Brake mods??

[Brooks James]

70dart manual front disc drum rear
Remember reading that the stock rear drums had a tendency to lock during hard braking. The cure was supposed to be get a 15/16 rear wheel cylinders as replacements for stock (I think it was from a 70 D100) and add a proportioning valve and adjust to 70/30 or so. I will eventually update to large bolt pattern so I need this as a safe quick fix. Your impressions please???

 

[72bluNblu]

Depends entirely on your car’s set up. In 100% stock form the rears tended to lock up first, yes. And in that case changing the wheel cylinders can help, there are 15/16” and 7/8” bore wheel cylinders.

But if you run a staggered tire set up with wider rear tires, things change. If you alter the ride height, things change. If you run different torsion bars and springs than stock, things change. If you’ve done anything to change the weight distribution, you guessed it, things change.

So what I’m saying is, you should probably check your car before you start throwing parts at it. And if you’re really concerned about it, just plumb in an adjustable prop valve, as that will allow you to dial it in.

 

[jos51700]

You do what you gotta do to make sure the fronts lock first.
Nothing else matters much beyond that. Do what you gotta do to make that happen. There is NO certain part that will make that happen. Those wheel cylinders might be enough or they might not. Depends on your tires, your front brakes, your master cylinder, your weight distribution, your skill as a driver, road conditions, your fiber intake, etc.

Drive it CAREFULLY on a smooth wet road and hit the brakes? Rears lock? Start adjusting your proportioning, change wheel cylinders, move battery to trunk, whatever.
Fronts lock first? You're probably fine.

When my dart was stock, I had an incident where I was passing a school bus on a foggy morning, because I'm brilliant like that.
Dude in oncoming traffic decided he needed turn on his headlights since he was driving a white car and he was even more brilliant than me. I mashed the brakes, and my Dart swapped ends and I slid backwards off the road.

It's a real problem. At a minimum, I'd splice in the prop valve and dial the rears back. Hell, take em off. They are just glorified parking brakes on most cars anyway. Save changing wheel cylinders until you've got the rest of the system built. Massive binders up front can make it a non issue.

 

[Brooks James]

It’s a completely stock slant 6 suspension and brakes. My plan is swap to big bolt pattern 4 wheel discs, front and rear sway bars, a 4 link, and at least a one inch torsion bars, aftermarket market lower and upper control arms etc. etc. So after reading the posts I will at least get a proportioning valve. I’m a commercial driver and have never so much as put a scratch on a commercial vehicle but there’s always some idiot out there that causes me to brake hard. Yeah...I know it’s eventually coming. LOL