disk swap on '74 or keep drums?

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rich006

rich006

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I'm relatively new to working on cars. I have a '74 Swinger with 4-wheel drums. I don't plan any high-performance driving, but I want a reliable and reasonably safe daily driver. As far as I know the drums and even the shoes are original (80K miles on the car) but I have recently replaced the 3 rubber hoses and the master cylinder. The car has always been garaged and is virtually rust-free with undercoating. Right now the car stops just fine, but there is a rubbing sound on each wheel revolution when driving (I think the noise comes from a rear wheel--it goes away when pedal or parking brake is applied). Based on my research I think I have 3 likely options.

1. Keep drum/drum and replace components (drums, shoes, wheel cylinders). Easiest and cheapest option, but doesn't give me disk performance.

2. Swap to '73+ disk brakes on the front. This isn't too complicated, but the problem is you get the 4.5" bolt pattern on the front. I'd need new front wheels and if I want the rear wheels to match I'd have to replace the rear end with the 8 1/4 rear that was on the '73+ disk brake cars. This seems really expensive.

3. Swap to Kelsey-Hayes disk brakes on the front. This keeps the 4" bolt pattern, so I can keep the same wheels and rear end. However, I'd have to swap out my '73+ upper control arm for the smaller '67-72 UCA (or is it '65-72?). This seems like a good choice depending on the cost. I just paid to have the upper ball joints replaced, so I wouldn't be too thrilled to have to swap them out.

4. Get an after-market disk swap kit with 4" bolt pattern. This is probably the easiest but not necessarily the cheapest or best option.

What do you all think? The existing drum brakes already provide enough stopping force to lock up the wheels if I really stomp on the pedal (I tried dry pavement at 30mph), so do I really need more stopping force?

Are the '73+ drum/drum systems adequate for modern driving if you don't plan to race? I get that the older systems are not so great, but are the later A-bodies OK with drum/drum?
 
If you are happy with the drum I vote for option #1 and rebuild what you have. Drums aren't bad, they just aren't the best looking, or easy to assemble/rebuild. They can work really well in a daily driver.
 
Drums can be ok, but in heavy "stop and go traffic" can heat up, then you loose your brakes. Also, if you brake quickly from a higher speed, they generate heat loosing stopping ability. If this type of driving doesn't apply to you, then you can rebuild your drums.
 
Nothing wrong with drum brakes. They probably stop better than discs.... ONCE.
Discs start shining when the brakes are applied repeatedly in a short amount of time or when the brakes get really wet. (don't ask). Lol.

The noise is probably the brakes dragging a little. It goes away when the brakes are applied because the shoes are rubbing the drum 360 degrees during the complete revolution instead of just one spot when not applied. Pretty normal noise if you feel no appreciable drag when turning by hand.
 
...Without a doubt convert to '74 up body discs.
Use the '76 and later callipers,they have 2 3/4 pistons instead of 2 5/8...and provide much more clamping pressure
 
A rear axle swap isn't hard. Also if you go with the A body 8.25 rear, you can convert the rear to disc brake very easily giving you 4 wheel disc brake. Just remember safety first and that disc trump drums anyday!
 
Drums have 2 disadvantages:
- They don't take as much heat before fading as discs.
- They will not work well if they get wet, like if you drive through deep water.

If you are not running in deep puddles or water, and not doing a lot of mountainous driving, then they will work OK. I have raced (rally) with disc front/drum rear combos and never had issues with adequately sized rear drums. And have overheated and faded disc/disc combos that were marginally small. So, discs do not always trump drums..... it all depends on how things are designed and implemented and the use to which they are put.

I don't plan to replace the drums at all my '62 Dart; it does not get driven or used hard at all, and they are generously sized.

You can get better shoe materials that will do better with fading on the shoes if you like; I used to get heavy duty (police duty) brake linings for racing from here:

http://brakematerialsandparts.webs.com/brakerelining.htm
 
there is no comparison at all.
2 3/4" caliper discs (73 74 'Cuda pin style or 76 up slider) in good repair with the correct master and hydraulic ratio will stop effortlessly with very little leg on an A body
 
I have the 1973 - 1976 Front HUB & DRUMS ++ BRAND NEW ++ in Original MOPAR boxes (nice keepsake box!!!) and N.O.S. ++ Asbestos Brake Shoes ++ to keep them gorgeous for our lifetime & beyond.... priced real RIGHT!!!!...just VERY heavy....
I am in Long Island, New York.... not too too far away.....
 
I have SBP, so the stock discs from 73+ would require new wheels. As I understand it, switching to the 8 1/4 rear would be the simplest way to swap the rears to LBP as well. However, installing a 8 1/4 rear (assuming I can find one) would involve shortening the drive shaft. It all adds up to a project that is really beyond my capability.

If I do the swap, I'm leaning toward the KH setup or an aftermarket SBP kit so that I don't have to mess with the rear end or buy new wheels.
 
4 piston A body Kelsey Hayes are a fine upgrade from drums.
..15/16" master cylinder is a good choice.
 
Well if you decide you want to go with a KH disk, Pm me. I'm gonna be taking a perfectly good set off my '67 Cuda, within the next couple weeks.I'll even have a set of small pattern ralleye wheels.
 
A lot of it has to do with driving habits and common sense. I had 9 inch drums on a valiant and never recall having fade in over 100,000 miles of driving. Poor brakes when wet, yeah, but if you drive slowly with slight pedal pressure, they dry pretty quickly. Back then, most people were staying under 70 on the freeway (OK, surface streets, too!), and I timed the lights and flowed with traffic, so rapid decelerations were rare.
I drove up and down Vail Pass in Colorado with those brakes, and had no fade problem. But I also didn't allow a problem to develop by doing 80 downhill.
Someone near Vail please chime in..............

When I return to daily driving in a Dart after my Mark 8, I will have to apply common sense, and start out carefully, as I am far more aggressive driving today. I will change to 10 in. drums just to keep up with the newer cars. Many more people are able to (better tires, suspensions), and do , drive more aggressively than in 1988.
 
I would do disc on the front. A '74 should have a 4 1/2 inch bolt pattern, though. How does yours have a 4"?
 
64physhy said:
I would do disc on the front. A '74 should have a 4 1/2 inch bolt pattern, though. How does yours have a 4"?
Click to expand...

Car with 4 wheel drums got the sbp. That said they also made a lbp 7.25 rear if disc were ordered and you got a slant 6 or 318 (318 could've also gotten the 8.25 if ordered).
 
The noise may be from not having used them much after sitting. Could be slight rust on the drum surfaces that will quickly wear off. Same thing when disk rotors sit. Indeed, rotors are more likely to drag or slightly touch.

I sure wouldn't recommend K-H disks on a 1974 since they are rare, espensive, and wouldn't even be original. For the same price, you could install Wilwood or SSBC, and for much cheaper Scarebird, though 1973+ disks might be smartest.

10" drums are fine IMHO. 9" drums are more marginal, more from the hubs using smaller wheel bearings (at least in my 1969 Dart). My 9" drums always stopped fine and could skid the tires (not fastest way to stop). The only time they over-heated was a long drive down a gravel road in the mountains on a hot day, when the car went too fast in 2nd gear so I had to keep using the brakes on the many turns (1st was too slow). By the time I got to the bottom, the pedal went to the floor (brake fluid boiled). On normal asphalt roads, just use the engine to control the downhill speed.

If your daily driving is accelerating to 60 mph, then braking hard at a red light every 1/4 mile, you could overheat drum brakes, but that would give abyssmal mileage as some fools don't seem to understand. Otherwise, they will work fine. The federal mandate for front disks ~1974 was to stop clueless drivers from riding the brakes down mountain roads and going over the side, aka FL drivers on the Blue Ridge Parkway. Not kidding. An in-law from FL was here a few years ago w/ a rental car and after driving 3000 ft up a mountain I asked if he knew how to downshift the transmission to take the heat on the way down and he had never heard of such a thing.
 
Thanks everyone for the perspective.

I confirmed the rub is in the left rear wheel, where the shoe was making contact with the drum every time around. There's quite a bit of brake dust there, considering it's only been 1500 miles or so since I cleaned and lubed the brakes, but otherwise everything looked fine. I backed off the adjuster a few notches, but it will probably retighten itself next time I drive. I guess the drum is slightly warped. Replacing both rear drums and shoes is easy and cheap, regardless of what I do with the front brakes.
 
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