cam in the opposite direction, it would simply shift the leading shoe from one to the other. Any reason for me to change it back?

Also, any tips on removing the brake springs? I have always used Vise-grips and a screw driver to pry them away, but these buggers are tough!

Thanks!


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1968 Thunderbolt
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In the start of the 70 production bsa fitted a shorter torque stay and mounted the arm the other way up to give a more effective break, sadly the short arm had a tendency for whipping up (presumably moving the wheel back also???) and causing the brake to lock on. They reverted Back to the earlier style with the longer torque stay and down mounted lever.

If you wanted to get fancy you could change the internals, fit an oif cam, match it with the arm and have a fully floating SLS rear brake which will be much better than the pre oif models yet looking almost exactly the same.

With this some levers and cams are for downward use and some upward, notified by a square section for downward arms and square with rounded at 2 sides for upward arms. This replaces the spline on earlier pre oif models.


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68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Very interesting! As having the brakes lock on would be disagreeable, I like the notion of the OIF brake cam. Are you also suggesting the OIF torque arm? Any additional specifics on this would be great. I'm all for a functional improvement while leaving its' appearance the same.

I'm fortunate to still have a local British cycle shop (not much activity there anymore, but the owner is an enthusiast from wayback, and would rather spend his days there than watching TV) that has a good stock of used parts.


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1968 Thunderbolt
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if you have the one with the leaver arm facing upwards and the shorter torque arm Allan is talking about BSA actuality put out a service sheet (recall notice ) about that ie changing it to downwards arm and longer strap ( i cant find it atm but its a fact, will try to find the service sheet number latter)

you dont have to change the cams , but you DO have to change the external return spring to the standard one


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I’ve probably added more confusion than help at this moment.

Otherwise ignoramus says.


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68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
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Lever up or down, changes the top to toe relationship of the cam to the pads, the forward shoe is the leading shoe, if the lever is down , when it is pulled forward the toe of the cam operates against the leading shoe, since it is at a minor diameter compared to the top it gives a slightly more sensitive feel, .
Conversely with the lever up the top of the cam at the major diameter is pushing the leading shoe.

None of this matters much, what really matters with the back brake is the amount of pad material on each shoe,

the leading forward shoe has a reduced surface area, the leading edge is cut back at least an inch compared to the trailing shoe, dont mix these up,( this isnt mentioned at all in the Manual, my bike still has its original shoes and one definitely has more material than the other, I think its covered in the Rupert Ratio book) if you get them relined make sure you follow the original layout, or you will have a grabby brake with no feel.
My 71 has the lever down, my pals later bonnie had the lever up the brakes felt about the same.

To remove the brake springs/ shoes lift/ pull out and up against springs a bit, the end of one shoe out of position and upwards so it is no longer located, springs will now be slack, refit the same way.

Last edited by gavin eisler; 07/14/20 8:31 pm. Reason: punktchooatshun

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FYI
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my '70 a50 has the short arm and upright lever. as far as the plate rotating cw when braking, there is a protruding squarish bolt that would hit the swingarm if it tried to rotate.

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thats the one i was referring to AML well done saving me looking for it

the other issue with the facing up arm is that as the wheel is moved back or forward adjusting/replacing chains, it does things to the geometry with the short arm

besides all that technical stuff the arm facing upwards looks silly


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Having the brake lever up at 2 o'clock vs down at 8 o'clock makes a difference to the efficiency of the brake and this is why some people convert their front single leading shoe brakes so that the lever reversed.

The reason for the greater efficiency is because the brake cam wedges the leading edge of the shoe against the drum surface which causes a self-energizing “servo” effect, causing the leading shoe to be more tightly pressed against the drum. Whilst this effect is great for front brakes, rear brakes don't need to be as efficient and its generally thought that front brakes provide at least 75% of braking power whilst the rear needs much less.

I don't know why BSA moved the brake lever to the 2 o'clock position and then changed it back. I've always had my rear brake levers in the down position which probably makes the brake a bit smoother and less likely to grab.

Regarding removing the springs what you could try is pushing the cam and pivot out from the brake plate with the shoes attached. Once the cam and pivot are removed the shoes should literally fall out.

Last edited by gunner; 07/14/20 8:05 pm.

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1967 B44 Shooting Star
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Thanks for al of the information guys! I spent some time yesterday studying the 1972 OIF brakes, thought about my options and decided to just go with the longer brake anchor strap and the appropriate spring to put the lever in the down position, as suggested in the BSA service bulletin. I have the parts at hand, so made the decision easy.

I got the brake springs off using vice grips and a screw driver without drama. I tend to go pretty easy on things in an attempt not to destroy anything I am working on, the springs just required a little more effort. The fun part of this for me is taking everything to bits, cleaning, inspecting and getting it back into "as new" condition. So far, very pleased with most everything i have encountered. The rear fenders on these are a bit flimsy, there are a few cracks around the stud where the brake light mounts. Working on some reinforcement for that too.


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Back to the well. Ready to reassemble the rear brake, and wanted to get your opinions on lubing the cam faces and pivot. Thanks!


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Originally Posted by ChiefRider
Back to the well. Ready to reassemble the rear brake, and wanted to get your opinions on lubing the cam faces and pivot. Thanks!

Yes, this should be done. Use nice sticky axle/bearing grease as it is the least likely to come off and get where you don't want it.


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'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
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I've recently been using Silicone grease with PTFE on brake cams and spindles, seems to work well as its water-resistant and copes with high temp. see This link for example


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando

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