# Why drum brakes on cars? **URL:** \ **Category:** Factual Questions\ **Created:** [August 11, 2002, 11:37am UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391 "2002-08-11T11:37:42Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![kferr](https://avatars.discourse-cdn.com/v4/letter/k/71e660/32.png) [@kferr](https://boards.straightdope.com/u/kferr)\ **Post date:** [August 11, 2002, 11:37am UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/1 "2002-08-11T11:37:42Z")
Is is generally acknowledged that disc brakes are more effective than drum brakes. Some cars have disc brakes front and rear, and some (usually smaller) cars still have drum brakes on the rear. I’m wondering, why do they still use drum brakes? Some of the answers I came up with are: **They’re cheaper**. But then they’d have to be really cheap to justify the cost of a drum brake factory in addition to the disc brake factory. **It prevents rear wheel lock-up**. But then even tiny new cars these days have ABS so this shouldn’t be an issue. So what’s the story? What is the real engineering and economic reason for using drum brakes? ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [August 11, 2002, 12:35pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/2 "2002-08-11T12:35:07Z")
I think part of the reason is it provides balance between the front and rear. the rear needing less stopping force gets the less effective braking system ---
**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\ **Post date:** [August 11, 2002, 1:03pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/3 "2002-08-11T13:03:06Z")
- - - Drum brakes _are_ cheaper to make than disk brakes; the only advantage of using drum brakes is lower cost. … - And you’ve got it backwards: the _drum_ brake factories came first, _then_ the disk brake factories came along. Disc brakes work better, but it was a simple case of them not wanting to shut down the drum brake factories, because car companies still want to use drum brakes. Lots of new cars in the US still use rear drum brakes. ~ ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [August 11, 2002, 1:13pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/4 "2002-08-11T13:13:13Z")
If the hand brake still connects to the rear wheels (which it does in most cars), it does function better with a better “locking” on drum brakes (depending where the pivot point of the shoe is, of course…some manufacturers put the pivot point backwards). It is, as was mentioned, easier to balance braking force for everyday control with drums on the rear and discs on the front. ---
**Author:** ![Mr.Moto](https://avatars.discourse-cdn.com/v4/letter/m/9de0a6/32.png) [@Mr.Moto](https://boards.straightdope.com/u/Mr.Moto)\ **Post date:** [August 11, 2002, 1:14pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/5 "2002-08-11T13:14:45Z")
Also, cars with four-wheel disc brakes have drum brakes too. The drum brakes are in the back and used as the parking brake. Drum brakes are great parking brakes, disc brakes don’t work well in this role. Since you’re going to have the drum brakes in the rear anyway, you might as well use them as the main rear brakes when it is feasible to do so. ---
**Author:** ![Anachronism](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@Anachronism](https://boards.straightdope.com/u/Anachronism)\ **Post date:** [August 11, 2002, 1:27pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/6 "2002-08-11T13:27:08Z")
Not sure if this an issue but drum brakes can work without power assist. Disk brakes require power to work. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [August 11, 2002, 2:08pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/7 "2002-08-11T14:08:23Z")
[qoute]Disk brakes require power to work. [/quote] My Yamaha has disc brakes, and there is no power assist. I’m pretty sure my Porsche didn’t have power assist. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 11, 2002, 2:10pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/8 "2002-08-11T14:10:51Z")
Is there a simple explanation on why drum brakes are cheaper? Disc brakes look pretty simple to me. ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [August 11, 2002, 2:18pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/9 "2002-08-11T14:18:27Z")
**scr4** , this is just a guess, but drum brakes require only one casting for the brake drum; everything else can be stamped out of sheet metal. Disc brakes need two or three castings, one for the disc and one or two for the caliper. The hanger also needs to be made out of metal plate. ---
**Author:** ![LouisB](https://avatars.discourse-cdn.com/v4/letter/l/dfb087/32.png) [@LouisB](https://boards.straightdope.com/u/LouisB)\ **Post date:** [August 11, 2002, 2:23pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/10 "2002-08-11T14:23:36Z")
> [@](#): > > \*Originally posted by Anachronism \* > \*\*Not sure if this an issue but drum brakes can work without power assist. Disk brakes require power to work. \*\* This is not true. Why would disk brake systems require power assist? These systems are hydraulic systems, identical in all respects to drum brake systems. ---
**Author:** ![Mr.Moto](https://avatars.discourse-cdn.com/v4/letter/m/9de0a6/32.png) [@Mr.Moto](https://boards.straightdope.com/u/Mr.Moto)\ **Post date:** [August 11, 2002, 3:04pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/11 "2002-08-11T15:04:05Z")
Both discs and drums are hydraulic systems, usually power assisted. Drum brakes are very easy to operate using a cable pull that forces the shoes apart, making it very inexpensive to have an emergency and parking brake. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [August 11, 2002, 3:12pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/12 "2002-08-11T15:12:59Z")
> [@](#): > > \*Originally posted by Anachronism \* > \*\*Not sure if this an issue but drum brakes can work without power assist. Disk brakes require power to work. \*\* This is not accurate. Power/no power has nothing to do with the type of brakes. And as a stand-out example, the FIAT X 1/9 was well known for it’s nice and effective brakes, and it had absolutely _no_ power assist on it. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [August 11, 2002, 3:14pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/13 "2002-08-11T15:14:13Z")
> [@](#): > > \*Originally posted by cornflakes \* > \*\ ***scr4** , this is just a guess, but drum brakes require only one casting for the brake drum; everything else can be stamped out of sheet metal. Disc brakes need two or three castings, one for the disc and one or two for the caliper. The hanger also needs to be made out of metal plate. \*\* No, the discs on several cars I have worked on were a single forging or casting. The thing is that the disc brake _caliper_ is often a somewhat expensive item. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [August 11, 2002, 3:15pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/14 "2002-08-11T15:15:16Z")
Sorry, **cornflakes** , I mis-read your post. :o ---
**Author:** ![zwede](https://avatars.discourse-cdn.com/v4/letter/z/ac91a4/32.png) [@zwede](https://boards.straightdope.com/u/zwede)\ **Post date:** [August 11, 2002, 3:20pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/15 "2002-08-11T15:20:34Z")
With drum brakes the pivoting of the brake shoe will assist in brake force. This enables drumbrake systems to operate fairly well without a brake booster. Although it is true that you can have 4 wheel disc brakes with no booster, the pedal effort will be very high compared to drums. On a small, light, car you can still get away with manual discs. Hevy cars will require a booster. The only advantage to drum brakes (except the lower cost) is that they are not sensitive to water. Disc brakes have a tendency to not work well when driving through deep puddles. The big problem with drum brakes is that the heat is retained inside the drum, making them overheat during hard use. Markus ---
**Author:** ![kferr](https://avatars.discourse-cdn.com/v4/letter/k/71e660/32.png) [@kferr](https://boards.straightdope.com/u/kferr)\ **Post date:** [August 11, 2002, 3:25pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/16 "2002-08-11T15:25:26Z")
Thanks for all the answers so far. About parking/hand brakes, my current car has rear disks and the hand brake operates the caliper, there isn’t an extra drum. I learned all about the working of the hand brake after water got into the cable housing and froze the hand brake on on a really cold winter morning. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [August 11, 2002, 3:25pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/17 "2002-08-11T15:25:52Z")
> [@](#): > > Disk brakes require power to work. even though this one was answered I just had to add that I had a car ('80 dodge omni 024) that had no power brakes (no p/s either) it was a front disk/rear drum and it worked easily enough. I was very surprized when I got a 85 plym turismo a few years later and found that they had power brakes - on such a light car there is really no need and IMHO more dangerous since loss of power assist makes braking much harder. just wanted to point out that manual brakes do work very good on low end cars. ---
**Author:** ![bernse](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@bernse](https://boards.straightdope.com/u/bernse)\ **Post date:** [August 11, 2002, 3:40pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/18 "2002-08-11T15:40:07Z")
> [@](#): > > \*Originally posted by Mr. Moto \* > \*\*Also, cars with four-wheel disc brakes have drum brakes too. The drum brakes are in the back and used as the parking brake. > > Drum brakes are great parking brakes, disc brakes don’t work well in this role. > > Since you’re going to have the drum brakes in the rear anyway, you might as well use them as the main rear brakes when it is feasible to do so. \*\* Whaaat? A vehicle with 4 wheel disc has drum brakes in the back for a _parking brake_? Where did you get that idea from? Do you have an example of this? 😕 I’ve heard of vehilcles having a drum brake on the _driveshaft_ for a parking brake, but even then, none of those vehicles had disc on the rear wheels either. Disc brakes can work just fine as parking brakes. ---
**Author:** ![brad\_d](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@brad\_d](https://boards.straightdope.com/u/brad_d)\ **Post date:** [August 11, 2002, 4:50pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/19 "2002-08-11T16:50:06Z")
> [@](#): > > \*Originally posted by Mr. Moto \* > \*\*Also, cars with four-wheel disc brakes have drum brakes too. The drum brakes are in the back and used as the parking brake. > \*\* A small “sub-drum” used only as the parking brake is one method of doing it on 4-wheel-disc cars, but not the only one. I’ve no personal experience, but my _Haynes Automotive Brake Manual_ nicely describes three ways to deal with it (going from memory here):[ul][li]cable actuation of the main caliper on the rear wheels[_]small caliper (in addition to the main one) used only as the parking brake[_]a “top-hat” geometry to the drum: the hat “brim” is the disc, while the insides of the “stovepipe” house a very small drum brake that serves as a parking brake[/ul]They don’t mention specifically how common each of these methods are, but imply that you can find examples of all three without much effort.[/li] This same manual also suggests that power assist proved necessary _from a practical perspective_ to make disc brakes on road cars feasible. Sure, disc brakes work just fine without it, but like **zwede** said pedal forces required would be excessive by the standards we’ve gotten used to - at least with disc brakes of reasonable size. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [August 11, 2002, 5:17pm UTC](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391/20 "2002-08-11T17:17:42Z")
In retrospect, the Porsche may have had a boost pump for the brakes; but the Yamaha definitely doesn’t. [Next page](https://boards.straightdope.com/t/why-drum-brakes-on-cars/123391.md?page=2)