Disc/Disc vs. Disc/drum ?

[Smokin72on20s]

is a Disc/Disc setup on a truck far superior to a Disc/Drum setup? (front/rear) what are the positives/negatives to having disc's in front and in rear? and what are the positives/negatives of having disc's in front and drums in the rear?

[Longhorn Man]

stopping power is increased with discs, that is a fact, however, it isn't by much. I installed rear discs on an 86 Civic Si and my 60 - 0 distance improved by a couple feet. Granted, civic verses truck is apples to oranges, but it is still fruit.
Disc brake pads tend to wear quicker. At work, when servicing vehicles, if it has less than 75K on the clock and has drums, we don't even look at the rears, if it has discs, normally they are gone by 30,000 miles.
IMO, and there well be many who argue with me, it is not worth the money. 70 - 80% of your braking is up front, use your money to upgrade the front, then give the rear a well detailed rebuild, and it'll be money well spent.

[cornutz]

I agree, go with better stuff up front and possibly add a big brake rebuild from ECE on the back...

[Longhorn Man]

WOAH! One hr, and not only have I not been flamed...but some one agrees with me!

I guess I can take off this flame retardant suit now huh?

[68LSS1]

Originally Posted by Longhorn Man

WOAH! One hr, and not only have I not been flamed...but some one agrees with me!

I guess I can take off this flame retardant suit now huh?

Almost. I will agree putting on disc brakes WILL NOT decease the stopping distance most of the time. I say most of the time because if a worn out, ill adjusted system is being replaced then yes, stopping distance will decrease. If you can stomp the brake and can lock them up now you aren't going to gain anything. What stops the vehicle is tires anyway. No matter how good your brakes are if your tires don't maintain traction (in this case loss due to braking, i.e. sliding) you are not stopping quickly. You want to stop better put wider and stiffer sidewalled tires on. And before I start getting flamed see my sig. I am running Baer brakes on the front which consist of 13" rotors and 2 piston PBR calipers, stock rear disc on the 8.8 (Explorer) and a Hydratech hydroboost. But I will have the tires to compliment those items. There are other reasons for running those items also. If you can get the parts cheap I'd do it. I just prefer disc though.

[Smokin72on20s]

how much do the rebuild kits run? what if i could get some disc breaks for $250?

[Longhorn Man]

I'd still pass myself.

[Smokin72on20s]

just checked ECE rebuild kits are $290. so it would be cheaper to go with the disc's, so why not? also, what do you mean by "upgrading" the front disc's? you mean like getting cross-drilled rotors?

[Longhorn Man]

crossed drilled...slotted (I'd get the slotted ones, cross drilled ones tend to crack) better pads, bigger rotors, better calipers...ect.
And anyone who would pay 300 bucks for rear brake rebuild (stock stuff) is a sucker.
You could go to NAPA and do it for 100 bucks.

[tom hand]

Rear disc are pretty much a waste of time on a pickup....unless you have it loaded...you could pretty much do without the rear brakes at all...unloaded the front brakes do 90% of the work

[Budweis]

Originally Posted by tom hand

Rear disc are pretty much a waste of time on a pickup....unless you have it loaded...you could pretty much do without the rear brakes at all...unloaded the front brakes do 90% of the work

how do you figure that? if you are using a proper proportioning valve or adjustable one those figures are wrong. im thinking 60/40 or 70/30 sounds a little better. i guess it depends on how you set it up and if you have a 90/10 proportioning setup i guess rear disc wouldnt help much. another advantage is disc tend to disapate heat faster.

[68LSS1]

He's figuring that because most of the weight on a truck is in the front. On a car with better weight distribution it is probably around 60/40. Don't know that I agree with his 90/10 statement though.

[Budweis]

basically when setting up a any proportioning valve the idea is to put as much on the back as you can making sure that the front brakes still lock first, as locking the backs first in a hard brake situation can get dangerous. ive done alot of research into proportioning valves and thats basically the low down of them. other things such as loaded and unloaded can factor in so you want a safe margin.

[Tx Firefighter]

68LSS1 is right. If you can lock up your brakes and slide the tires with your drum brakes, discs are not going to gain you anything. Face it, an unloaded truck with sliding back tires is going to stop just as fast as one with 30 inch Baer crossdrilled unobtainium rotors with intergalactic calipers and holy water for fluid, with sliding tires.

I mean, sliding tires is sliding tires, it don't matter what makes them slide.

On a pickup, wieight balance and tire traction are usually the limiting factor. The one concession to this is if the truck is heavily loaded and the rear end is much heavier. Then, discs may help, but only if the stock drums are being overpowered.

[toddtheodd]

The only reason I have considered converting my rear brakes to discs is to eliminate the need to adjust my brakes. For some reason my drums don't want to adjust when I do the braking while in reverse. I therefore have to remove the drums to adjust them. Discs never need adjustment like that.
Also, discs never have a problem getting wet.
Lastly it comes down to looks. Disc brakes look a whole lot better behind some rims than drum brakes. Especially if they are cross drilled and slotted.
Todd

[grayw0lf]

Personally, I still prefer my stock '70 drum/drum. I've replaced way too many warped rotors over the years.

[1969 GMC]

I am eventually going to go with 4 wheel discs...but from a 4x4er's point of view, the discs make the rearend a lot lighter, and also as mentioned above the fact that they still stop when wet, oh and we can't forget the bling factor.

If drums are more than enough, then why does the big 3 use factory discs on the rearends of all their bigger trucks?

[72c10step]

Originally Posted by 1969 GMC

If drums are more than enough, then why does the big 3 use factory discs on the rearends of all their bigger trucks?

FYI, I'm not sure about the HD's, but I know that Chevy/GMC 1/2 tons at least are going back to drums in the rear. They are going to have large drums that require a change to 17" rims to clear them, and they're using the money they saved going back to drums in the rear to upgrade the front discs. Overall, the setup is the same price or a little cheaper, and the stopping distance is decreased.

[neonlarry]

I guess I'll weigh in with a couple of comments here. One area where discs front or rear are superior is in the wet, also as mentioned they don't need adjusting, they are much easier to inspect and service and under heavy use they will not fade as easily. One thing not to do with discs is to use cross drilled rotors leave those to the ricer crowd(if you don't believe me look at what race teams like Porsche run) they will crack too easily. One disadvantage to putting them on our trucks(unless you use some models of ElDorado calipers) is no rear parking brake.

[toddtheodd]

I don't remember where I saw it, but there was a rear disc setup that had mini drums inside of the disc's rotor. The mini drum was the parking brake.
Todd

[Budweis]

i agree with brakes locked disc make no difference but if proportioning is changed it can give less nose dive under hard braking and make vehicle more controllable. also definitely bout being wet their better. i think overall disc are better its just a matter of how you use your vehicle and if its cost effective.

[neonlarry]

I have those on the Neon, its just finding some that would adapt to our axles easily.
I just went with the eldorado calipers much easier to setup.

[Mudder]

I have disks all around and love em. They are lots better imo than disk/drums. Easy to change and less trouble. And they stop better. I do not have aparking brake but it can be had.

[crustysarge]

I installed discs on the rear of my 77 Trans Am by taking the rear brakes from a 98 Trans Am LS1 car I bough that was wrecked. My rear drum set up was in very good condition before I decided to swap. After much cussing and testing and $$$ I am no better off than I was. I bought a 9" booster and master cylinder and the correct disc/disc prop valve for a 79 Trans Am that was stock rear discs and I installed a manual prop valve to boot. After all the work (I had to fab some brackets as it was not a kit) I am thinking about going back to my drums. Just my opinion but discs on the rear of the car made no difference other that my time and money and I think they are heavier.

Now with that said the cool factor is something else as I have Weld Pro Star XP 16" wheels and the discs stand out and I get a lot of inquiries about the 4th Gen Trans Am parts and how I made them work.

[LONGHAIR]

Personally I think that the main reason that the "big 3" made the change to dics in the first place was the maintainence factor. Discs are far more forgiving as far as adjustment. If your drums are not exactly evenly adjusted the vehicle will pull under braking. This was a great improvement for folks that were not really maintainence oriented and/or didn't want bother with it.
Keeping a vehicle properly maintained used to be a lot more involved than it is today. So many people just put gas in and drive.......

Not to say that there were never non-power discs produced, but there were relatively few......because the discs need some help. Drums are "self energizing" and discs are not. So the very idea that discs stop better needs some clarification.

As stated you are far better off with up-graded fronts (larger rotors, better calipers, etc) and better tires to make use of them. If you want to spend some time and money on the bling factor......that's cool too, just don't think that you are going to make huge gains and you won't be disapointed.

There may be some more advantage to the 4X4 crowd in the self-cleaning aspect. Mud and gunk don't build up inside like drums would.

I don't remember what year they started it, but GM used a load sensitive adjuster on the rear brakes as early as '87. It was an adjustabble prop valve mounted to the rear axle housing that had a lever reaching up to the frame crossmember. As weight was added to the bed, pushing it down, more rear brake was added.

Also I'm thinking that the 90-10 ratio is a little off. If you had 90% front braking your truck would spin around every time you hit the brakes in the rain.

That being said I think that an adjustable proportioning valve would be nearly manditory on anything where the brakes have been modified.
Now if you go the "Pro Street" (or similarly disproportionately larger rear tires) route, then an adjustable valve would be an even greater benefit.