Disk brakes vs. drums.

[Demon-Xanth]

It's generally agreed upon that in cars, disk brakes stop a car faster than drums. I have yet to figure out why since drums have better heat dissipation, more surface area, and more leverage than disks. So why do the disk brakes work better?

 

[RagingBITCH]

Drum brakes have better heat dissipation? What?

 

[Demon-Xanth]

Ragingbitch next time you look at a drum, notice the heat fins all over the outer rim. There's alot of surface area there. 125 in^2 on a flat drum that's 10"x4" (not including the face) vs. 50 in^2 for a disk that's 10" diameter and 4" of surface

 

[Demon-Xanth]

Note that big rigs use drums for the reasons I listed.

 

The shoes inside the drums are enclosed by the drum, thus less cooling, heat is trapped inside the drum.

 

[Demon-Xanth]

Okay. That makes sense.

 

[Vic]

I'm no expert on this, but one advantage of disc brakes that I know of is that they are self-cleaning. Nothing like going through a puddle of water in a car with 4 wheel drums and then not being able to stop...

 

[gogeeta13]

Disk breaks are superior because they apply friction/force perpendicular to the rotor's movement. In a drum, the friction is applied on the inner surface of the drum, going int he same direction as the movement. Disk brakes are just vastly superior in every way. The pad, rotor and caliper all get open air exposure.

 

[DT4K]

Is it hard to take drum brakes apart and clean them?

The back brakes on my van were squealing. I had them checked out because I thought they needed replaced. The guy said they were fine, he just had to clean them off. But now, a couple months later, they are making squealing and grinding noises again.

 

[DivideBYZero]

Disc brakes have better modulation/are less prone to locking than Drums AFAIK.

 

[Bulk Beef]

Not so sure about the "more surface area" part either. Shoes usually don't make full contact, which leads to another disadvantage of drums - lack of progression.

 

Disc brakes have one failing, they require a lot more line pressure to activate compared to drum brakes which are self energizing.
(The shoes upon contact with the drum rotate slightly which cams the shoes into the inner surface of the drum)

 

[AMCRambler]

Originally posted by: Shanti
Is it hard to take drum brakes apart and clean them?

The back brakes on my van were squealing. I had them checked out because I thought they needed replaced. The guy said they were fine, he just had to clean them off. But now, a couple months later, they are making squealing and grinding noises again.

It's not that hard. Usually they have a couple of retainer bolts on the face after you pull the wheel off, take these out. Give a tug on the drum and see if it pulls off. If not then the drums are probably fairly worn, you may have to adjust the shoes away from the drum. There's usually some kind of wheel inside the backing plate you can turn with a screw driver to do this. That should loosen it up so you can pull the drum off. Sometimes they do get frozen on there pretty good and you need a puller tool to get them off. Haven't had this happen to me yet though. If it's stuck, usually a tap or two with a sledge on the edge of the drum in the direction it's supposed to come off will free it up. Piece of cake!

 

[Fatdog]

Originally posted by: Roger
Disc brakes have one failing, they require a lot more line pressure to activate compared to drum brakes which are self energizing.
(The shoes upon contact with the drum rotate slightly which cams the shoes into the inner surface of the drum)

And this is one of the biggest reasons you see drums on the big trucks (though I have seen a couple with discs on the front axle). The drums are an easier and cheaper system to maintain and use on big commercial trucks.

I will say this, when you do overheat them and they fade to nothing, it gets mighty exciting. :Q

 

[Bulk Beef]

I will say this, when you do overheat them and they fade to nothing, it gets mighty exciting.

I roadraced about half a season on a vintage two stroke with a massive 2LS drum on the front - THAT was exciting. What a POS!!

 

[boyRacer]

Originally posted by: sward666

I will say this, when you do overheat them and they fade to nothing, it gets mighty exciting.

I roadraced about half a season on a vintage two stroke with a massive 2LS drum on the front - THAT was exciting. What a POS!!

:Q lol...

The 550 Spyder has drum brakes all around... ... but i love that car... :heart:

 

[308nato]

Originally posted by: sward666

I will say this, when you do overheat them and they fade to nothing, it gets mighty exciting.

I roadraced about half a season on a vintage two stroke with a massive 2LS drum on the front - THAT was exciting. What a POS!!

H2's forever !!! Ah, roadracing when men were men and the equipment was...er...the highest tech available. Yvonn Duhamel was very brave man.

 

[Bulk Beef]

Originally posted by: 308nato

Originally posted by: sward666

I will say this, when you do overheat them and they fade to nothing, it gets mighty exciting.

I roadraced about half a season on a vintage two stroke with a massive 2LS drum on the front - THAT was exciting. What a POS!!

H2's forever !!! Ah, roadracing when men were men and the equipment was...er...the highest tech available. Yvonn Duhamel was very brave man.

A better man than I, that's for damn sure. Piston port two strokes are bad-ass. I will say that the bike was fast, and launching it was fun (pin the throttle to the stop and do all the modulation with the clutch), but trying to stop and get around a corner was absolutely terrifying.

 

[LAUST]

Just working on them alone Disk > Drum

 

[Demon-Xanth]

Heh, the only hard part about disk brakes is when they're part of the hub and you gotta disassemble the hub to get them turned. The pads are almost always easy though.

 

[C'DaleRider]

Thank goodness for discs.......nothing more exciting than driving a car with all drum brakes, driving through water and trying to stop. If you haven't had the pleasure of panic trying to quickly stop because you forgot to dry out your brake shoes after you went through that last puddle of water, find an old 60's car with drum brakes and have fun. I'll stick with discs.

 

[AMCRambler]

Originally posted by: C'DaleRider
Thank goodness for discs.......nothing more exciting than driving a car with all drum brakes, driving through water and trying to stop. If you haven't had the pleasure of panic trying to quickly stop because you forgot to dry out your brake shoes after you went through that last puddle of water, find an old 60's car with drum brakes and have fun. I'll stick with discs.

As the owner of a 66 Amc Rambler I'd have to agree.