Dang, you beat me to it.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

The biggest braking improvements to be made on our old cars are on the front. The front brakes simply do most of the braking. As the nose comes down in hard braking, the rear tends to rise, reducing rear grip.

If you have enough brake to lock all four tires repeatedly, you have enough brakes for those tires. Time to learn to modulate, and time to look for better tires!

There is room for brake improvement in the rear, it is just not as pronounced or cost-effective. The requirement for parking brakes complicates the issue as well.

Yeah, I want four-wheel disks. But it's low on the to-do list.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

OK, sure, I won't argue with any of that, but:

1) They cost a lot of money relative to real improvement achieved,
2) The weight savings is irrelevant on any but a race car, and
3) The rear-brake modulation problems on A-bodies can be solved with about $40 worth of new wheel cylinders.
Correct.

Yep, they drag. They also make parking brake setup kinda "involved".

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

True, unless you find a way to make it work for cheap.
Don't agree with that. Two ways to make a car faster, hp and weight. If weight can be saved (without durability issues), it should be. Plus, it's unsprung weight, which will make the car handle better, to boot. I know, cost is still an issue, but weight saving isn’t something reserved for racecars.
I don't think the problem is with the parts, drums are just inherently grabbier than disks. It's the nature of the beast since they are self energizing.
Agreed.

Still, if I can figure out a way to do it for a good price, I will. Again, to each his own.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

Well, what can I say? You're wrong! I'm not suggesting the rear modulation problem can be fixed with specific rear wheel cylinders, I'm telling you so. How do I know? 'Cause I've fixed a bunch of rear brake modulation issues by just that method. How'd I figure it out? By looking at the mods Chrysler made to the brake system of police-service vehicles starting in '62. They reduced the rear wheel cylinder bores to forestall rear lockup and improve rear brake modulation. So did I. It worked for Chrysler's cop customers. It worked for me, too. So...there you are.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

That takes guts, Dan. Nobody has ever told me I'm wrong before.

Ok, maybe one or two people have. Fine, lots of people have, but that only proves one thing, I've been wrong before.

But (you knew that was coming, didn't you ), I still say that it is just a band aid. Sure, Chrysler figured out how to make it work with the technology that was available, and for most people it's a good fix I'm sure. For the average non-car guy, it's probably not even really necessary. In the end, though, I think all you really did was reduce the effective force and made it less sensitive, but you've left some braking "on the table".

Have drum brakes worked for year? Sure has, and probably will for the next century. Is it the best setup? Not in my opinion. Are rear disks necessary? Not except is a very tight parameter. Do I still want them? You bet.

Is it worth the cost? Depends on the cost.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

Given the lack of really good options with really good brakes.....one drifts toward looking at what else there is.

I chose really good brakes as a way to balance the fact that narrowing an axle is not a really good option.

If I wasn t doing an Explorer swap I would probaly look to Ford 8".

If it isnt disc it should at least be 10" brakes....whatever the option.

I chose the 8.8 with disc because of its upgrade brakes and availability.

I bet where I live I can make those rear discs count and I have the tires to do it.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

I disagree (are you surprised?) with both of these statements.

1) You haven't reduced effective force. You've rebalanced the system so that less force is applied to the rear brakes (so they don't lock prematurely) and more force is applied to the fronts (which do a much greater chunk of the task of slowing the car down).

2) You haven't left some braking on the table, you've accessed braking power you couldn't access before. Think about it: If the rears lock when the line pressure is at, let us say, 270 psi, then the most brake you can apply without rear lockup and resultant loss of control is 269 psi, even though if it weren't for rear lockup you could apply greater force to the brakes and slow/stop quicker. If you rebalance the system such that the rears don't lock until, say, 315 psi, then you can apply 314 psi before rear lockup and resultant loss of control, which means you've got more braking available, not less. And if you rebalance the system such that the fronts and rears both lock almost simultaneously at 424 psi, then you're getting the maximum possible braking force from all four brakes, and you've certainly got more braking available than you did when the rears were locking at 270 or 315 psi. (these are totally random number used only for illustration of the point).

Taking this further, in fact, I would argue that it's much easier to leave some braking on the table/unavailable if you have rear discs, 'cause they won't reveal pressure application imbalance/mismatch nearly as clearly as rear drums will, so you can have a setup that doesn't lock up in the back prematurely but still is very far from the optimal front/rear pressure balance.

Rear discs are not necessarily better, motor-trade babble notwithstanding. Their rise in popularity is due more to cost and "market factors" (ignorant demand for them) than due to technical superiority.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

IF you have good front disk brakes, AND you fine-tune the rear brakes (say by reducing the wheel cylinder size) in order to just stop them from prematurely locking up, then YOU HAVE NOT "left any braking on the table." It defies physics. The only way to gain any more braking under those conditions is to add FRONT brakes, because ANY tiny bit of added rear brake will cause the rears to lock up and reduce the overall system effectiveness. And adding front brake will not let you add more rear brake either, because more effective front brakes simply increase weight transfer and take MORE weight off the rears making them MORE likely to lock. Now if you re-work the suspension to reduce weight transfer, that's another matter. That's true whether using drums or disks on the rear.


The only real gripe I have about converting our old cars to rear disks is that good factory-engineered conversions are few and far between- the Jeep to 8.25 conversion being about the only one I've heard of. Everything else is backyard engineered kit stuff that I'd really have to look over very carefully before I'd trust it with my life. Sure, some of it might be great, but even if it is initially good, who knows if there's not a bracket in there thats going to fatigue-fail after 20,000 miles? No thanks.

The other issue is rear parking brakes. And given the fact that the original REAR drums on MOST of these cars are more than adequate, I'd rather spend my money elsewhere- engine, front brakes, paint-and-body, suspension, etc. You name it, it probably will be a greater benefit than converting to rear disks.

Trucks- different story!!! Trucks can be loaded up so that the rears can do MOST of the work, and they certainly benefit from rear disks.

And EVERY drum-brake vehicle that will see use in anything more than parades and cruise night should be converted to front disks, IMO.

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If you are locking the rears because of traction, I would agree you are not leaving something on the table.

If the rears are locking because friction spikes and the brakes grab, you are leaving brake force on the table by reducing the wheel cylinder size. Not that you can do anything else with a drum brake rear.

My contention is, because drums are grabbier, you can't get as close to your traction threshold before lockup, while with disks you can apply (and use) more rear brake, if you have the traction.

I'm not saying this should be the second thing you do to a car, right after front disks. I am only saying that I believe there is a benefit, even if it is a small one. There are plenty of areas that should be address long before you get to the issue of rear disks.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

9 inch drums forever

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Repeating this will not make it true.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Why not? It worked with "Separation of Church and State" being in the Constitution.

It's ok, I can accept that we wont agree.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

Ditto...........

Don't forget the bias-ply tires

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Why not wooden wheels?

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car