Dare I say it..Brake problem!

pegibson · Jan 6, 2011

Just a query really.
On my 88" 1971,
I have upgraded my brakes to dual circuit, servo assisted, with 11" 109 front drums etc.
Being from a 109" they have 2 cylinders per wheel on the front.

When plumbing in the master cylinder on a standard 88" the port furthest from the servo is used.
I read somewhere on tinternet if you have 109" front brakes, you use the port closest to the servo, because of the twin cylinders on each wheel, they need the closest port for more pressure.
Is this true?
Thanks

johnny curt 1 · Jan 6, 2011

nope the servo is connected to a rod that goes right through the master cylinder to the pistons wich if memory serves me right theyre both the same capacity all the way through but i wouldnt use a master and servo from an 88" on that system id rather use one off a deffender 110 to guarrantee meself its gonna have a better matched capacity for the brake pots at the wheels

but im sure someone else on here will have other ideas on how best to set these systems up

pegibson · Jan 6, 2011

johnny curt 1 said:
nope the servo is connected to a rod that goes right through the master cylinder to the pistons wich if memory serves me right theyre both the same capacity all the way through but i wouldnt use a master and servo from an 88" on that system id rather use one off a deffender 110 to guarrantee meself its gonna have a better matched capacity for the brake pots at the wheels

but im sure someone else on here will have other ideas on how best to set these systems up

I have the servo and master cylinder from a series already, so would be nice to use it.
I see your point though

johnny curt 1 · Jan 6, 2011

pegibson said:
I have the servo and master cylinder from a series already, so would be nice to use it.
I see your point though

it could be done with a series master but if it were me id have to refurb all the seals in it before i even think of useing it

also if your gonna use a series cylinder on that system make sure you adjust all the wheel cylinders to the point you can turn the drum easily but can just about hear the shoes touching the drums like the odd scuf /scuff sound as you rotate it thats how yer know theyre set right

otherwise its gonna be a right cnut to bleed

nrgserv · Jan 7, 2011

dual master cylinders operate one port first then the second port. cant remeber which way round it is, but as the plunger is pressed fluid is pushed out of the primary port. as pressure builds, an internal spring is compressed allowing the plunger to then start pressurising the secondary port.
primary ports should go to the front wheels, secondary to the rear.
connecting other way round results in rear wheels locking up every time the brake is pressed.

also, if your upgrading to 109 cylinders, use the 109 or 110 master cylinder, as someone else has already pointed out, the 88 wont have the capacity to pressure an extra two wheel cylinders. you'll have constant problems trying to get a good peddle.

Bump · Jan 7, 2011

So to upgrade to 109" front brake drums what do you need to buy? Just new drums, pistons, pads? How much are you looking at for a pair?

pegibson · Jan 7, 2011

I got the complete assembly with swivels drums etc, for free, from a friend.
I just bought new, drums, shoes, cylinders etc from paddocks.
I cant remember the price now, but not dear at all.

Bump · Jan 7, 2011

pegibson said:
I got the complete assembly with swivels drums etc, for free, from a friend.
I just bought new, drums, shoes, cylinders etc from paddocks.
I cant remember the price now, but not dear at all.

got any more 'friends'

Will have to find a scrap one to borrow them off then

pegibson · Jan 7, 2011

No, no more friends. :violin:

clivees · Jan 9, 2011

dont forget to check witrh your insurance first as some of then take a dim view of none standard brake's

ciderman · Jan 9, 2011

if you are using brake components in a blue box, check them carefully; if you can afford better do so.

pegibson · Jan 9, 2011

I think i might have to cut some of my wing to allow for brake master cylinder!
Do the 109's have different wings to allow clearance?

steve2286w · Jan 9, 2011

The 109 MS bore is 1 inch the 88 is 7/8"
wouldnt have though it would make much difference which way round the pipes went as the bore is same diameter
a new one isent expensive, but you could always try it first,
ive a 84 88 diesel, with 11" front drums it has the brake failure valve fitted , the manual shows front port ms to front port BFV to front wheels

Dare I say it..Brake problem!

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