Brake Hoses
ADR 7 requires that automotive brake hoses be fully fatigue tested,
manufactured in a way that they cannot be taken apart and pressure
tested to 3000 PSI (20,000 KPA). Amongst other things, stainless braided
hoses swell less under pressure, particularly when hot, giving better
pedal feel, but the types which are assembled at home and not
pressure tested are not street legal.
Brake Piping
Most automotive brake piping is 3/16-inch O/D or ¼-inch O/D plated
steel seamless tube with doubles flares or ball flares (drill point seats).
Under no circumstances make automotive brake lines with singles
flares. Copper lines are unsuitable due to fatigue hardening. All
approved automotive brake fluid connections are based on positive
compression seals, flares, flat copper sealing washers and lately,
positive o-ring quick connect seals. No new car was ever produced
with a taper thread fitting (ie. needing sealing compound or Teflon
tape). Some aftermarket calipers are sold with taper thread
connections and their acceptability with ADR’s is therefore debatable.
Check every connection for brake fluid leaks before driving the car.
Proportioning Valves
A well-designed brake system should always lock the front first. If the
rear wheels lock, the car will spin around. The purpose of rear
proportioning valves is to ensure that line pressure cannot rise to the
point of rear lock up. Up to that point, front and rear line pressures are
usually the same. A proportioning valve is not a band-aid for a badly
balanced system.
Handy Hints Dos and Donts
1. Don’t mix up calipers, left to right, bleeders always go to the top to
get the air out (some older European and English cars were built to
be bled backwards, making it hard to do at home). Modern cars
always bleed air at the top.
2. When trouble shooting a soft pedal, clamp all hoses, taking the
clamps off one at a time until you find where the softness is coming
from. If you still have a problem with all lines clamped, then the
master cylinder is the cause. If the pedal goes hard, it is fine.
Sometimes the hose itself can be swelling.