Brake Drum Cracked.

Shadowman

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Getting ready for my next adventure I thought I'd give myself a sporting chance and get the brakes working better as they still were not so good after renewing all the shoes. I did the test of holding the drum on a wire from the centre and tap it with a hammer. If it rings like a bell it should be okay. One drum from the front and one from the rear did not ring true and sure enough I found both to be cracked. So that is three out of four drums replaced because of cracks. I have replaced them with new shadow drums.
 

Albervin

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Getting ready for my next adventure I thought I'd give myself a sporting chance and get the brakes working better as they still were not so good after renewing all the shoes. I did the test of holding the drum on a wire from the centre and tap it with a hammer. If it rings like a bell it should be okay. One drum from the front and one from the rear did not ring true and sure enough I found both to be cracked. So that is three out of four drums replaced because of cracks. I have replaced them with new shadow drums.
That is a 75% failure rate which is right up there with Trevor's statement. I would like to know whether there is a greater failure of rear or front drums & why that may be so. I thought that if there was an alignment problem with the front or rear suspension that could be a cause??
 

indianken

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Non-VOC Member
Fellows,

Seeing all of these dead drums, I'm even more happy with the front disc
brakes I installed on my Rapide.

(I can here the knives being sharpened now by the Origionalists )

Ken Smith


That is a 75% failure rate which is right up there with Trevor's statement. I would like to know whether there is a greater failure of rear or front drums & why that may be so. I thought that if there was an alignment problem with the front or rear suspension that could be a cause??
 

nkt267

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VOC Member
(I can here the knives being sharpened now by the Origionalists )
Put a disc on the rear,put the bike on it's rear stand and with engine running and in gear we can sharpen them on the disc.:rolleyes::D
 

Tom Gaynor

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Cracked drums

I replaced a rear nearside drum which had a piece come out of it. I was told it wasn't uncommon, and some Vincent drums weren't up to much being made from "plumber's cast iron". (I don't know if that is true.) It wasn't obvious why it broke, no impact damage, so I concluded it was a casting flaw and had always been there. It wasn't a fatigue crack - I know what those look like - but it was a bit disconcerting to see that the piece, like a section from a pie-crust about 2" per side was fully rusted and had evidently been held in place largely by paint.
 

Vincent Brake

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Cast drums crack

Hi Guys, they are cracking as you bolt them on the hub.
1s there is the unevenness in bolting torking them down.
2nd there is unevenness as you tighten it down to the spokes (where the 90deg bend is) and couse a great offsett force on them.
3rd surface on pressed steel spoke flange isnt flat but uneven.
4 its mostly ****y material (GG 25)

This all is also the case why hubs (cast ones) are cracking also

The srongest part is the steel soke flange as it gives way (mostly) without giving in

so take care and have them bolting down as they have contact under the bolting surfrace and not beside it, as it creates a bending force on the drums, cousing the crack.

Best regards

Vincent Speet Brake:)
 

VinParts

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Non-VOC Member
I found one of my original rear shadow drums cracked. God knows how long it had been like that. The crack however started on the braking surface and had grown towards the outer edge. I thought it was probably a casting fault - difficult to imagine what else it could have been.


Try 50 years of use Tom.
 

Len Matthews

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VOC Member
Another thought; be sure when fitting a new drum, be sure that clearance exists between drum and spokes. I've had some where the drum casting has to be machined to achieve this. Failure to observe this point means the drum does not bolt up flush with the spoke flange.
 

Robert Watson

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I have a drum in my garage at the moment (of totally unknown parentage!) that had been bolted up to a hub, (I would say blindly but I know the perpatrator lurks amongst these lofty walls and I wouldn't want to cast a shadow on his fine reputation!) and brought to me to turn the new linings up to suit. There are I think about 9 substantial cracks in it. 6 of them run through the sprocket mounting holes and through the face of the drum, and others in the same manner except not at a sprocket bolt hole. We replaced it with another of unknown parentage, but one that rings a nice c#.

Wondering how fragile it might be I threw it on the concrete floor several times, and yet it remains in one piece. I know it can't be used as a dinner bell, so it off goes to cast iron heaven.

Robert
 
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