YACT: Why do automakers still use drum brakes?

[DurocShark]

I see new vehicles with drums all the time. WTF?

I thought disk brakes were supposed to be much better. And it seems to me they would be cheaper to make (fewer parts) and cheaper to warranty (fewer things to break).

Is there some point where drums are actually superior to disk brakes?

 

[Eli]

When moisture is present outside the wheel? shrug.

 

[Ryan]

manufacturing costs -drums are still cheaper.

 

Duroc, you must take into account that front brakes do 75% of the stopping, the rears 25%, it is more economical to install drums on the rear for this one matter alone, not to mention the fact that converting/designing a emergency brake into a caliper is expensive.
You must also take into account that disc brakes require 4 times the fluid and 6 to 10 times the pressure to stop the vehicle compared to drum brakes, this is because of the large piston area of the caliper and due to the fact that drum brakes are self energising. (the shoes in drum brakes rotate slightly and cam outwards thus assistang in the braking action)


Did you catch all that buddy ?

 

[brxndxn]

I think the automakers install drum brakes just so people can laugh at the painted drum brakes through 19" rims on a ricer Honda Civic.

 

[Eli]

Originally posted by: Roger
Duroc, you must take into account that front brakes do 75% of the stopping, the rears 25%, it is more economical to install drums on the rear for this one matter alone, not to mention the fact that converting/designing a emergency brake into a caliper is expensive.
You must also take into account that disc brakes require 4 times the fluid and 6 to 10 times the pressure to stop the vehicle compared to drum brakes, this is because of the large piston area of the caliper and due to the fact that drum brakes are self energising. (the shoes in drum brakes rotate slightly and cam outwards thus assistang in the braking action)


Did you catch all that buddy ?

w00t! Always leave it to Roger to educate all us n00bs!

I should really get into the know about brakes and suspension and that kinda stuff. Too much attention on the engine/drivetrain.. mmm.. engines.. lol

 

[Insane3D]

Another reason might be that drums seem to last much longer than your average rotor. You may change the rotor a few times over a car's life, while the drum may get replaced once or twice, or not @ all.

*shrug*

It bugs me my GT still has drum brakes in the rear, but I've done some upgrades to the front, and hopefully within the coming year, I'll be installing this.



Edit:

If I was a rich man, I would love to put these on too... :Q

 

[StageLeft]

So, it's cheaper then hey?

I'm hoping to never have a car with drums again, so that I don't find myself ever forced to learn how to change them

 

Hey Eli

Forgot to mention that 4 wheel discs require a larger brake booster, a larger master cylinder piston bore and larger brake lines which also h increases the cost as well.

 

[DurocShark]

Welcome back Roger!!! :beer:

Do drum brake shoes/drums really last longer? Or do we just not notice when they go bad because the rears do such a small amount of the braking?

 

[thedarkwolf]

Originally posted by: Insane3D
Another reason might be that drums seem to last much longer than your average rotor. You may change the rotor a few times over a car's life, while the drum may get replaced once or twice, or not @ all.

*shrug*

It bugs me my GT still has drum brakes in the rear, but I've done some upgrades to the front, and hopefully within the coming year, I'll be installing this.



Edit:

If I was a rich man, I would love to put these on too... :Q

You don't need to be a rich man just go the junkyard route.
Mustang brake upgrades
As soon as I find a 94-95 mustang in the junkyard thats what I will be doing.

 

[Pacfanweb]

Originally posted by: Insane3D
Another reason might be that drums seem to last much longer than your average rotor. You may change the rotor a few times over a car's life, while the drum may get replaced once or twice, or not @ all.

*shrug*

It bugs me my GT still has drum brakes in the rear, but I've done some upgrades to the front, and hopefully within the coming year, I'll be installing this.



Edit:

If I was a rich man, I would love to put these on too... :Q

Your rear drum brakes last longer because they're on the rear. The fronts are doing the majority of the stopping.

 

[Pacfanweb]

Originally posted by: rbloedow
manufacturing costs - drums are still cheaper. 

Not to mention they are lighter on vehicles where the front bearings are still part of the rotor.
Probably even a bit lighter on vehicles with slip-ons, but not as much so.

 

[myusername]

It's unlikely that automakers had it in mind when using rear drums, but drums are more effective at braking while towing a trailer than discs.

 

[Zenmervolt]

Originally posted by: myusername
It's unlikely that automakers had it in mind when using rear drums, but drums are more effective at braking while towing a trailer than discs.

Uh, no. Towing or not towing has no effect on the amount of stopping power the brakes can generate. If drums are inferior when not towing, they are also inferior when towing.

Really, the big drawback with drums is fade. Drum brakes just don't dissipate heat as well and they overheat and lose effectiveness very quickly compared to discs.

ZV

 

[JupiterJones]

Originally posted by: DurocShark
I see new vehicles with drums all the time. WTF?

I thought disk brakes were supposed to be much better. And it seems to me they would be cheaper to make (fewer parts) and cheaper to warranty (fewer things to break).

Is there some point where drums are actually superior to disk brakes?

"Back in the day", when American car companies first started putting front disk brakes on cars, the conventional wisdom was that drums had more stopping power, and disk brakes braked more evenly. Thus the disk brakes were put on the front, so that under hard braking the car did not pull to one side, while leaving drums on the back to shorten stopping distance.

This was true at the time, probably due to the booster not being up to snuff when it came to the disk brakes. Four Wheel Disk systems were somethig you only heard about on European cars, and most people did not believe was superior outside the racetrack (where the tendency of drums to overheat would become a factor -- reason Shelby GT350's had side scoops to cool the rear brakes).

This all may not be right, but it's what we all thought back then.

Today, I would assume that it is simply cheaper. Drum's today are better than disk brakes back then.

Don

 

Do drum brake shoes/drums really last longer? Or do we just not notice when they go bad because the rears do such a small amount of the braking?

Read my lips ;

Front brakes do 75% of the braking (weight transfer)

Rear brakes do 25% of the braking


This is one of the reasons they last longer, the other reason ?
Drum brakes have three to ten times the friction surface area that disc brakes do, thus they last longer..

 

[Insane3D]

Originally posted by: thedarkwolf

Originally posted by: Insane3D

Another reason might be that drums seem to last much longer than your average rotor. You may change the rotor a few times over a car's life, while the drum may get replaced once or twice, or not @ all.



*shrug*



It bugs me my GT still has drum brakes in the rear, but I've done some upgrades to the front, and hopefully within the coming year, I'll be installing this.







Edit:



If I was a rich man, I would love to put these on too... :Q

You don't need to be a rich man just go the junkyard route.

Mustang brake upgrades

As soon as I find a 94-95 mustang in the junkyard thats what I will be doing.

Thanks for the link. I knew about the Turbo Coupe brakes for the rear, but it's almost more of a PITA to go that route. Also, I just put in new superior axles, and that link seems to say you need new ones for the conversion. The SSBC kit may be more, but I would prefer the direct fit than junkyard parts route. Also, I've alreayd done a few upgrades that have made front braking much better.

I replaced the stock 60mm calipers with the ones from the older Lincoln LSC's that have the 73mm piston. The 73mm calipers were only like $25 each from the local auto parts store. I replaced all the brake line to the wheels with those stainless steel lines, used the aluminum caliper bushings in the front, and I threw on some cross drilled rotors. I have used the VGX pads from Summit Racing the last couple changes as they seem to wear evenly, and use a very fine grind of brake material that doesn't tear up the rotor since you can't really turn the cross drilleds. I also installed the FMS brake proportioning valve to increase the bias to the front.

Also, I have a couple friends who have done the conversion, and they both commented that it really doesn't make the car stop that much better, it's just a bit more even braking, with less "nose dive effect". Since I did all my suspension upgrades, I don't really get that anymore.

Thanks for the link though...

 

[JeffreyLebowski]

Originally posted by: Roger

Do drum brake shoes/drums really last longer? Or do we just not notice when they go bad because the rears do such a small amount of the braking?

Read my lips ;

Front brakes do 75% of the braking (weight transfer)

Rear brakes do 25% of the braking


This is one of the reasons they last longer, the other reason ?
Drum brakes have three to ten times the friction surface area that disc brakes do, thus they last longer..

true the front do more braking, but ride in a 3rd gen firebird or camaro with drum rear and slam the brakes, and do it in a all disc 3rd gen. You will see a huge difference in stopping power.

Once i get a job my GTA will be converted over to an all disc setup

 

[myusername]

Originally posted by: Zenmervolt

Originally posted by: myusername
It's unlikely that automakers had it in mind when using rear drums, but drums are more effective at braking while towing a trailer than discs.

Uh, no. Towing or not towing has no effect on the amount of stopping power the brakes can generate. If drums are inferior when not towing, they are also inferior when towing.

Really, the big drawback with drums is fade. Drum brakes just don't dissipate heat as well and they overheat and lose effectiveness very quickly compared to discs.

ZV

son of a :frown:

I remember reading a linked article on this in another forum in a disc conversion thread. It posited that the weight transfer of the trailer would cause a set of rear drums to actually become more effective. It didn't advocate drum brakes, just pointed out the theory.

Unfortunately the forum archives don't go back that far, and I haven't found anything to support it on google yet, so I apologize for the misinformation

 

[OS]

Originally posted by: Roger
Duroc, you must take into account that front brakes do 75% of the stopping, the rears 25%, it is more economical to install drums on the rear for this one matter alone, not to mention the fact that converting/designing a emergency brake into a caliper is expensive.
You must also take into account that disc brakes require 4 times the fluid and 6 to 10 times the pressure to stop the vehicle compared to drum brakes, this is because of the large piston area of the caliper and due to the fact that drum brakes are self energising. (the shoes in drum brakes rotate slightly and cam outwards thus assistang in the braking action)

Did you catch all that buddy ?

The stuff I've read puts the ratio even less, 20%-15% of stopping force is from the rear brakes. I bet that for stock cars, you can probably get better braking performance from stickier tires and stiffer suspension than rear discs.

In fact, too much braking at the rear wheels supposedly can create a car that dangerous to drive. If the rear tires lock up before the fronts, the car will behave unpredictably during braking.

 

[BCYL]

My car has front discs and rear drum brakes... I just had to replace my front brake pads last week becuz they were all used up, but my rear drums still have 60% left...

 

[OS]

Originally posted by: JeffreyLebowski
true the front do more braking, but ride in a 3rd gen firebird or camaro with drum rear and slam the brakes, and do it in a all disc 3rd gen. You will see a huge difference in stopping power.

Once i get a job my GTA will be converted over to an all disc setup

Did both cars have the same curb weight, same wheels, same tires, same suspension setup, and same front rotor size?

 

[Iron Woode]

Originally posted by: OS

Originally posted by: JeffreyLebowski
true the front do more braking, but ride in a 3rd gen firebird or camaro with drum rear and slam the brakes, and do it in a all disc 3rd gen. You will see a huge difference in stopping power.

Once i get a job my GTA will be converted over to an all disc setup

Did both cars have the same curb weight, same wheels, same tires, same suspension setup, and same front rotor size?

There be the rub.

People think their sports cars or performance cars have awesome brakes. The reality is: it depends.

The brakes on my 1987 Crown Vic are huge. I used to say the rotors were bigger than the rims on a civic. LOL.

I can stop very quickly and safely because bigger is better when it comes to brakes. Mopar put 4-wheel drum brakes on the 1968 Road Runner/Super Bee because it was cheaper than disk/drum. However they gave the cars 12 inch x 3 inch drums with huge cooling fins to allow excellent heat dissapation. Brake fade was almost eliminated on these cars.

Drums maybe old tech, but they are very effective.

 

[db]

Since this thread has drifted all over the place, I'll throw my 2 cents in and say that disc brakes also do better when wet than drum brakes--they "squeegie" the water off the rotor, whereas drums can take some time to "dry" out.