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11-inch brake modification

Les Henson

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As part of the modification to the braking system on catflap, I thought it a good idea to move the front wheel brake bleed nipples from the lower wheel cylinder to the top, where it's easier to access and also better placed to do what it's intended for.

You need to be able to make up lengths of brake pipe, or supply accurate patterns if you are going to get someone else to make them for you.

The standard arrangement is flexi-hose to an anchor point on top of the swivel housing, then rigid pipe to one of the two threaded holes in the upper wheel cylinder. A second rigid pipe then goes from the other threaded hole in the upper wheel cylinder - down the rear of the swivel housing to the lower wheel cylinder, and then the second threaded hole on the lower cylinder has the bleed nipple. As air bubbles in the braking system tend to rise, it makes sense to have the bleed nipple at a higher point.

In order to do this, the following pipe route has to be followed:-

Flexi hose to the bracket on the swivel housing as normal, then forward and down behind the brake backplate to one of the threaded holes in the lower wheel cylinder.

Another rigid pipe is attached to the second threaded hole on the lower wheel cylinder and comes up the back of the swivel housing to the rear threaded hole of the upper wheel cylinder.

The second hole is then free for the bleed nipple.

First pic is from above: 11-inch front and rear from a '76 109, Goodridge hoses, but same route as standard dual circuit system. Cupro-nickel pipes throughout the whole system, late series brake servo, and 90 master cylinder make up the entire sytem.

Pics are pretty self-explanatory.


The available gap underneath is ridiculously small. You need to take a lot of care not to put a kink in the pipe as you bend it, or leave the pipe so it rubs against the lower swivel pin.


The only hard thing about this job was those tiny bends in the pipe, at least a packet of brake pipe is only £6

Les. :)

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I've done this on mine, it doesn't make any difference to bleeding the brakes though, apart from accessibility.

The ports on the slave cylinders enter on the centre line, so air bubbles naturally rise above the ports! This means you still have to force the air out of the cylinders when bleeding and it doesn't make any difference whether or not you force the air through the top or bottom cylinder first.

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