MrMook
MrMook Reader
12/5/21 9:12 p.m.

I have an 88 S15/S10 with awful stock brakes. Single piston fronts, drums in the back. I definitely plan to upgrade to dual piston brakes from a 98 Blazer for the front. Wondering if it's worth my time/money to add discs to the rear as well, especially given the lack of weight in the back, and no ABS. 

Planning a non-competitive build. Tuning up the Iron Duke, fixing broken stuff, lowering it a bit, and making it stop as well as possible.

No Time
No Time SuperDork
12/5/21 9:16 p.m.

I think the biggest benefit you'll see if you install rear disks is that the rear brakes will never be out of adjustment. 

GM drums on the trucks never seem to self adjust consistently (or in some cases ever), so you can take up on the adjusters and have great braking for a while, but eventually they wear enough to be out of adjustment and become ineffective. 

irish44j (Forum Supporter)
irish44j (Forum Supporter) MegaDork
12/5/21 9:18 p.m.

My 89 Raider has the stock front discs and rear drums. Drum brakes are perfectly fine as long as they are setup and adjusted correctly, especially on a non-performance vehicle (unless it's some kind of crazy track S10). I can lock up my rears even with 32" all-terrains on it if I try. 

Streetwiseguy
Streetwiseguy MegaDork
12/5/21 10:01 p.m.
No Time said:

I think the biggest benefit you'll see if you install rear disks is that the rear brakes will never be out of adjustment. 

Until the caliper slide pins seize solid and the caliper has to bend to apply the brake.

If it's got the 9 1/2 inch brakes that first showed up in every GM in the 70's, they will work well if clean, lubed and assembled correctly.  I have an adjustable prop valve in my Camaro that made a huge difference in balance. 

The later ones designed to compensate for abs suck donkey balls in most ways.

wvumtnbkr
wvumtnbkr PowerDork
12/5/21 10:23 p.m.

We Raced a old Malibu g body in endurance road racing.

 

Never upgraded the rear drums.  Just purchased good shoes (there are racing shoes for gm drums).

 

Loved them.  Never had any issues.

 

In other words, upgrade the front (if needed) and leave the rear alone, but freshen them up.

 

I'm also not convinced the front needs much other than maybe a good pad compound.  Single piston isn't the end of the world.  Even rx8s (which have pretty good brakes) had single piston.  Same with BMW e30.

irish44j (Forum Supporter)
irish44j (Forum Supporter) MegaDork
12/5/21 10:58 p.m.
wvumtnbkr said:

We Raced a old Malibu g body in endurance road racing.

 

Never upgraded the rear drums.  Just purchased good shoes (there are racing shoes for gm drums).

 

Loved them.  Never had any issues.

 

In other words, upgrade the front (if needed) and leave the rear alone, but freshen them up.

 

I'm also not convinced the front needs much other than maybe a good pad compound.  Single piston isn't the end of the world.  Even rx8s (which have pretty good brakes) had single piston.  Same with BMW e30.

And early e30 318s also had SOLID rotors in the front and drums in the back and seem to stop fine. 

I'm going to (respectfully) disagree with the group here.  While single piston fronts and drum rears were common in the 80s and 90s, technology has evolved and so have brakes.

If it were my own S10, I would absolutely do the 2-piston front swap and disc rears.  I suspect you can do the project very inexpensively and easily.

I'm a fan of any modification that makes a vehicle safer, and I can't see a way that your upgrades will do anything other than improve upon what you currently have.

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) SuperDork
12/6/21 1:13 a.m.

In reply to Loweguy5 (I'm not that fat, I'm big-boned) :

I kind of agree with Loweguy.  If you are keeping the truck long term switching to discs also makes for easier maintenance.  The main issue will be the rear parking brake mods.  

DrBoost
DrBoost MegaDork
12/6/21 2:25 a.m.

Drum brakes, when set up properly, actually provide more stopping power. I wish I had the article to prove it. But think about two things. Swept area and leverage. 
swept area, or total braking surface is MUCH higher in a drum setup. 
leverage. 100% of the braking surface is as far from the center of rotation as possible, maximizing leverage. In a disc setup next to none of the braking surface is at the outer edge of the braking circle. 
the areas where discs shine over drums, you won't benefit. They are much more resistant to fade, and water is shed from the braking surface. 
there are other advantages, but those are  the main braking advantages right there. 
some of this might not be clear. It's 2:30 am and I'm suffering through a gallbladder attack. I'm doing my best. 

autocomman
autocomman Reader
12/6/21 2:50 a.m.

I feel like I have to throw my two cents in here I'm not sure why. Here's a good example, I have a 2019 Buick regal TourX, it's my daily driver. Overseas you can get this car in a GS trim package which had big front brakes. The stopping distance between my car and the one with the big brakes I think is within feet. It's really no difference when it comes down to it.  Once the wheels lock/abs kicks in the brakes can do no more.  Were you benefit from the big brakes is heat dissipation. Yes I am simplifying this greatly, but if you can threshold brake over and over again you can put most cars into a situation where the brakes would fade and stop working. The bigger the brakes, the more you can do this without that happening.  Larger tires too can decrease the change of the wheel locking under braking, so bugger brakes could be taken advantage of as the threshold for locking would be higher.  So if the OP can lock up all four wheels with the stock brakes, The question begs to ask, do the brakes really need to be bigger?  And if he can't, what is wrong with the stock brakes?

Now there are obvious reasons for an upgrade, the ones I mentioned being able to get on the brakes longer get them hotter, more stops from high speeds with less worry about fade. Possibly rebalancing the brakes putting more of the bias towards the front, because of the tendency for the rear to lock up with no weight can have added benefit. However with more the work being done by the front brakes if you rebias then, it then begs the question should you probably upgrade the front brakes? 

From experience I have driven cars with horrible brakes, that shouldn't have horrible brakes. In the end it ends up being a poor quality of brake pad and rotor. Yes rotors alone can cause a brake system to work very poorly, I've experienced this on more than one occasion, once on my own car.  My suggestion would be to properly stage zero the brake system on that truck. It's an iron duke truck, 90 horsepower on a good day when it was new so won't be breaking any speed records. Refresh the front pads and rotors, and the rear drums and shoes with a known good quality parts. Personally I've used centric on most drivers  with no issues pads and rotors. They're very inexpensive, they're made by stop tech and they just work. You can also go with AC Delco dura stop stuff too.  But be sure you do it properly, new wheel cylinders, new spring kit, if the calipers are super old it's not going to hurt to swap them out they're usually dirt cheap. The brake pedal on that car should be firm and it should stop well without any question is too is it actually going to stop. If the pedal is mushy and the brakes just don't feel great, there's a good chance you have a proportioning issue or a brake booster issue. I have seen brake boosters lately cause all kinds of very strange pedal problems that you would normally start poking at the hydraulic system to try and fix.  Also very poor quality rotors can cause a brake pedal to feel strange as you're not getting the grip from the brakes with a normal pedal pressure so you have to push deeper into the pedal which can also feel strange. It's kind of a messed up cycle of crappiness.

As far as upgrading the front brakes to a two-piston caliper, I mean it can't hurt, but I don't see it increasing braking performance unless you have a larger tire and you can get on the brakes a lot harder before they lock. Then you might benefit from a two-piston caliper. But if the rotor is the same size, eh. For stock daily driver, a good stock brake setup should be fine.  But if you're going to be changing the calipers anyway, and it'll be swapping all these parts out, pads rotors calipers, you have nothing to lose and it may not be a bad idea to upgrade if the price is comparable.  

But to answer the OP question about doing disc in the rear, on a stock vehicle like that I go not so much. The advantages you won't have to adjust the rears anymore, the disadvantages you have to figure out how the parking brake is going to work. You can grab everything from one truck and bolt it on and your stock parking brake cables work great, then you get otherwise figure out how the parking brake cables will work. And in my experience, you can't beat a standard drum setup as a parking brake, versus the integral parking brake inside the rotor hat, or the parking brake calipers. I'm sure I'll get flack for that, yes they all work, but nothing holds as good as properly adjusted drum brake.  And no the self-adjusters never work, I've never seen one work, I've never heard of one actually working, so who knows. I've always had to go back in there and adjust everything manually every 3 to 6,000 mi depending on how and where said vehicle is driven.  I don't think we need to get into the discussion though of what it's better disc or drum.  Because in the end if you end up locking up the wheels it doesn't matter at that point. The whole point is better more linear control of the brakes before the wheels lock, and how do you achieve that without re-engineering the wheel

( see what I did there ;)

Cousin_Eddie (Forum Supporter)
Cousin_Eddie (Forum Supporter) Dork
12/6/21 6:21 a.m.

There was nothing wrong with the brakes on those S10 pickups. I was Mr Goodwrench back when they were new then I later spent 7 years fixing LLV mail trucks which had the same drivetrain. I have more experience than most with these things.

Start with a thorough refresh to original specs with good parts. Cut no corners. Don't forget the brake hoses too. After that you'll have plenty of brakes for any S10 pickup that retains the factory drivetrain.

People go on and on about ease of maintenance. That argument doesn't carry any water. A set of fresh rear drum brakes on an S10 will last a couple of hundred thousand miles as long as you don't drive around with the park brake on. You might pull the rear drums off every 5 years or so and make sure the self adjusters are still working freely. 

 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/6/21 6:58 a.m.

Drum brakes pack more braking power into the package at the expense of less linearity.  The self energizing effect makes them more prone to locking up, and also makes them more sensitive to being wet.  Disk brakes have no self energizing effect so they are a lot more linear with respect to braking force vs hydraulic force vs speed.

 

If you're not having problems with brake lockup, I'd leave them alone.  Those drums are waaaaaay more reliable than any rear disk setup, especially the setups GM used in that era.

Disk brakes also NEED hard work to stay in good shape.  One of GM's biggest truck mistakes was when they went to rear disks on the Silverado in the late 90s/early 00s.  Instantly went from having to address the rear brakes every 100k or so, or when the axle wore through at the bearing, causing the seal to leak gear oil all over everything, to replacing pads and rotors and sometimes calipers every 20k or so.  They don't get hot enough to completely burn off overnight flash rust, they don't wear fast enough to not seize up all the different sliding surfaces.  And that's on a fullsize pickup.

eastsideTim
eastsideTim PowerDork
12/6/21 9:26 a.m.

I'll mostly go with the majority that it isn't worth switching to disc brakes, except for one exception, that I myself met on my S10 project.  I found an 8.5"/8.6" 2WD rear axle under a Jimmy in a local junkyard.  It already had disc brakes, so no point in converting it back to drums.  But, no, I don't think I'd bother with converting the standard 7.5"/7.6" rear to discs.

Mr. Peabody
Mr. Peabody UltimaDork
12/6/21 10:49 a.m.

I drove S10's for a long time towing things I should not have been towing with an S10 and brakes were never a problem.

That aside, in a compact truck application like an S10 there's so little weight in the back what you already have is probably overkill. I'm of the opinion that for most applications a rear disc swap is aesthetic at best.

wspohn
wspohn SuperDork
12/6/21 12:03 p.m.

Some cars were manufactured with inadequate and/or undersized disc brakes, but the vast majority of complaints about braking are really due to poor maintenance and/or choice of pads.

In the old days, rear discs (two of my cars from the 50s had those) were good at stopping but quite poor in terms of an effective parking brake, which resulted in my choosing to opt for rear drums on my GM V6 powered MGA with Fiberfab body - I wanted to ensure effective parking brake operation.  Always nice to have confidence that your car will be where you parked it on a hill when you come back to it.

Today's rear parking brake provisions on discs are better - you'd have to check your particular vehicle to know where it falls.  I doubt that you'd see much gain by going to rear discs, though, as long as the drums are maintained and properly set up.

MrMook
MrMook Reader
12/6/21 1:33 p.m.

I knew this was the group to ask. Thank you all for your input. 

The truck has historically been a "death trap" especially in the rain. I was once looking at an old steam tractor in a museum, and the brakes were a block of wood that you pressed against a single cast iron drive wheel by pulling on a long lever as hard as you could. It reminded me of this truck. It was my grandfather's truck (bought new in 89), then my dad's, and now my brother and I have adopted it to carry on for a third generation. Brakes are first on the list. Now, the truck's poor performance history may be due to simple neglect, and not lack of engineering on GMs part. My dad was known to drive cars into the ground, and did the bare minimum for maintenance. Surprisingly, the truck is still kicking, and is largely rust free despite it's long life as a beater/fishing truck in a well-salted state. 

To keep this thing going for another generation, our modest plans are to fix the awful braking, tune up the engine, freshen up the steering and suspension, and lower it a bit (for no other reason than I think these look quite nice sitting closer to the ground...nothing wild). Lowering options for these typically begin with a Belltech kit, which uses drop spindles. Since I'm buying new spindles anyway, I thought maybe this is a good time to get 2WD Blazer spindles, and run the dual pistons in the front. What some of you are saying has me re-thinking that, since, with a proper refresh and updated pads/rotors, and fresh drums, I may get this thing stopping at least as well as stock. Then I could also keep the stock 14" wheels with the dog-dish centers, which I'd be happy with for now, though I do have other wheel dreams. I'll run the numbers and see what's cost effective, but if there's no performance drawback to the upgraded front brakes, I may do it just to future proof the front end in case we want to change the "low-and-slow" build into something more "tire-shreddy" down the line. Or maybe one day I decide I really need to haul some large rocks down off the mountain. You never really know, do you?

I'm convinced though, that no matter what I do up front, I'll just update/rebuild the drums in the rear for now. It will be a lot less to fuss about, and work just as well for our needs.

 

rslifkin
rslifkin UberDork
12/6/21 1:36 p.m.

In my mind, discs are worth it.  But that's partly because I have an absolute burning hatred of drum brakes, and beyond a parking brake drum, I basically refuse to work on them. 

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
12/6/21 2:31 p.m.
Pete. (l33t FS) said:

Drum brakes pack more braking power into the package at the expense of less linearity.  The self energizing effect makes them more prone to locking up, and also makes them more sensitive to being wet.  Disk brakes have no self energizing effect so they are a lot more linear with respect to braking force vs hydraulic force vs speed.

 

If you're not having problems with brake lockup, I'd leave them alone.  Those drums are waaaaaay more reliable than any rear disk setup, especially the setups GM used in that era.

Disk brakes also NEED hard work to stay in good shape.  One of GM's biggest truck mistakes was when they went to rear disks on the Silverado in the late 90s/early 00s.  Instantly went from having to address the rear brakes every 100k or so, or when the axle wore through at the bearing, causing the seal to leak gear oil all over everything, to replacing pads and rotors and sometimes calipers every 20k or so.  They don't get hot enough to completely burn off overnight flash rust, they don't wear fast enough to not seize up all the different sliding surfaces.  And that's on a fullsize pickup.

Came here to say this.  Sorry to disagree with you DrBoost, but you're just not correct on this one.  They do NOT provide more stopping power, they provide more brake torque, but on a very non-linear curve.  Discs take more pressure to provide the same braking, but that is about the end of the comparison.  The threshhold between braking and lockup on drums is far from linear.  A skidding tire isn't very good at braking.  If drums were better, every NASCAR cup car would be running them.

If you can only get to 60% brake torque before they lock up with drums, and 90% with discs, it doesn't matter how much "self-actuating" force they can provide.  Bottom line is that you're missing out on 30% of your braking.  Imagine zooming up to a turn and having to slow down with drums.  You can only have 60% of brake torque (in this example) before you're at threshhold.  Your choices are either locking up the tires or 60%.  Discs are far better at being brakes.  It's why every manufacturer switched to them and every race body prefers them (some require them).

The old saying of "can you lock up your tires?  Then you have enough braking" is complete BS.  It's worthless if you can't access MORE of the braking before threshhold.  Sometime in a deserted parking lot, try backing your adjuster wheel off the whole way on drums.  You'll get nothing... nothing... nothing, then WHAM... lockup.  Incredible braking torque, but terrible braking performance.

Having said that, on an S10 I wouldn't worry much about it unless you're looking to up the performance possibility.  If you plan on drag racing it, don't.  If you plan on driving it to Kroger's, don't.  If you plan on rallyX, AutoX, or HPDE, yes, do the swap.

Gearheadotaku (Forum Supporter)
Gearheadotaku (Forum Supporter) UltimaDork
12/7/21 12:30 p.m.

I've had several S-10s and the stock brakes are just fine if maintained properly with good parts.

My 91 Firebird has the same front brakes and did track days with good pads and ducting, no issues.

eastsideTim
eastsideTim PowerDork
12/7/21 1:23 p.m.

Thought of one more general reason to go with discs over drums, related to serviceability, not performance.  I know, generally disc brakes are easier to work on than drums, but it's not that huge of a difference, unless you are in the salt belt.  Neither is fun to deal with, but drums just seem to get way harder to replace when rusty.  Won't matter if this is a fair weather vehicle.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/7/21 1:30 p.m.

In reply to eastsideTim :

Drums are all over disks for maintenace, because they need less of it.  And it is way easier to pull the axles out to play with the diff if you don't have to mess with the brakes.

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