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series 88" brake problem..


Badger90
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hi chaps..

my grandads series 2a has a brake problem.. there fine when going faward but then you back it up the the back brake come on.. it like the pads are catching the drum when going back.. have adujested them and not much happend..

what the problem?? anyone

cheers sam

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The shoes in drum brakes can be considered in 2 classes - leading shoes and trailing shoes. What happens is that as the drum rotates and the shoe is pushed in contact the leading shoe is pulled harder into contact with the drum by virtue of geometry and friction.

If you look at the back brake (so long as its still standard) the cylinder is at the top and the front shoe is the leading shoe (vehicle going forward) - with its leading edge at the top. Basically this shoe does most of the work going forward - but in reverse - things are reversed.

If you look further you will see that there are 2 springs - the bottom one connects the shoes to each other - and the light top one connects the front (leading) shoe to the backplate and pulls it off the drum and rests it on the adjuster. There is no spring or adjuster for the rear (trailing) shoe.

On assembly the ends of the linings should be bevelled (ie cut away at 45 degrees or more) so as to prevent the leading edges being 'grabbed' by the drum on application - this gives smoother braking and can eliminate 'grab' when the drums rust after standing overnight in damp conditions.

So whats all this mean - going backwards means that the rear shoe becomes the leading shoe - and if its edge is sharp it may be pulled onto the drum - bevelling it may well provide a cure. Also look for a sticky wheel cylinder piston - if its bad it may act as a ratchet - never releasing properly and maintaining some shoe pressure on the drum.

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who needs backwards anyway lol

my old 110 popped out of gear when going backwards, so i didnt use reverse

SORTED lol,

my only other suggestion has been said, with the chamfer on the edge of the pads.

mikey

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its had all new pads and cylinders all round.

i allso swaped the front drums to the back and vice verser in the hope that the front might be that little more worn and will cure it.. well it did for a short while and its started doing it again..

all that pads have that 45% angle on top and bottom.. i think its the pad at the back of the drum that is catching on the drum as the chap at the top said about the front and reverser thing.. i think his right that may be the problem..

so the top going from the pad thats facing towards the front of the truck.. theres a spring going from the pad to the mub that pulls the pad back.. a chap i spoke to did mention that if you pull that spring thats on the hub take it off there and clip it on the hole on the rear drum and that may cure the problem if not then where going to try a new set of pads differnt make this time... unless any of you guys have any ideas lol..

thanks for that chaps..

cheers sam

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If you are refering to the top pull off spring, removing it from the backplate post and fitting it to the trailing shoe, it will cure the auto application when reversing but it will also make you have no pedal so no brakes without pumping the pedal, as the trailing shoe will be fully retracted.

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