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Cota 247 with creaky 'n spongy front brake: solved


iconic558
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Thought I'd post this here rather than Monty section as most t/s's run drums.

Bloody odd this. Front brake creaks when applied when stationary and the lever feels spongy. The drum lining isn't split which was my first thought. Stripped the brake down and still does it...bit of a strange one?

When moving the brake works ok but is still spongy.

Any ideas welcome no matter how bizzare;)

Edited by iconic558
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Good ideas guys....the linings do have holes which i assumed were dust relief ports....for want of a better phrase, but they could indeed be riveted linings which could explain a lot.

Wheel bearings seemed fine when checked earlier but good shout.

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My guess is something is flexing or moving under high load

As you have looked into cracked drum,cable failure, shoe lining delamination, wheel bearings.

that leaves;

cam bush wear,

Break shoe pivot peg might be flexing when loaded, the shoes may also be flexing,

Is the shoe carrier plate lined up with the drum? (check it matches the drum really well when assembled. Have the breaks on hard before and during tightening the axle), Place a finger across the plate and drum, when applying the break , feel if there is any movement  This would mean that the shoes are not parallel with the drum across the face

is the cable arm ok, not cracked, flexing, etc? (starting to look at extreme stuff now).

 

 

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Brake cam to cam followers galling

Brake shoe pivots galling

Cable end galling in brake arm

Cable end galling in lever

One shoe contacting the drum before the other shoe

Brake shoes being tilted due to worn/loose wheel bearings or angular axle misalignment

Worn camshaft to backing plate fit causing camshaft to tilt

What is really important is not that it makes a noise, but that whatever is making the noise may also be the source of the spongy feeling

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Well I've seen it all now. 

Stripped the shoes off the back plate and found a metal packing piece under each shoe on the brake cam....not sitting very well and not sitting flat.

Without the packing piece there was not enough adjustment left on the brake cable.

Just delivered the wheel and brake to Charles Johnson in Norwich to get the shoes religned with decent trials compatible material with minimal clearance....I think its a Ferodo greenish high metal content material..... 571?

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Yes shoes are available but far better to get the shoes 'matched' to the drums.

Also the off the peg shoes are usually road material that just happen to cross reference to to trials bikes. 

Edited by iconic558
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Picked the religned shoes today from Charles Johnson's...great service, usual turnaround is 3 days but I dropped them off yesterday afternoon and they were ready this morning as they knew I was needing the bike for a trial this Sunday. They as tight as on the drum too, not a lot of wiggle room. When I bought new shoes for my Speedy they had loads of slack from new.

Mark, the guy I dealt with is as keen as mustard too and a just really nice guy to deal with. He was very patient with my rookie questions on religning shoes.

Top Class serviceB)

Edited by iconic558
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