Brakes

If i were to get a brake pipe coil from Paddocks, what size would the pipe be?
Also, if i were to buy a new master cylinder, wheel cylinders and flexible pipes, would i need imperial or metric fittings? I'm planning to make a whole new brake system for my S3.

depends on age ie pre 1980 or later ,but imperial union look like this

metric like this

female end is metric,male imperial as it fits to cylinder

right, so i pretty much would need imperial fittings all round as it's a 1977

If your not keeping any of the original system the choice is yours.

I upgraded my 1978 swb series .
Changed from single to double pipe system.
Stuck with imperial . Copper/ nu pipe 3/16 I think. Can't be sure though long time back.
Put in a girling brake master and bearmach brake servo.
Also the tank for vacuum and butterfly valve assemble on air intake. Pdwa valve etc.
It worked about pretty expensive to do but great to have. (Once I get a chance to try it post restoration!)
Think I also put 11" drums etc. lwb on front and the 10" front cylinders on the rear.
Pipe fittings were brass 3/8x24 unf think. Obviously depended on cylinders used etc.

Okay, very helpful. Thanks.