[Healeys] Dual Circuit Brakes

[Richard Ewald]

::: Sigh::: Is this thing on?
The change to dual circuit brakes took place with the 1968 model year.
Don't believe me?
Go look at the Moss catalog.
MGB tells the story
The listing are:
MGB Single line system 1962-1967
MGB Dual line non-servo system 1968-1974.5
Looking at the Triumph listings TR-4s are single systems, and TR-250s (1968)
are dual line systems
Moss doesn't have pictures of an Etype brake system So I had to dig out my
complete and official E type.
The series 1 had a totally dual circuit system with dual master cylinders.
This shows the Jags racing heritage, not Federal regulation.
The Series 1.5 and 2 had a dual circuit single master cylinder with a servo
system.  The hydraulic diagram clearly shows that one circuit feeds the
front brakes, the other the rears.
And Trust me Charlie, Volvo did it for 1968, but when they got rolling they
did dual circuits they really did dual circuits.  Two separate circuits in
each front caliper, and single circuit in each rear.  So one circuit had 1/2
of each front wheel, and one rear wheel.  Lose one circuit and you still had
braking in each front wheel and one rear wheel. Interesting front calipers
on these cars, two hydraulic lines and 3 bleed screws.
Speaking of which, dual circuits can be both fronts on one circuit, and
rears on the other (very common) or RF&LR / LF&RR (used on some ABS
systems), or some strange arrangement like Volvo (and SAAB) had with the
dual triangle systems.
A quick look at almost any old car parts catalog will show that I am
correct.
Rick

On Fri, Mar 25, 2011 at 6:54 PM, Charlie Baldwin <mgcharlie at comcast.net>wrote:

> I'm thinking that it must have happened for Jan.1, 1970.