Why Drum Brakes?

[triangleforge]

After spending most of yesterday covered in sweat and brake dust, all the while cursing at all manner of springs that you can't reach and spring tools that can't actually remove or replace them, I had to wonder - why do drum brakes even still exist for most of us? Backstory - I had to call in to my summer job fixing golf carts (the joys of a high school teaching career) to say I'd be an hour late as replacing the shoes on my girlfriend's Kia was 3/4 done in 3x the time I'd expected it to take. He said no problem - then presented me with a couple of brake replacements on carts when I rolled into the shop. 

The Kia was a piece of work, as apparently one of the primary engineering objectives was to make it impossible to work on. It was a whole mess of powerful springs in awkward places, most of which had to be set blind and on which none of the impressive array of brake spring tools I had at my disposal (my boss at the golf car place used to be the local Snap-On dealer, so...) would work. The E-brake attachment was one of the funkiest puzzles I've ever seen, one I finally solved with a pair of Vice Grips, C-Clip pliers, two sets of hands, and a whole lot of trying over, and over, and over.

The golf carts were easier - lighter to sling the parts around, at least - but adjustment was a pisser. Because torquing the wheel onto the hub changed EVERYTHING about the adjustment, you couldn't get them set with the wheel off... but you couldn't reach the adjusters with the wheel on.

And with every smashed knuckle and spring that went flying across the shop, I remembered life with my 1973 Land Cruiser with drums at all four corners. Even with the brakes in tip-top condition & adjustment, stopping was a leisurely affair in that truck, and after any stream crossing I'd just assume I had no brakes at all. Drum brakes just suck.

I'm sure there are better ways to do both of these jobs than I did and Kia special service tools that would be in a dealer's arsenal (but probably not in most professional shops), but every single one of the professional mechanics I asked despises working on drum brakes and can't think of a single reason why they're still used so widely on passenger cars.

Running an E-Brake with a cable may be relatively easier with drums, but plenty of engineers have figured that one out. Drag racers used to prefer them because they used to have lower rotating mass and you could set them up with zero drag (which has nothing to do with the design needs of a Kia minivan).

So why do we still have to deal with these pieces of cutting edge 19th century technology? Discs are cheaper to manufacture, take less labor to install at the factory, cost less for the dealer to service, perform radically better and, perversely, would allow car makers to charge a little bit MORE for a performance upgrade for at least a few years.

Why drum brakes in the 21st Century?

[DarkMonster620]

After spending most of yesterday covered in sweat and brake dust, all the while cursing at all manner of springs that you can't reach and spring tools that can't actually remove or replace them, I had to wonder - why do drum brakes even still exist for most of us? Backstory - I had to call in to my summer job fixing golf carts (the joys of a high school teaching career) to say I'd be an hour late as replacing the shoes on my girlfriend's Kia was 3/4 done in 3x the time I'd expected it to take. He said no problem - then presented me with a couple of brake replacements on carts when I rolled into the shop. 

The Kia was a piece of work, as apparently one of the primary engineering objectives was to make it impossible to work on. It was a whole mess of powerful springs in awkward places, most of which had to be set blind and on which none of the impressive array of brake spring tools I had at my disposal (my boss at the golf car place used to be the local Snap-On dealer, so...) would work. The E-brake attachment was one of the funkiest puzzles I've ever seen, one I finally solved with a pair of Vice Grips, C-Clip pliers, two sets of hands, and a whole lot of trying over, and over, and over.

The golf carts were easier - lighter to sling the parts around, at least - but adjustment was a pisser. Because torquing the wheel onto the hub changed EVERYTHING about the adjustment, you couldn't get them set with the wheel off... but you couldn't reach the adjusters with the wheel on.

And with every smashed knuckle and spring that went flying across the shop, I remembered life with my 1973 Land Cruiser with drums at all four corners. Even with the brakes in tip-top condition & adjustment, stopping was a leisurely affair in that truck, and after any stream crossing I'd just assume I had no brakes at all. Drum brakes just suck.

I'm sure there are better ways to do both of these jobs than I did and Kia special service tools that would be in a dealer's arsenal (but probably not in most professional shops), but every single one of the professional mechanics I asked despises working on drum brakes and can't think of a single reason why they're still used so widely on passenger cars.

Running an E-Brake with a cable may be relatively easier with drums, but plenty of engineers have figured that one out. Drag racers used to prefer them because they used to have lower rotating mass and you could set them up with zero drag (which has nothing to do with the design needs of a Kia minivan).

So why do we still have to deal with these pieces of cutting edge 19th century technology? Discs are cheaper to manufacture, take less labor to install at the factory, cost less for the dealer to service, perform radically better and, perversely, would allow car makers to charge a little bit MORE for a performance upgrade for at least a few years.

Why drum brakes in the 21st Century?

they are supposed to keep costs lower . . . labour costs go up . . . ask rotor head . . .  I HATE DRUM BRAKES !!!

[Popeye the Sailor]

Rears do like 10% of the braking so don't see a lot of wear, and it's substantially easier to install one brake that functions as both a regular and parking brake vs installing a set of discs and a separate caliper for the parking brake. Especially considering most people don't use the parking brake and the rear brakes are basically along for the ride.

Performance improvement is minimal with the change, esp on a budget minivan. As far as cheaper to work on-this is just the factories way of making sure their dealer service departments make some money.



I can probably paraphrase Kia's unofficial stance for ya:


"It's cheaper-make the beast with two backs you"


Or, if they don't feel like consulting a bean counter, "make the beast with two backs you".


Please let me now if you have any other questions re: modern day manufacturing/corporate America. 

[Triple J]

I can probably paraphrase Kia's unofficial stance for ya:


"It's cheaper-make the beast with two backs you"


Or, if they don't feel like consulting a bean counter, "make the beast with two backs you".

This is awesome! 

[Bick]

Craslo sends me frequent PM's asking if he can come back to town and fix my brakes again.



Sometimes a have to question what he means by "FIX"

[DarkMonster620]

jajahajajajajajajajaja

[the_Journeyman]

My Dakota came with drum rear instead of disc.  Dodge said because I had the towing package and heavy duty suspension I got the drums instead of the discs.  They're explanation was due to the truck being equipped for heavier hauling with the towing equipment and heavier suspension and that drums are much better and managing a heavy load.

It makes some sense, since the air brakes that most buses and heavy trucks & tractor trailers are drum (air instead of hydraulic of course).  However, I don't image the heavy load part applies to any Kia.

JM

[Popeye the Sailor]

My Dakota came with drum rear instead of disc.  Dodge said because I had the towing package and heavy duty suspension I got the drums instead of the discs.  They're explanation was due to the truck being equipped for heavier hauling with the towing equipment and heavier suspension and that drums are much better and managing a heavy load.

And you believed them? 


Next up on Corporate Mothermake the beast with two backser: we'll teach you how to convince the peons that the bugs are features!

Nobody buys a Dakota to tow with. They had a deal on $5 trailer hitches that week and added on a $500 tow package. Likely they added it to every Dakota made so they could charge more and give you no option about buying said package.


They're all evil.

We should shun Randimus on principle.

[Triple J]

My Dakota came with drum rear instead of disc.  Dodge said because I had the towing package and heavy duty suspension I got the drums instead of the discs.  They're explanation was due to the truck being equipped for heavier hauling with the towing equipment and heavier suspension and that drums are much better and managing a heavy load.

Sounds like BS to me. My Chevy has a 17,000 lb tow capacity, and the truck itself weighs about 7,500 lbs...discs all around.

[the_Journeyman]

Nobody buys a Dakota to tow with.

I do.  Plenty, and usually push it's ratings both in towing and payload.

Sounds like BS to me. My Chevy has a 17,000 lb tow capacity, and the truck itself weighs about 7,500 lbs...discs all around.

Heavy trucks have drums.  Our bus mechanics say that drums are more durable and lower maintenance than discs on heavy stuff.  I've seen a few motor coaches with front air powered discs, but not many.

JM

[triangleforge]

I have no doubt that corporate bean counters could not care less about my sweat and imaginative cursing. The thing I don't get is that discs (plebeian, simple things rather than high performance parts) are cheaper than drums. For the Kia minivan in question, the aftermarket rotors are $45, while the discs are $55. Granted that's aftermarket, but I don't imagine the cost differential goes the other way with OEM parts.

And if corporations have little regard for the consumer, just think how much less they have for the line workers who put the stuff together and his/her desire for full employment. Even with a professional auto worker using very specialized tools (or for that matter, an assembly robot) is going to take longer to put together a drum brake than a disc on the assembly line. More parts, more steps, more fussy bits to line up. 

I get that long haul trucks and buses have different needs, along with professionals who always do the service. Again, I'm not hoping that Detroit/Seoul/Toyota City (yes, it's a place) will ever care a whit about me and my problems. I still just don't get how drums are still the cheaper alternative.

[ducpainter]

I have no doubt that corporate bean counters could not care less about my sweat and imaginative cursing. The thing I don't get is that discs (plebeian, simple things rather than high performance parts) are cheaper than drums. For the Kia minivan in question, the aftermarket rotors are $45, while the discs are $55. Granted that's aftermarket, but I don't imagine the cost differential goes the other way with OEM parts.

And if corporations have little regard for the consumer, just think how much less they have for the line workers who put the stuff together and his/her desire for full employment. Even with a professional auto worker using very specialized tools (or for that matter, an assembly robot) is going to take longer to put together a drum brake than a disc on the assembly line. More parts, more steps, more fussy bits to line up. 

I get that long haul trucks and buses have different needs, along with professionals who always do the service. Again, I'm not hoping that Detroit/Seoul/Toyota City (yes, it's a place) will ever care a whit about me and my problems. I still just don't get how drums are still the cheaper alternative.

Spoken like an artist.

[Popeye the Sailor]

Spoken like an artist.

[Howie]

Most drum brakes have an advantage for stopping large vehicles by what is called servo action, hard to put into words, but google will help those whom are curious.  As the shoe material contacts the drum the leading, or, in the case of the Bendix (duo servo) type brake, both shoes wedge into the drum exerting more force.  A good example is an old high performane bike with four leading shoe drum up front. Properly adjusted?  Instant lock up.  Disc brakes do not do this.  Power brakes make servo action not needed, and sometimes undesirable.  Drum brakes also work better as a parking brake because of servo action.  This is why some heavy vehicles with rear discs use a mechanical drum brake integrated into the rotor as a parking brake.

In today's world of power brakes and electrohydraulicilly applied parking brakes not much justification for cars and light trucks.  ABS also works much better with disc brakes.  Needless to say lack of mechanical fade (drum expansion) and water fade are additional benefits.

Back to the Kia in question.  Most likely $$$.  Disc brakes become more expensive once you incorporate a parking brake plus you don't get to use up the leftover parts on the shelf.

To save the curious the work:
http://www.hemmings.com/hmn/stories/2013/09/01/hmn_feature19.html
https://en.wikipedia.org/wiki/Single-leading-shoe_drum_brake

[the_Journeyman]

This is why some heavy vehicles with rear discs use a mechanical drum brake integrated into the rotor as a parking brake.

My dad's Silverado had that exact setup for the parking brake.

JM