The Altima post today made me think of this.When the road conditions are of the salty type drum seemed to be better.Im thinking of WI. and the small Blazers with 4-wheel disc,always alot of rust on the rears
i personally think disk are better, simply because they can be kept track of visually alot easier.
maybe for some who never look at them, drums may be better. but then again, i have not driven in to garage doors either!!
Rear drums could be better on vehicles without ABS, but in the end ABS with Four wheel disc is far better
One of the faults of a rear disk brake system where a ratcheting piston is activated by the parking brake to keep the rear brakes properly adjusted is, that those who own vehicles with automatic transmissions never use the parking brake. So the rear disk brakes are never adjusted properly. After a while, the piston can’t move out far enough to compensate for the pad wear and the caliper is just sitting there. Well! If you let a hunk of steel sit long enough in that environment guess what? It rusts!
The rear disc on the back of my old Taurus were Junk.
The lower pin that allows the caliper to float or move rusted inside the caliper mount and it always took PB Blast, heat and a vise grip to remove it. Even after a good cleaning, anti-sieze, sil-glyde, prayer, eye of newt, etc, etc it still locked up.
My 2000 Blazer was my first vehicle with 4 wheel disc brakes. Last year it failed inspection for the parking brake at ~80k miles. I took it to my trusted mechanic. The parking brake consists of a small drum brake built in the rotor on each side. The parking brake is not self adjusting, the calipers have to come off to do the job. He had to replace the parking brake pads and the disc brake pads also. After I got the truck back the calipers froze up and had to be replaced. About $400 later the truck passed inspection. The parking brake needs adjusting again, I think I’ll wait till next inspection.
My 95 Dakota pickup with rear drums, the rear pads had about 70% left when the front brakes were replaced at 70k. The rear brake were still in great shape when I traded it at 88k. This is why I like rear drum brakes better than disc. But the Blazer does have really good brakes when they’re needed. When my oldest gets her license in 2 years the brakes will get a workout no doubt.
What do you do with the parking brake? I have those same drum-rotor disk brake system in both my 2000 Ford Explorer and 1988 Toyota Supra. I’ve NEVER had to replace or adjust the parking brake system on either. Those parking brake shoes are thin from the factory, and not designed for rolling stops. I’ve replaced the rear pads numerous time on the Supra, and at least 3 times on the Explorer, and have checked the rear parking brake shoes every time. The Supra has 243,000 miles on it, and the Explorer has 167,000 miles. Plenty of meat, and no adjustment necessary.
I’ve also mentioned such a system with friends, and some of them also have them on their cars and trucks. They’ve never had problems or needed replacement, either. After dealing with the parking brake system as described by Tester above, I prefer to deal with this drum and rotor system. The rear disc brakes are free-floaters, like the front, and are easier to reset, since the pistons a single and smaller.
What can I say, it’s a Blazer, once all the moving parts are replaced it’s a fine vehicle. I use the parking brake normally, since I live in South Jersey, hills/inclines are not an issue. About a year after the new pads were installed, the parking brake was loose again. I never had a problem with the parking brake or had to replace the rear brakes on any other car I’ve owned. Generally I get about 70k out of my front pads, so I don’t think I’m too hard on the brakes as a rule.
When are rear drum type brakes better?
There are pros and cons to both systems. You asked about the applications where drums are better so here’s my double lincolns-
Cost. Drums typically cost less to manufacture and so contribute to a lower purchase cost. This does not take into account maintenance costs however.
Parking brake holding power. Drums are usually better in this regard and so are found on applications where vehicle weight or heavy loads might need to be considered.
Drum brakes provide more stopping power at a lower hydraulic pressure due to their leverage advantage. They can be superior for light stopping power with a shorter stroke volume like on light trailer surge brake systems.
Drum brakes are more protected from road dust and debris which can contribute to wear.
Drum brakes can be adjusted so they have little to no drag. Some drag racers prefer drum brakes for this reason.
Rear drum brakes are less expensive to maintain than disk brakes. This is because in disk brakes, the rotors can warp from excessive heat. I have never had brake drums warp, even when I drove a 1969 Dodge Dart with drum brakes on all the wheels. I have never had to replace a brake drum or get it resurfaced. All you have to do with brake drums is replace the pads. You can’t just replace brake pads with disk brakes. You have to get the disks resurfaced each time, making them thinner and prone to warp even easier.
If you’ve never had to machine a drum or had one simply wear out, then your sample size is too small. And the labor to do a drum setup is easily 2x that of any disc system regardless of the drum condition. Typically, labor is way more expensive than the parts. I can disassemble a caliper system, clean and grease the pins, install pads, slap on a new rotor and reinstall the caliper in 1/2 the time is takes to remove a drum, clean the assembly, pull the springs, shoe retainers, ebrake assy, install the shoes and misc hardware and then measure and adjust the clearance prior to reinstalling the drum. We won’t even talk about drums worn so bad the shoes are inside a wear ridge…
I was thinking of this from the perspective of a DIYer. You are right. It takes me a lot longer to change the shoes than it would a set of pads, especially when I need to go over to the other side to see where all the parts go. If I didn’t do my own brakes, it would probably be cheaper to get the rotors turned or replaced each time than deal with drum brakes.
If you change the shoes on time, how do you wear out a drum?
Disk brakes have a slight drag on the rotor, drum brakes are fully disengaged when not used hence the most effecient cars typically have drum brakes. Also, drum brakes don’t dirty up your wheels. Of course you can have great drum brakes and lousy undersized disk brakes so I can’t say that one stops better than the other. Personally, I hate doing drum brakes, springs that are a pain to put back in, drums that are stuck on, not fun on the otherhand, I’m not crazy to have to use a special tool to push the pistons back in on most cars with rear disk brakes.
When the auto maker wants to reduce product costs.
Self-servo drum brakes produce a great deal of braking with little effort but are more prone to locking under hard braking. Non self-servo drums are very simple but give little braking power, which is suitable to front wheel drive vehicles. The great stopping power and ease of adding a parking brake seems to be the reason that self-servo drums continue to be standard on some trucks but even there, discs are gaining ground.
Drum brakes on the rear seem to last a long time because they let the front discs do most of the work. I’ve had them last over 300k miles. I do not know why rear discs wear out so fast though.
There is always loss of material on both sides even with purely organic compounds. It’s just a matter of degree. An organic shoe will not wear the drum as fast as a semi-metallic pad will wear down a rotor but it still happens. In the “old days” you’d see a lot more inclusions in the friction material too so the drum surface would wear unevenly and develop ridges. Those should be machined out just like a rotor needs resurfacing (I prefer replacement) before new shoes/pads.
especially when I need to go over to the other side to see where all the parts go
Got a chuckle out of that because it is so true. I think anyone who has pulled both sides apart at the same time has only made that mistake once. I’ve ran into shoes that were so deep into the drum that I had to pull the whole works off with the drum quite a few times due to owner neglect. Air chisel off the shoe retainer heads and crank down on the puller. Sproing! Now try and figure out what went where to put it back together.
I’ll venture a couple of reasons; drum brakes should be adjusted so they are clear of the drum surface when not applied whereas disc pads tend to ride on the surface of the rotor more so they wear faster. Also, the rear brakes are subjected to all the dust and dirt kicked up by the front wheels. Those splash shields are only so effective at keeping dirt and water off the rotors/pads. It’s a balance between allowing convective cooling and sealing from debris.
Simple. Just look at the size of the rear disc and pad compared to the fronts, and then look at a comparable drum shoe surface on a rear drum brake system on a similar sized vehicle. The rear disc rotor and pad will wear faster due to less braking surface area than the drum system they replace. Since the rears only do 30% of the braking or less, they really downsized the size of the brakes back there, and they wear almost as fast as the fronts. I find they are very similar in wear between the front and rears on my 2000 Explorer w/ rear disc brakes. Also, the parking brake is a mini drum set-up inside the rear rotor.