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What am I doing wrong? Conical
#795049 01/07/20 2:35 am
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B50 race bike- 8" conical brake on the front.
Put a new tire on and cleaned and checked the brake, put it all back together and something's weird now. With the wheel stationary, I get lets say 1" of lever travel. Spin the wheel however and the lever pulls almost to the bar. Almost seems that when turning the shoes move to another position within the drum. What did I do wrong on reassembly?

Thanks

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Re: What am I doing wrong? Conical
Mike Baker #795066 01/07/20 11:27 am
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have you wound in the micram adjusters and backed off one click on each? i find these settle down and need re adjusting soon after assembly.


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Re: What am I doing wrong? Conical
Mike Baker #795158 01/08/20 11:21 am
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Yea, Gavin, done that. Going to take it off a third time and see what I can find.

Re: What am I doing wrong? Conical
Mike Baker #795174 01/08/20 4:21 pm
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Thats a weird one, I have had issues with the brake plate retaining nut when it comes loose, but not straight after a rebuild, let us know what you find.


71 Devimead, John Hill, John Holmes A65 750
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MZ TS 250
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Re: What am I doing wrong? Conical
Mike Baker #795188 01/08/20 7:56 pm
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Seems to me there is some issue with getting the springs on the shoes properly, like over or under. Maybe they are causing the shoes to tilt making proper adjustment difficult.

Here is a photo of one I disassembled. I assume it is correct.

[Linked Image from i.postimg.cc]

Tom

Last edited by koncretekid; 01/08/20 8:03 pm.

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Re: What am I doing wrong? Conical
Mike Baker #795199 01/08/20 9:05 pm
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I’m no expert and it’s been at least 10 + years since I looked at a conical brake, but do the springs have one coil longer than the other? If they do then I would be inclined to turn the spring around. It doesn’t seem right to me to have the coil of the spring resting under the shoe. Or do the springs rub on the webbing of the brake plate? If so can they be fitted on the other side of the shoes, thus being in the spacious section of the hub?? Just an un-educated thought.


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Re: What am I doing wrong? Conical
Mike Baker #795204 01/08/20 9:29 pm
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Factory manual says: abutment pads must not be omitted and the asymmetrical return springs must be fitted with the short portion adjacent to the adjuster screws (they spell asymmetrical with two s and one m).

Re: What am I doing wrong? Conical
Mike Baker #795225 01/09/20 11:04 am
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It appears that the one I pictured had the springs mounted opposite to what the factory manual says. As both ends of the spring are rubbing against the brake shoe, I can't see how the springs knows which end is under which end of the shoe. In any case, the orientation shown above works fine.

Is it possible that the orientation of the springs was originally used on automobile brakes which had a self-adjusting mechanism that rested on the coils?

Last edited by koncretekid; 01/09/20 12:12 pm.

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Re: What am I doing wrong? Conical
koncretekid #795229 01/09/20 12:51 pm
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Originally Posted by koncretekid
As both ends of the spring are rubbing against the brake shoe, I can't see how the springs knows which end is under which end of the shoe.


The brake pad has a leading and a training edge. With the short portion in the wrong location it's possible that the pad is hitting too early on the wrong edge?

Have you seen this: https://youtu.be/MuSBFFLop4w

Re: What am I doing wrong? Conical
Mike Baker #795230 01/09/20 12:54 pm
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Mike, check the brake drum diameter ...Pull the shoes from the backing plate and see how they fit inside the drum, the arc of the shoe and drum should match..And as mentioned, make sure the leading edge of the shoe is the correct position


79 T140D, 96 900M Ducati 81 Ducati Pantah 500 ..On a bike you can out run the demons..
Re: What am I doing wrong? Conical
MarcB #795245 01/09/20 6:19 pm
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Originally Posted by MarcB
Originally Posted by koncretekid
As both ends of the spring are rubbing against the brake shoe, I can't see how the springs knows which end is under which end of the shoe.


The brake pad has a leading and a training edge. With the short portion in the wrong location it's possible that the pad is hitting too early on the wrong edge?

Have you seen this: https://youtu.be/MuSBFFLop4w


The springs, not the shoes!


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Re: What am I doing wrong? Conical
koncretekid #795254 01/09/20 7:52 pm
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Right, but if the springs are reversed, then the shoes won't present the correct edge to the drum first. The springs *do know* which end is where.

Re: What am I doing wrong? Conical
Mike Baker #795264 01/09/20 10:03 pm
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from the manual "it should be noted that the assymetrical return springs must be fitted with the short portion adjacent to the adjuster screws."
The pic above has them the wrong way round and in the wrong holes . As others have said above, cant say ive had this bother, its usually obvious if miss assembled, stuff rubs and looks/feels wrong test operation will show before full assembly. The spring ends should be in the outer most holes and will only clear the pivot bosses if fitted the right way round, I see what the guy in the pic did, moved the end inwards to get clearance.

Last edited by gavin eisler; 01/09/20 10:11 pm.

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Re: What am I doing wrong? Conical
Mike Baker #795295 01/10/20 11:20 am
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40+ years of owning British bikes doesn't mean one should assume they don't need to consult the manual.
I installed the springs on the top of the shoes as opposed to the brake plate side because..... I've always done it that way.
No idea why it makes a difference, but it does. Anyway, thanks for all the responses.

Re: What am I doing wrong? Conical
Mike Baker #795298 01/10/20 12:21 pm
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Glad to hear you got them working properly.

from the manual "it should be noted that the assymetrical return springs must be fitted with the short portion adjacent to the adjuster screws."

Interesting that the above quote from the manual (I don't have the manual) does not mention putting the springs under the shoes. Does the manual say to put the springs under the shoes elsewhere?

Tom


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Re: What am I doing wrong? Conical
Mike Baker #795306 01/10/20 1:54 pm
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In the manual there is a clear picture showing the springs fitted beneath not on top. Quote was from the 1971 BSA manual, I doubt if Triumphs are different. I think they are fitted under in case of breakage.

Last edited by gavin eisler; 01/11/20 7:05 pm.

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Re: What am I doing wrong? Conical
gavin eisler #795328 01/10/20 7:05 pm
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Originally Posted by gavin eisler
In the manual there is a clear picture showing the springs fitted beneath not on top. Quote was from the 1971 BSA manual, I doubt if Triumphs are different.

The Triumph manual doesn't specify spring orientation in the text, but the pictures are clear.


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