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Brakes: Drum vs. Disc

Edmunds.comEdmunds.com Posts: 10,059
edited November 2014 in General
imageBrakes: Drum vs. Disc

Brakes: Drum vs. Disc article on Edmunds.com

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Comments

  • Here is a great video tutorial on how to replace drum brakes!
    www.ericthecarguy.com
    Replacing Drum Brake Shoes Part 1

    Replacing Drum Brake Shoes Part 2


    Enjoy.
    b.
  • voyager7voyager7 Posts: 1
    Disc vs Drum. okay- While true about cooling advantages of the disc brake there is a major drawback and design problem with the disc/ caliper design. The problem is constant rubbing of the brake pad against the rotor.

    I see this on all disc brakes. See for yourself. Remove the wheel and try to spin the rotor- it won't spin freely. Why? because the pads always touch the rotor causing friction and a constant braking effect. I expect this is worse when the pads heat up.

    On the other hand drum brakes do not have this rubbing problem because the shoes retract from the attached springs.

    I think the drum is better.


    Voyger7
  • tedediahtedediah Posts: 2
    Voyager: Was your car in park or was the e-brake on? Otherwise, did you have it in gear? Or, was opposite side wheel still touching the ground? All of those things would have made the wheels not spin freely.
  • Voyager: The piston retracts once the brake pedal is released. If such were true then you'd have to change brake pads very often. Maybe there was a problem with the brakes you were looking at or the reasons tedediah suggested.
  • geommmmgeommmm Posts: 1
    What this does not explain is why disc brakes are more effective than drum brakes even when they are both cold
  • geommmm - this is actually explained.

    Friction is an aspect that is fixed in both disc and drum brakes.
    Friction causes heat - overheating causes the drum brake to sometimes not work.
    Regardless of how cold it is, with friction, heat occurs.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    If the car were light enough, and didn't have tremendous horsepower, drum brakes would be perfectly adequate. The 1965 Corvair had drum brakes which were excellent, and comparable in performance to disk brakes. So the problem is that most modern cars and trucks are just too heavy for drum brakes anymore---you'd need gigantic finned drums to deal with the heat buildup. This was also true of most "classic" cars--they were conspicuously underbraked because of their weight.
  • Drum brakes don't get wet like disc brakes which causes braking loss.
    Disc brakes are not self energizing like drum brakes
    Disc brakes have much higher maintenance cost due to:
    1- Calipers can't be repaired as easy as wheel cylinders
    2- Rotors rust quickly
    3- Rotors warp
    Disc brakes harder on the environment due to high frequency of rotor and caliper replacement compared to drums
    Wheels are forever dirty with disc brakes
    Disc rotors and calipers are heavier than drums and wheel cylinders

    You can have your disc brakes.
  • thecardoc3thecardoc3 Posts: 5,091
    If what you wrote was really accurate, you wouldn't see disc brakes on just about everything that is made today. Even heavier trucks have disc brakes since they greatly out perform the older drum designs.
  • I am a full time automotive technician and rotors for the average sedan (even the ones that have the e-brake as a drum within the rotor) run about $20-$30 each from O'Reilly's - whereas the average drum for the common rear brake runs $40-$50. It is true that shoes are a little cheaper than pads and wheel cylinders are a little cheaper than calipers, but my average drum job is more expensive than my average rotor job, plus it takes me twice as long.

    I dont mean to disagree with thecardoc3, but every Semi Truck and trailer I have ever seen has massive drum brakes. The reason being that drum brakes do indeed have more stopping power (more surface area and more positive applying leverage) Heat, as stated before is the issue that common drivers do not understand or account for, whereas truckers understand (usually) how to apply their brakes intermittently to allow for cooling.

    It has always been my assumption that pitted against one another on vehicles of identical weight, that Drum brakes would bring the vehicle to a short quick stop from medium speed much faster than disks - but disks would maintain braking power over longer faster stops due to their ability to dissipate heat... I would like to see a test such as this done :)
  • steverstever Posts: 52,462
    edited October 2016
    My ideal is front discs and rear drums.

    (and welcome)
  • thecardoc3thecardoc3 Posts: 5,091
    edited October 2016
    Semi Tractor disc air brakes. http://www.foundationbrakes.com/en/products/airdiscbrakes/airdiscbrakes_1.jsp

    Here is a video. Those are some huge calipers, not even counting the diaphragm.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    edited October 2016
    Some drum brake cars offer outstanding braking---the '65 Corvair for instance. But heat dissipation? Not so much.

    Nonetheless, there were cars in Europe winning races at incredible speeds (even by today's standards) with drum brakes.
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