8 lug disc brakes

[mr.wrenches]

anybody know if there is a way to convert to 8 lug disc on my 70? I would hate lose my dana rear

[WorkinLonghorn]

Here are a couple recent threads;
http://67-72chevytrucks.com/vboard/s...d.php?t=344516
http://67-72chevytrucks.com/vboard/s...d.php?t=314193
Thought about it myself but with the drums operating correctly, I really don't see the need.

[mr.wrenches]

buddy you just made my day...thank you

[69GMCLonghorn]

I have to agree with WorkinLonghorn. I've really got no problem with drum brakes. I have 13" drums all the way around. I'm really easy on brakes, but even when I've stood on 'em at freeway speed, I don't think they've ever faded on me.

[Elephanthead]

A couple million 80,000 pound semi trucks can't be wrong. Unless you are constantly hard braking, drums are better. I don't see any reason to not do a switch though if your drums don't work and you want to do it.

[mr.wrenches]

i agree if the are working right they are fine but they suck in the rain..i like to drive my truck a lot just looking for a good easy upgrade

[70rs/ss]

Drums are OK, but any serious braking repeatedly (hauling a trailer, etc and you will enjoy the discs better). A pair of 8-lug disk brake spindles, rotors and calipers and you are up to today's braking standards 71-late 80's or early 90's are basically all the same, so go wrecking yard crawling!).

Trying to compare semi drums to passenger car/truck drums is kinda silly, by the way do you know how many semi's I've burn to the ground, because thier drums got so hot they ignited (AZ has lots of mountain grades) drums will fail and bad if over heated. If drums were all that why not still use them on the front?? Becasue disks are better, more modern, and safer.

[mr.wrenches]

good someone caught that i lived in AZ for 2 years there are some serious hills out there...and dam is it hot... so do i need just the spindles or the control arms as well

[70rs/ss]

The control arms are the same, so just the spindles, rotors and calipers. You may need to swap the balljoints, but I think the drum and disc 3/4 ton balljoints are all the same, if not the A-arms are for sure so just buy the balljoints for the disc set-up and you are ready to roll, grab the prop valve out of the 3/4 ton donor as well so your brakes work as they should.

[mr.wrenches]

cool buddy thanks

[WorkinLonghorn]

There's no question that for extremely heavy service the discs are better. I believe they recover from getting wet faster too.
You can get kits for the rears too,with parking brakes even.

http://www.blackbirdscustomtrucks.com/index.html

[Longhorn Man]

the big problem with the old 8 lug drum stuff is parts avalibility. They stoppped making drums 20 - 30 years ago.
However, I agree that on the 20 and 30 series trucks, the drums are plenty strong for daily driver duty.

And as far as the big trucks go... they are putting disc brakes on larger and larger trucks now. Peterbuilt garbage trucks have had discs for a while now.

[WorkinLonghorn]

LHM , They have them (8-lug 12" drums) at Auto Zone for $67, I bought two on Wednesday. Made in China, without the two large screw holes that the orig. had on my Dana rear.
Car Quest had them too,but over 100 ea. Now maybe that's different from the Eaton? Mine are 12x 2 1/2".
TruckStop shows an 8-lug drum 67-70 rear only. WLH

[Longhorn Man]

Yeah, I shoulda said eaton.
there's 2 part numbers on the dana drums, I think one has shoes 1/2 inch wider than the other. I have a list of dana brake part numbers somewhere.

[LONGHAIR]

Originally Posted by 70rs/ss

drums will fail and bad if over heated. If drums were all that why not still use them on the front?? Becasue disks are better, more modern, and safer.

First of all...so will discs. Yes, it takes more to over heat them, but that statement makes it seem like they are "perfect" and that is simply not true.

As for not using them on the front? It is purely about maintenance....or actually lack there of...
Back in the day, a car was a "machine" and was cared for as such. Today's average driver just gets in and goes w/o a thought. Everything is taken for granted...it is expected to perform flawlessly w/no effort or input from the driver.
To stop well (especially straight) drum brakes need to be adjusted to pull equally. It is not as critical in the back, or you would have seen that as standard equipment a lot earlier.

More modern? ...ok

Safer?....debatable. They are less likely to fade, they clean faster in off-road conditions, and they require less maintanence.

Better?....IMHO no. Power assist was put into common use because of disk brakes. They are NOT as efficient as drums in terms of effort required to make them function. Drum brakes are "self energizing" meaning that they work kind of like a wedge. As you apply pressure to the shoe an it contacts the drum, the top surface is somewhat "drawn in" to the movement. This increases the braking effect with less pedal pressure. Disks do not have this effect.
Like Elephanthead said, all of those heavy trucks can't be wrong. Yes, a lot of them have gone to discs on the front, but they still have the drums out back.

I gather from the original post, that you are referring to disc in the rear? Unless you are a big off-roading fan, messing in a lot of water/mud, you are not going to get better stopping. It is an expensive swap for no gain, other than looks.

[mr.wrenches]

Second edit on the same subject.
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[rcrahn]

Originally Posted by mr.wrenches

anybody know if there is a way to convert to 8 lug disc on my 70? I would hate lose my dana rear

Check out this thread on what I had done with my 14 bolt rear end. The swap to rear disks reduced the unsprung weight (of the drums) by 53 lbs. It is also a much cleaner looking set-up. Total parts cost was ~$300.
http://67-72chevytrucks.com/vboard/s...=252364&page=7

[justcuz]

Lets talk about brake drum availability. Got an Eaton? Where you buy new drums? If you find them how much? Now the disc brake conversion on the rear is more cost effective than replacing the drums. Caliper brackets for a 14 bolt work on Eatons, as do the 4x4 front rotors from a 44 or 10 bolt and you can use Cadillac calipers if you want/need a parking brake.

If you have an Eaton, with a 14 bolt Detroit Locker and axles, it only makes sense to upgrade it and keep it. A lot of people don't care for the Eaton, if not I'll take every one you want to get rid of. They are almost as strong as a 14 bolt, lighter, and have a smaller housing.

An HO52 by the way has the same 5200 lb weight rating as a 14 bolt semi-float. A 14 bolt full floater is rated at 6242 lbs and is right between the HO52 and the HO72.

[WorkinLonghorn]

Lets talk about brake drum availability. Got an Eaton? Where you buy new drums? If you find them how much?

The only on-line place I looked was TruckShop and as I mentioned above they have the rears.$109 (but my cataloque is 2006).Doesn't say "Dana or anything just 67-70 8-lug rear.

[justcuz]

Even if they were the right ones, thats $218 for 2 drums plus tax and shipping.
I can buy brackets from DIY for $69, rotors for $70 and the calipers in the wrecking yard for 15 to 20 bucks. Hardware and brake lines for another 30 to 50 bucks. So including wheel cylinders for the Eaton, brake shoes, and hardware it's cheaper to convert to discs and be able to by brake parts over the counter in any town with a population of over 5000 people.

Drums are OK for stock applications if you are staying close to home. Get out on the road, like my last trip to Wyoming, and see if you can buy brake parts for your old truck in Rawlins or Casper.

[capev86]

Discs recover faster than drums and you get more power from clamping on a disc than pushing on a drum......however, drum shoes have more surface area than disc pads and work great as an ebrake. i don't care for any rear disc brake kit that has the e-brake built into the caliper because you have a smaller surface area to lock the wheel, the mechanism can seize up in the caliper and you have an extra thing to worry about when swapping pads....the setup is just plain stupid. the best setup is 4 wheel disc with drum ebrakes in the rear rotors....you get the best of both worlds.....high performance brakes combined with good e-brakes that last forever because they don't get used for stopping. the disc front/drum rear is the most efficient and economical setup for most vehicles because 70% of the braking comes from the front. rear disc will give you 10% more braking power (not necessarily shorter stops) and the extra efficiency is a good idea for towing where you see more demand on the rear of the vehicle and for the obvious bling factor. i may eventually try to adapt late model GM truck rear discs to the HO52 on the back of my 72 burb 3/4T 2wd. i want to keep it a true GM truck capable of heavy duty use and i feel the aftermarket kits utilizing a hodge podge of parts falls short of what GM r&d has accomplished.