How much advantage in adding rear disk brakes?

AJ/FormS said
My car does not have rear discs. She is a streeter.
She has 235/60-14s up front and 295/50-15s out back.
She has the KH 4-piston calipers up front and 10X2 drums in the back.
I gutted my P-valve, and adjusted the rear "proportioning", by changing the w/c's to 7/8s, then to 15/16.
She stops real nice with the front-end only diving a little (1.03 bars and HD Munroes)
The whole car just digs, how I imagine throwing out a parachute would feel like.
But; I wear out rear shoes about two to three times more often than the fronts, which is by design, cuz I have plenty of shoes and only one spare set of new pads left.
But I also have an 11/1 360 with a 4-speed so, you-know, plenty of compression braking.

BTW; the rear self adjusters, in the factory system, should not be self adjusting under light braking. The P-valve is actually a hold-off valve, so it takes a good amount of pedal to get the rear shoes
moving, and even more to get a click of adjustment. I run NO Proportioning at all and have never had an issue, and I back up every time I back out of my carport, ending in a 90* turn. I never give the brakes a second thought.
IMO, warning; OPINION coming;
To you guys with adjuster issues;
I'd be willing to bet that you guys are running automatics, and probably "built" ones and IMO, probably need to idle your engines down so they don't bang into gear and/or pull so hard. And before you say that your big cam monster street engine won't idle any slower; if it's smaller than [email protected]; that's malarkey. My [email protected] PurpleCam would idle down to 550 still pulling itself in First gear with an A833 and 3.55s.
Some of you just insist on running mountains of timing, because you can get away with it. Well here is just one example of why not to. I mean why do you feel the need to run 18 to 25 degrees of more of IdleTiming, with a 2400 or more stall, hmmmmm? Do you think the springs might not be able to keep up, lol. I don't get it, and I don't tune that way. Furthermore;
Ma Mopar put a wavy-spring in the Hi-drum for a reason. And a spring on the L/R servo for another reason. But you know, your "built trans" guy, probably left the one on the build-table and probably never gave the other any thought.
Anyway, this ain't helping the OP, sorry for the sidebar.

Nope.

Manual transmission in my Duster, no converter at all. Drums were fully rebuilt and adjusting exactly as they should with nice new springs and the adjusters spinning nice and loose before I swapped them out for disks. Challenger was an auto but it had a basically stock 318 with a stock transmission and no crazy idle or anything like that. Drums fully rebuilt and adjusting as they should. Timing shouldn't change a thing unless it's altered your idle speed, and even that's a stretch. So your argument is we're riding the brakes too hard in reverse and adjusting more than is necessary? Except the brakes can't adjust unless there's space for them to do that. Otherwise you'd always have the rear brakes dragging, which should be really obvious for anyone.

Simply put, if you always turn the same way when you're in reverse, no matter what your engine or brakes are doing, you can bet your adjuster on the outside of that turn will click over first. Will the brakes always be unbalanced? Of course not, the other side should follow soon enough. But if you drive enough you will end up making a hard stop and find you locked up one rear drum because it wasn't balanced on the adjustment. Been there, done that. Adjusted the brakes after and guess what? One extra click needed on the "inside turn" wheel.

As far as brake wear, I have driven old Brit sports cars, old American trucks, new vehicles with ABS both trucks and cars, and old stuff with manual transmissions and 10:1 compression like my Duster where I use a lot of compression braking, all front disk/rear drum. I've never experienced anything more than about a 2:1 wear ratio for the front pads vs the rear shoes (2 sets of front pads for every one set of shoes). Hell I've gotten 3:1 on some of the trucks. If you're changing more shoes than pads, well man, that just goes against physics. By the CG you should be doing about 70% of the braking with the front brakes, even with the big rear tires. So, 30% with the rear. The math is easy, 70% is a little more than twice as much right? So 2 sets of pads for 1 set of shoes. Even 1:1 wouldn't be right, to have the rears doing as much as the fronts is *** backward. To have them doing 2 to 3 times as much? You're saying you do 70%+ of your braking with the rear brakes. Despite the physics that says 70% or more should be up front.