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by Mal Marsden - 06/16/22 7:00 pm
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Allan G, johnu, NickL, OriginalScott
Total Likes: 9
Original Post (Thread Starter)
by johnu
So I built a 1974 B50mx to race in vintage mx and I love the bike but the front brake is miserable. Now I am use to modern mx brakes so I don't really have anything to compare it too but I still feel it should be better than it is. I had the brake shoes relined when I built the bike up and the drum all looked good. I also think the angle looks ok on the brake arm so I don't really know if there is anything else I can do. Like I said I love riding the bike but with the way the front brake is I don't think I can race it like that! Any help would be appreciated.
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Liked Replies
by kommando
That arm at rest is in the wrong position, when the hand lever is operated the arm angle to the cable should still be over 90 degrees. It won't make much difference but worth trying turning the lever over if the hole is serrated and engaging it further back so it pointing to the ground more.


With the lower use of imperial thickness linings the aftermarket is using metric thickness and fitting say 6mm thick instead of 1/4" thick linings, so you start with new shoes with 1/2 worn linings which also only touch on one end.

So what brand shoes did you buy ?

This is why Villers services and Saftek are the go to places for shoe relining, the lining thickness can be custom or the OEM imperial thickness.
1 member likes this
by triton thrasher
triton thrasher
This is not a recommendation. Modifying your brakes can be dangerous.

On this Norton backplate, lining material has been removed from the trailing end of the trailing shoe, by a mad experimentalist.

It allows the cam to put more pressure on the leading shoe, instead of the cam being stopped from turning by the trailing shoe contacting the drum. That cam jamming effect is a characteristic of non-floating SLS brakes, and ones that float the wrong way.

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1 member likes this
by Peter Quick
Peter Quick
In the picture where we can see the brake cable entering the lug that holds the cable ferrule there might be a problem. It appears that the ferrule on the end of the cable barely rests on top of the lug. It is supposed to fit in the lug its full length. The ferrule at the end of your cable is too big in diameter. I can imagine your cable popping off the lug in its present precarious situation and then there would be no front brake. Or is your ferrule a stepped set up where an equal amount is inside the lug? I just can't tell from the picture.

The free play on a correctly made cable is 4" (take off the adjuster at the lever end first!). Does your brake cable have an in line adjuster (it is supposed to)? I can't tell from the picture. I just looked at my B50MX and the brake lever on your brake plate looks about right for its placement, so that isn't your problem. And like others have said the arc of the shoes may not match the drum.
1 member likes this
by Mitch
getting drums turned and/or relining brake shoes will almost certainly result in a miss-match. you may only have 30% contact. shops used to have a machine to grind brake shoes to match the drum but it is very hard to find someone that does it anymore. there are home remedies, some as simple as putting sandpaper in the drum and working the shoe by hand. there are also some home made machines and fixtures. plenty stuff on u-toob

start with sandpaper and double sided tape in the drum, magic marker some lines on the shoes, put it together and scuff it a bit and you'll see how good the fit is
1 member likes this
by OriginalScott
I think the real answer is a different front brake. The larger conical front brake is a bit stronger but it still isn't great. The real benefit is that it fits right in the forks you already have. I have the larger brake on my B50 with extended arms and original shoes. It works but it isn't as good as my T140 with a single disk.

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1 member likes this
by OriginalScott
That brake came standard on the 1971-72 B50SS. It was also used on the 1971-72 Triumph 650 twins and 750 triples as well as the 1971-72 BSA 650 twins and 750 triples. It will bolt right up to your forks with no modifications. It isn't recognized as a great brake though. I would call it adequate on a 300 lb B50 and dangerous on a 400+ lb triple. Here it is on my B50 mashup.

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1 member likes this
by johnu
Thanks Scott, that's a beautiful bike:)
1 member likes this
by Tridentman
Just out of interest the front conical brake is also a straight swap for the 6" SLS front brake originally fitted to the 1973/74 Triumph Trophy Trail.
This is because the fork lowers are identical to those on the BSA B50.
The conical front brake is not a great brake IMHO-- however if set up properly it can be adequate on a 500, barely adequate on a 650 and totally inadequate on a triple.
People say that set up so and so it is a good brake.
That may be the case but the problem on a relatively fast and heavy bike like a Trident is brake fade.
A few hard stops through twisty road sections and the front brake lever seems to get closer and closer to the grip.
Definitely not confidence inspiring!
1 member likes this
by BSA_WM20
When properly adjusted , which this one is not, they will lock the front wheel of an A65L doing 80 mph in a 30 zone even when fully laden with 50 Kg of camping gear approaching a police car .
George Heggie had no problems with them on his A75 that he raced both in the day in production class & latter on in Historic racing .
1 member likes this
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