9in drum brakes

Bewy said
Some common sense please. How many people are breaking 9" spindles? AJ has. Anybody else?
Breaking 9" [ or any other size spindle ] is uncommon. It is not a design fault. There would be other reason~~: spindle bent, fractured from previous collision damage, loose wh brgs, lack of lube to wh brgs or misadjusted, etc.~~

Bewy said
str12,
You get the gold star. 100% correct. I am seeing some nonsense in this thread from people who are usually more switched on.
There is a reason heavy vehicles use DRUM brakes.....

You missed it, I already posted the reasons why the drum brake spindles fail. Usually it's not the spindle, but the lower ball joint bolts that fail. The drum spindles used 1/2" bolts there. The KH disks used 9/16", and the later 73+ 10" drums and 73+ disk spindles used 5/8" bolts. The original drum spindle to lower ball joint bolts were undersized and corrected with later designs. The 9" spindles are also smaller in diameter and use a smaller outer bearing. The smaller outer bearing has less surface area, so, they're more likely to overheat and seize on the spindle, which hastens spindle failure as well. And yeah, if the spindle fails at the outer bearing the whole assembly goes away. The later spindles are thicker and use larger bearings so they're less likely to fail anyway, but if they did the rotor will still be captured by the caliper as already mentioned.

As for the "heavy vehicle" thing, there are more considerations than just braking performance. Semi tractors in the EU are mandated to have disk brakes. In the US most are still drums, BUT, that's because the drum brakes are cheaper to produce. The trucking industry lobbies the crap out of the government to keep the drums standard and not introduce a disk mandate (like was done for passenger vehicles in 1976!). And those are all air brake systems as well, which does change things a bit because the drums are a bit easier to set up to compensate for an air loss failure. And then there's the fact that most "heavy vehicles" are also limited to slower speeds.

Disks win every time when it comes to heat dissipation, remaining correctly adjusted at all times because it happens automatically and not with some clunky adjuster, and typically stopping distance but that is specific to the system if you assume the adjustment is correct at that given braking moment. Regardless, this isn't just an "disks vs drums" from a design or theory standpoint. This is the 9" mopar drums vs disk options for these cars, and 9" drums lose that all day long. Can you make a drum brake system that will outstop a particular disk brake system? Sure. But the 9" drums for these cars don't beat the disks available for these cars. Not even close. And that's what we're talking about.