Why did GM use brake drums for the emergency brake?

Certainly having cabled rotors for the emergency brakes would be fewer parts and less weight!

What am I missing :confused:

 

Must be for redundancy/separation of systems. If the calipers fail, the emergency mechanical system is still intact and isolated from the failed system.

Our "e-brake" is essentially just a parking brake anyway, and a lousy one at that. At 75mph, I doubt it would scrub very much speed off. :rolleyes:

 

Like Patches says, it's really just a parking brake. With modern dual zone brakes there's no need for much more.

I agree, however, it seems to add complexity over the more common parking brakes that just actuate the disc brake.

 

Actually they probably went away from the disk parking brake because of maintenance issues. The C4 had a non - drum parking brake from 88 through 96 and the GM mid size front wheel drive cars had something similar. Depending on how they were maintained the brakes had a tendency to freeze up and since the caliper was applying the pressure the brake fluid would boil and you would lose the rear brakes (I personally know some people this happened to, they did have a real moment when they hit the Interstate Off Ramp and found they had little braking). With the drum brake its less likely you will overheat the fluid in the caliper if the shoes freeze up so you are less likely to lose the rear brakes.
Bill

 

It was done to use the so called "self arrest effect" of the two shoes inside the drum. It´s the old "duplex system". When you take a look at the two (=duplex) brake shoes in the drum you see, that they are expanded on one side when you grab the lever. So driving forward or rearward, always one of the two shoes holds against it (sorry for my bad language) i.e.:
You drive a bicyle and hold a long wooden block in front of you to the ground. It will stop you easily faster than you like. Now try to imagine you hold that block to the rear and push it down, there will be a braking though, but no self arresting effect.
Whether you roll forwards or backwards with your vette, one of the two shoes is in self arresting position.
This self arrest effect is not on a disk brake. So the force to hold the car is much higher, the effect is not so good.

OK, the design of the vettes ebrake is very bad due to manually having to turn the star wheel and so on, but what I tried to exlain is the mechanical idea that is behind having drum as ebrake. Even better is this combined with a left foot pedal :D

Frederik

Correction: two shoes spreaded by one cylinder (or lever) are called simplex, if you have two cylinders for two shoes it´s called duplex. Sorry for this.
Frederik
[Modified by C5 Frederik, 2:41 PM 12/4/2002]


[Modified by C5 Frederik, 1:47 PM 12/5/2002]

 

Great explanation, Frederik! :cheers:

 

Yeah, except... There isn't two shoes, there is only one circular one.

I believe I read somewhere that the used the drum setup because it has an easier pull on the brake handle. Makes sense because of where they had to place the handle (very high and to the right, not where you could get a good pull on it).
Gary

 

It is ONE carrier ring, but on this ring there are TWO shoes or brake pads!

Tell me where do you see another possible place in the vette for the ebrake lever as where it is now? Nowhere IMO

Frederik

 

What emergency/parking brake are you talking about :confused: C5's don't have either. Seriously, even after adjusting the star inside mine still are worthless. Didn't want to adjust them to tight and end up frying my wheel bearings.