Disc Brakes Vs Drum Brakes - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 03-21-2009, 12:08 AM   #1
Registered Member
 
Join Date: Aug 2008
Posts: 9
Country: United States
Disc Brakes Vs Drum Brakes

Could you pls tell me the difference between Disc brakes and Drum brakes? All i know about them is that Disc brakes are better than Drum brakes.... but what's the reason behind it?



----
"In less enlightened times, the best way to impress women was to own a hot car. But women wised up and realized it was better to buy their own hot cars so they wouldn't have to ride around with jerks." -Scott Adams
__________________

wendywindy is offline   Reply With Quote
Old 03-21-2009, 01:20 AM   #2
Registered Member
 
Join Date: Mar 2009
Posts: 1,139
Country: United States
My understanding is that drum brakes are cheaper than disc brakes. Check out these links: disc and drum.
__________________

__________________


Main Entry: co de pen dence - see codependency
co de pen den cy
Pronunciation: \kō-di-ˈpen-dən(t)-sē\
Function: noun
Date: 1979

: a psychological condition or a relationship in which a person is controlled or manipulated by another who is affected with a pathological condition (as an addiction to alcohol or heroin) ; broadly : dependence on the needs of or control by another
GasSavers_maximilian is offline   Reply With Quote
Old 03-21-2009, 01:49 AM   #3
Site Team
 
Join Date: Dec 2006
Posts: 656
Country: United States
Actually from an MPG perspective, theoretically drum brakes will have less drag than disc brakes, for better MPG. However the difference is probably not measurable.

My old Buick originally came with drum brakes at all four corners.

The principle of operation is the same - you have a friction material pressed against a steel surface to create drag, which slows the vehicle. Disc brakes have a rotor (disc-shaped) and has a pad on each side which is squeezed against the rotor to slow down the vehicle. Drum brakes, on the other hand, have the pads on the inside of a cylindrical surface to create drag.

-BC
__________________
Think you are saving gas? Prove it by starting a Gas Log, then conduct a proper experiment.
bobc455 is offline   Reply With Quote
Old 03-21-2009, 01:55 AM   #4
Registered Member
 
Join Date: Mar 2009
Posts: 1,139
Country: United States
Quote:
Originally Posted by bobc455 View Post
Actually from an MPG perspective, theoretically drum brakes will have less drag than disc brakes, for better MPG.
I meant from a manufacturer's cost perspective. Beats me on mpg.
__________________


Main Entry: co de pen dence - see codependency
co de pen den cy
Pronunciation: \kō-di-ˈpen-dən(t)-sē\
Function: noun
Date: 1979

: a psychological condition or a relationship in which a person is controlled or manipulated by another who is affected with a pathological condition (as an addiction to alcohol or heroin) ; broadly : dependence on the needs of or control by another
GasSavers_maximilian is offline   Reply With Quote
Old 03-21-2009, 02:13 AM   #5
Site Team
 
Join Date: Dec 2006
Posts: 656
Country: United States
Quote:
Originally Posted by wendywindy View Post
but what's the reason behind it?
I forgot to answer the original question, sorry...

Disc brakes are "better" because they are more exposed to atmosphere, and thus less susceptible to heat fade. So they are "better" for racecars and such, but for your average driver that isn't really a factor.

Disc brakes are easier to work on IMO. But the hardware is simpler/cheaper for OEMs.

-BC
__________________
Think you are saving gas? Prove it by starting a Gas Log, then conduct a proper experiment.
bobc455 is offline   Reply With Quote
Old 03-21-2009, 02:17 AM   #6
Registered Member
 
Join Date: Mar 2009
Posts: 1,139
Country: United States
I hate working on drums. Retracting the pads from grooves in the rotors can be a real headache, especially when the parts get rusted by all the salt that's used around here.

Apparently drums lend themselves better to being part of the emergency brake system.
__________________


Main Entry: co de pen dence - see codependency
co de pen den cy
Pronunciation: \kō-di-ˈpen-dən(t)-sē\
Function: noun
Date: 1979

: a psychological condition or a relationship in which a person is controlled or manipulated by another who is affected with a pathological condition (as an addiction to alcohol or heroin) ; broadly : dependence on the needs of or control by another
GasSavers_maximilian is offline   Reply With Quote
Old 03-21-2009, 06:44 AM   #7
Registered Member
 
theholycow's Avatar
 
Join Date: Apr 2008
Posts: 6,624
Country: United States
Send a message via ICQ to theholycow Send a message via AIM to theholycow Send a message via MSN to theholycow Send a message via Yahoo to theholycow
Well, I too hate working on drum brakes. When I open them up they look like a crazy pile of clockwork springs/gears/levers that I'll never be able to return to their original configuration.

They're never anywhere near as simple as this:


or this:


for me.
__________________
This sig may return, some day.
theholycow is offline   Reply With Quote
Old 03-21-2009, 07:23 AM   #8
Registered Member
 
Join Date: Mar 2009
Posts: 1,139
Country: United States
Quote:
Originally Posted by theclencher View Post
Drums don't have pads and rotors LOL
See how strong my bias is?
__________________


Main Entry: co de pen dence - see codependency
co de pen den cy
Pronunciation: \kō-di-ˈpen-dən(t)-sē\
Function: noun
Date: 1979

: a psychological condition or a relationship in which a person is controlled or manipulated by another who is affected with a pathological condition (as an addiction to alcohol or heroin) ; broadly : dependence on the needs of or control by another
GasSavers_maximilian is offline   Reply With Quote
Old 03-21-2009, 07:42 AM   #9
Senior Member
 
Join Date: Jul 2010
Posts: 278
Country: United States
Location: CT
Drum brakes have a self energizing mechanism... Basically the action of braking with a drum brake forces the pads outward, which makes them brake even harder, which forces the pads outward which makes them brake even harder ect ect... They work great with a non-power brake system, such as the emergency brake, or old non-power brakes.

However, they are very susceptible to mechanical fade (when the drum gets so hot it expands away from the pads), and are rendered short term useless by water in them. It's the reason why engine braking was VERY necessary on long hills, because if you rode your service brakes the whole time with drums, your foot would go to the floor and you'd have no brakes at all.

Disc brakes don't provide as much braking force in relation to the input force, so they need much higher input force in order to be effective, hence the need for power brakes. However, they are far simpler, automatically self adjusting, have far better cooling properties so they're less susceptible to heat fade, are not at all susceptible to mechanical fade, and water is instantly squeegeed off so as to proved no noticeable reduction of braking ability. All in all, they are far safer, better, and cheaper than drum brakes.

The reason drum brakes are still used in the rear of cars today is due to the fact that disc brakes make very poor parking brakes. You either have to have a very complex screw/spring system in the rear caliper to actuate it when you pull the parking brake cable, or I've seen many rear discs that have a small drum brake in the hub.


Hope that helped!
Wyldesoul is offline   Reply With Quote
Old 03-21-2009, 08:15 AM   #10
Registered Member
 
Join Date: Mar 2009
Posts: 93
Quote:
Originally Posted by Biffmeistro View Post
Drum brakes have a self energizing mechanism... Basically the action of braking with a drum brake forces the pads outward, which makes them brake even harder, which forces the pads outward which makes them brake even harder ect ect... They work great with a non-power brake system, such as the emergency brake, or old non-power brakes.

However, they are very susceptible to mechanical fade (when the drum gets so hot it expands away from the pads), and are rendered short term useless by water in them. It's the reason why engine braking was VERY necessary on long hills, because if you rode your service brakes the whole time with drums, your foot would go to the floor and you'd have no brakes at all.

Disc brakes don't provide as much braking force in relation to the input force, so they need much higher input force in order to be effective, hence the need for power brakes. However, they are far simpler, automatically self adjusting, have far better cooling properties so they're less susceptible to heat fade, are not at all susceptible to mechanical fade, and water is instantly squeegeed off so as to proved no noticeable reduction of braking ability. All in all, they are far safer, better, and cheaper than drum brakes.

The reason drum brakes are still used in the rear of cars today is due to the fact that disc brakes make very poor parking brakes. You either have to have a very complex screw/spring system in the rear caliper to actuate it when you pull the parking brake cable, or I've seen many rear discs that have a small drum brake in the hub.


Hope that helped!
^^^ That is the absolute best explanation I've seen and 100% correct.

Drum brakes actually are better for 2 reasons, they clamp harder and they are better for fuel economy because they have less resistance and rotational weight. However, the reason discs are used today is for their fade resistance. Drums do not dissipate heat as well as rotors. Take identical cars with the sole exception of front drums vs front discs and the drum brake car will stop shorter the first time. After that, the disc brake car will stop shorter.
__________________

GasSavers_NovaResource is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Adding the 2013 Ford Fusion Energi? JDsEnergi Fuelly Web Support and Community News 1 06-27-2013 01:49 PM
Feature request: input "validation" override Volta Fuelly Web Support and Community News 8 08-20-2008 01:20 AM
Fleet/Brand metrics? handruin Fuelly Web Support and Community News 1 08-19-2008 02:50 PM
New Michigander bbanzai Introduce Yourself - New member Welcome 4 05-20-2008 06:04 PM
Any Toronto Peeps here? bbgobie General Discussion (Off-Topic) 0 06-15-2007 10:11 AM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 05:26 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.