Barely any Brakes

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I understand the point about drums not being that bad. I have had several cars with drums all the way around and when properly maintained, they do stop your car.

But here is the problem........

Just about every other car on the road will have a shorter stopping distance than an old 4 wheel drum A-body.

And you can't control the other guy.

The cost of a disc conversion is about that of an intake and cam swap if you do a 73+ disc swap.
 
Just about every other car on the road will have a shorter stopping distance than an old 4 wheel drum A-body.
As a mechanical engineer, I fail to understand that point. The best you can do is apply the brakes to just before the tires skid (then coeff of friction goes down), and drum brakes can easily skid the tires. Of course nobody can do that, so the technique of "pumping the brakes" i.e. press until you skid, back off, press again. Anti-lock brakes do that faster than you could, but initial studies showed that they weren't effective in practice since the pulsing scared drivers who then lifted the pedal. You must train yourself to jam the pedal and hold it. Try a wet parking lot, and it does feel "wrong" when the anti-lock motor kicks in. Anyway, not all "modern cars" have anti-lock brakes. At least with my 1996 Voyager, it was an option (I have it).

There are a few other modern features in brakes. If a 67 or earlier A, you are advised to install a dual MC with separate front & rear tubing. Even better is the "X pattern" on the latest cars (left-front w/ right-rear, ...). But those only help mitigate failures and only if the warning lamps work, otherwise people can be driving around with half-brakes and not know it, which could be worse than a single pot where any failure is obvious.

For optimal braking, it is important that the brakes be balanced right to left. Indeed, they used to test that in FL vehicle inspections when I was young. One might make an argument that drum brakes are harder to balance since the "self-jamming" effect makes them touchier to variations in lining friction, but I haven't read that. It seems disks are more exposed to oil and road debris which could affect the pad friction. The main place where disks shine is that they cool off faster, which is important in multiple brakings from high speed, or "riding the brakes" on a long down-hill. The later is stupid, but the main reason disk brakes were mandated in 1973, to counter unskilled drivers.

I know that magazines give specs on braking distance for various cars. There are many variables in that, mostly in the tires used. I read a recent article where special snow tires gave half the braking distance on snow as All-Season tires. That is tremendous, and much more significant than the brake design. Slicks give much better traction on dry roads, but watch videos of road racers sliding off the road when it started raining, which is why they are outlawed for street driving. When you look at old figures for braking distances for Darts, keep in mind those were with narrow, bias-ply tires. I doubt there is much difference with "modern cars" today, if you use similar tires. Brakes have not changed much in 40 years. I have never run into anything in 38 years of driving, though many idiots have run into me (most had no insurance). I always maintain a safe distance. I have had enough "sudden stop" scares in freeway driving to know to stay back. If you run into someone, it is automatically your fault unless you can prove they changed lanes with no signal. Many studies have shown the main cause of accidents is idiot drivers, not poor vehicles. That is the reason most states no longer have vehicle safety inspections. If you want to see real idiots, watch the guys who speed on icy roads in 4 wheel drives, thinking they have special powers. Don't all cars have "4 wheel braking"?
 
Come on guys he is just trying to get what he has to work...........

Your drums will work when set up properly, will they stop fast no.
Make sure everything is set up correctly, small shoe int the front, springs proper tension, fresh wheel cylinders, clean lines.
Most important mic your drums, if any are too large, petal will be spongy.
 
I didn't want this to turn into a drum vs disc argument. I do have plans on upgrading to disc in the future, unfortunately I don't have that kind of money now.
 
So more important, where are you with this? Did you get things improved? Good pedal?
 
As a mechanical engineer, I fail to understand that point. The best you can do is apply the brakes to just before the tires skid (then coeff of friction goes down), and drum brakes can easily skid the tires.

The stock drum brakes will in no way, shape or form lock up the 275/40/17's I have on 17x9" rims all the way around on my Challenger. Not only can they not deal with that amount of traction, they can't deal with the added rotating mass.

The stock drums were ok for the stock tires, which were bias ply's. They're less ok for stock sized radials. But if you're going to run 14x5.5" rims and hockey puck hard BFG T/A's, they'll still do the job when adjusted properly, dry, and not overheated (notice the number of conditions there).

If you're upgrading to modern rubber though, you need to upgrade the brakes right along with it.

@plumkrazee70-

A '70 340 car should have had 10" drums from the factory, which is a good thing. Properly adjusted they'll do ok stopping a relatively stock sized tire/rim. I'd still plan on an upgrade, and I run 11 3/4" disks and 11" rear drums on everything I put on the street.

If you don't have a service manual, go here. No '70, but '71 was the same for brakes...

http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=service+manual
 
If you don't have a service manual, go here. No '70, but '71 was the same for brakes...

http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=service+manual

Unfortunately, many of the links on that thread are "broke."

Here's a refresh.

From MyMopar, several, including 66 and 70. But you have to "play" with page numbers, as they are not numbered to the original "dash" numbering

http://www.mymopar.com/index.php?pid=31

And from AbodyJoe, lot's 'o good stuff

70-71 Mopar Parts

[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/1970-71MoparParts.pdf[/ame]

72 Service Manual

[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf[/ame]

69 Dodge Serv. Manual

[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/69%20dodge%20service%20manual.pdf[/ame]

70 Dart Challenger manual

[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/70%20Dart%20Challenger%20Serv%20Man1.pdf[/ame]

71 Dodge Body Manual

[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/71DodgeBodyManual.pdf[/ame]

and this......................

65 Plymouth Manual

[ame]https://www.dropbox.com/s/upks33txhbe9tjw/1965%20Plymouth%20Service%20Manual.pdf[/ame]
 
So more important, where are you with this? Did you get things improved? Good pedal?

They have improved, but not to the point where I want to take it on the road. I drove it from my shop on the back of the property to the front driveway and washed it, then drove it back.

I got a new master and have decided to rebuild the drums. Currently pricing everything out.
 
Check the wheel cylinders too. I've seen them rusted solid, so they would never engage the shoes at all. Having this happen to one front wheel will cause you to spin during an attempted panic stop.
 
They have improved, but not to the point where I want to take it on the road. I drove it from my shop on the back of the property to the front driveway and washed it, then drove it back.

I got a new master and have decided to rebuild the drums. Currently pricing everything out.

Less common but possible, is a ballooning rubber brake line. The result of the line failing internally.

Being that you are looking at rebuilding the system, I would also replace the brake hoses, especially if they are of unknown age.

The pressure is going somewhere and without a leak that can only be a couple places.

It's bleeding back on itself (MC failure), expanding the wrong thing (ballooning a line), not expanding something enough (incorrect/worn parts and/or adjustment).

You could also have contaminated shoes.
 
Less common but possible, is a ballooning rubber brake line. The result of the line failing internally.

Being that you are looking at rebuilding the system, I would also replace the brake hoses, especially if they are of unknown age.

The pressure is going somewhere and without a leak that can only be a couple places.

It's bleeding back on itself (MC failure), expanding the wrong thing (ballooning a line), not expanding something enough (incorrect/worn parts and/or adjustment).

You could also have contaminated shoes.

I'm planning on replacing every thing: shoes springs adjusters, drums, hoses. Just have to find the best value/parts.
 
I'm planning on replacing every thing: shoes springs adjusters, drums, hoses. Just have to find the best value/parts.

Just FYI, if you're replacing everything, your cost will rapidly approach the cost where you could replace the fronts with disks. If you use a set of FMJ spindles from the local yard and Dr. Diffs ball joint sleeves, you could easily surpass the cost of the disk swap with a full rebuild of the drums.

As far as value, check out Rockauto.com. If they have what you need, you can usually get it pretty cheap. Especially if any of it is on clearance. The bad news there is that if its on clearance, they may not stock it again.

Parts for the 10" front brakes are not easy to find all the time, and finding replacement drums is getting very difficult for any of the 10" SBP drums. Before I started the rebuild, I'd make sure all the drums were in spec. If they're not, you may have an uphill battle...
 
Just FYI, if you're replacing everything, your cost will rapidly approach the cost where you could replace the fronts with disks. If you use a set of FMJ spindles from the local yard and Dr. Diffs ball joint sleeves, you could easily surpass the cost of the disk swap with a full rebuild of the drums.

As far as value, check out Rockauto.com. If they have what you need, you can usually get it pretty cheap. Especially if any of it is on clearance. The bad news there is that if its on clearance, they may not stock it again.

Parts for the 10" front brakes are not easy to find all the time, and finding replacement drums is getting very difficult for any of the 10" SBP drums. Before I started the rebuild, I'd make sure all the drums were in spec. If they're not, you may have an uphill battle...

I have added up what is needed to do the rebuild and I'm at $165 without the rear drums. I would like to do the Front disk brake swap, but our local yards are a joke for old Mopars.
 
Did you every mic the stock drums out?
Front drums are scary in the way people drive today. But they do work, just dont compare them to a modern car.
I have 9" stock drums all the way around 48 willys, everything new, at best all they will do is slow you down, panic stops turn into panic steer around...........
 
Just had to replace the rubber lines on front of my 70 Dart-collapsed internally-one side wouldn't flow any fluid to the wheel cylinder, and the other side wouldn't flow back to the MC and was keeping that set of shoes engaged.
Big fun trying to figure THAT one out!
 
As a mechanical engineer, I fail to understand that point. The best you can do is apply the brakes to just before the tires skid (then coeff of friction goes down), and drum brakes can easily skid the tires. Of course nobody can do that, so the technique of "pumping the brakes" i.e. press until you skid, back off, press again. Anti-lock brakes do that faster than you could, but initial studies showed that they weren't effective in practice since the pulsing scared drivers who then lifted the pedal. You must train yourself to jam the pedal and hold it. Try a wet parking lot, and it does feel "wrong" when the anti-lock motor kicks in. Anyway, not all "modern cars" have anti-lock brakes. At least with my 1996 Voyager, it was an option (I have it).

There are a few other modern features in brakes. If a 67 or earlier A, you are advised to install a dual MC with separate front & rear tubing. Even better is the "X pattern" on the latest cars (left-front w/ right-rear, ...). But those only help mitigate failures and only if the warning lamps work, otherwise people can be driving around with half-brakes and not know it, which could be worse than a single pot where any failure is obvious.

For optimal braking, it is important that the brakes be balanced right to left. Indeed, they used to test that in FL vehicle inspections when I was young. One might make an argument that drum brakes are harder to balance since the "self-jamming" effect makes them touchier to variations in lining friction, but I haven't read that. It seems disks are more exposed to oil and road debris which could affect the pad friction. The main place where disks shine is that they cool off faster, which is important in multiple brakings from high speed, or "riding the brakes" on a long down-hill. The later is stupid, but the main reason disk brakes were mandated in 1973, to counter unskilled drivers.

I know that magazines give specs on braking distance for various cars. There are many variables in that, mostly in the tires used. I read a recent article where special snow tires gave half the braking distance on snow as All-Season tires. That is tremendous, and much more significant than the brake design. Slicks give much better traction on dry roads, but watch videos of road racers sliding off the road when it started raining, which is why they are outlawed for street driving. When you look at old figures for braking distances for Darts, keep in mind those were with narrow, bias-ply tires. I doubt there is much difference with "modern cars" today, if you use similar tires. Brakes have not changed much in 40 years. I have never run into anything in 38 years of driving, though many idiots have run into me (most had no insurance). I always maintain a safe distance. I have had enough "sudden stop" scares in freeway driving to know to stay back. If you run into someone, it is automatically your fault unless you can prove they changed lanes with no signal. Many studies have shown the main cause of accidents is idiot drivers, not poor vehicles. That is the reason most states no longer have vehicle safety inspections. If you want to see real idiots, watch the guys who speed on icy roads in 4 wheel drives, thinking they have special powers. Don't all cars have "4 wheel braking"?
Thanks , so many old wives tales out there .
 
Did you every mic the stock drums out?
Front drums are scary in the way people drive today. But they do work, just dont compare them to a modern car.
I have 9" stock drums all the way around 48 willys, everything new, at best all they will do is slow you down, panic stops turn into panic steer around...........

I haven't taken it apart yet.
 
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