9in drum brakes

Bewy said
72,
For some reason most of my post [ #12 ] did not get printed. So I will try again.
For the same line pressure, a drum brake Chrys car will stop quicker than a disk brake car.
That is because C [ & many other brands ] use duo-servo [ DS ]drum brakes. This action links the two brake shoes & causes a wedging action of the shoe against the drum. In effect, the braking force gets multiplied with DS brakes & provides deadly stopping action. A highly efficient system.
In contrast, a disc brake is nothing more than a G clamp & has no multiplying effect. It also loses some clamping force because of it's open end which spreads open.

A disk brake requires faaaaaaaaaaar more line pressure than a DS drum brake to be effective. That is why proportioning valves are used with disc/drum brakes, to reduce pressure to the rear drums which would otherwise lock up from the high pressure the disks get.

. Ill propose a few bits of information to this argument. To consider a cast iron caliper as an open ended C-clamp is a stretch. Iron don't bend, its too brittle. If a production caliper can pump itself apart, its trash and has no place on a car. Ill say the disc brake system has 8x multiplication built in. A 4 piston caliper has 4 (!) 1.63 bore pistons with a total piston area of 8.448 square inches. The MC bore is typically 1.125 (.992 in2) for a roughly 8:1 factor at the pedal. Disc brakes only need the very minimum of clearance so there is no wasted pedal travel and the pad backing plates dont deform under extreme load. 15/16 drum brake pistons (.694 in2 x2) is only >1.4in2 of piston area using the same pedal force. The multiplication factor is only ~1:1.4, then you have to factor in the brake shoe leverage and if the full brake shoe is contacting the drum....all in all the drum brakes will stop you but they suck when wet, suck when hot and generally suck over a disk option. My 4 9's on my 65 Barracuda were sub standard. the 10's on my "S" were much better but the 67 Disks I have now are even better. Disk brakes cool faster, offer less brake fade, are self cleaning, shed water faster, can shed their pad dust far easier than a semi closed drum, are always self adjusting, and are far easier to service. Only draw backs of front disks are more costly to build which is a non issue on today's classics. Rears require a seperate E brake drum.