On Sat, 18 Oct 2008 18:46:59 -0500 (CDT), Robert Nichols wrote:
Larry Jaques wrote:
:On Fri, 17 Oct 2008 17:47:37 Jim Stewart scrawled the following:

:Most cars have two independent systems,
:right front/left rear and left front/right rear.
:
:Are you nuts, Jim? That would put a car in a spin in seconds flat if
ne reservoir were dry. I believe that all the cars I ever worked on
:up through the 90s had separate circuits for front and rear. I see no
:reason they'd change that. It's a real safety issue.
:
:If you know of crossed systems, please post a link. I gotta see this.

Seconded! Cites, please.

It's theoretically possible to make a cross-split, but also
technically difficult - you need either two residual valves for rear
drums, or four wheel discs that parking brakes are a nightmare on. Or
a parking brake system totally separate from the service brakes.

And theoretically very unstable on system half-failure - I'd rather
stomp on the pedal and get nothing than a guaranteed spin.

Without ABS, if you lost the front brakes you'd almost certainly lock up
the rear wheels in a desperate effort to stop with 70% of your braking
power lost, and that would be very likely to put you in a spin too.
That was the reasoning behind dual-diagonal split. My Saab had it back
in the 60's, and I believe the Fiat I owned back around that same time
did too.

Of course the Saab was so spin-prone anyway that a little extra didn't
matter much. A friend of mine once told me, "Everybody I've known who
owned a Saab has done a 180 in it." Yes, I'm in that category too, even
without a brake failure.

You SAAB owners must be cursed, or just not paying attention - I put
100K on a 61 Corvair that owns the "Tail-Happy Award" for the USA (The
Porsche 911 is a lock for Europe), and while I had it partly to mostly
sideways several times and caught it, I never once went all the way
around.

Most cars will give you a bit of advance warning that the stiction
is going away if you know to listen and feel for it.

-- Bruce --