That's the way they work on my 1982 Camaro, a lever operating a screw
through the piston. Earlier Corvettes actually had a small brake drum with
shoes in the center of the rear rotors. My 1974 Lotus has independant rear
suspension with inboard drum brakes, I heard they used drums because they
were having a hard time getting rear discs to meet emergency brake
requirements at the time.
Remember that drum brakes require less input because the turning force pulls
the shoes into the drum, causing some inherent boost. Discs don't, which is
why power brakes are more necessary with discs, and one reason why disc/drum
systems need proportioning valves to reduce pressure to the drums. That
self boosting property helps the drum type emergency brakes.
Regarding lockers and limited slips, with the clutch type Posi in my Camaro,
I can lift one tire, while in neutral with the emergency brake off, and
change the tire relying on nothing but the Posi clutches to keep it from
turning. In one instance I had parked on ground so uneven that one rear
tire was an inch off the ground (very stiff autocross suspension). The
other tire had no problem driving me away. These are relatively common
clutch type limited slips in American cars, typically identified by a metal
tag hanging off the axle that says something like "Posi-traction fluid only"
on it, because they require a posi additive to keep the clutches from
chattering. They do lose effectiveness as the clutches wear though. I've
had to replace the clutches in the limited slips in my Jeep and my Explorer
at around 100,000 miles. I put a Lock-Rite locker in my Bronco II. It was
a true ratcheting locker. It didn't lock unless their was significant
torque on the drive shaft, then it locked both rear axles together. It had
no differential spider gears, until it locked, it drove one rear wheel or
the other. Pretty squirrley on a short, light vehicle, but good off road.
You could lift one wheel and spin it with both the other tire and drive
shaft not turning. These are not common from the factory in American cars
or light duty trucks.
----- Original Message -----
From: "Jeff Shanab" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, August 11, 2007 9:46 AM
Subject: Re: [EVDL] Better Emergency BrakeRe: Better Emergency Brake
> Are there different types, this is my first car with disk brakes in
> back. The nissan 300zx caliper has a 1/4 turn jack screw through the
> piston. Same piston that the hydraulic works on.
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev >