Disc Brakes Vs Drum Brakes

[GasSavers_maximilian]

Is it true the front wheels see more of the braking force? Is that why discs are used there? I've also heard people claim discs are less susceptible to clogging with debris as they can spin it out. Not sure about either claim.

[GasSavers_maximilian]

I heard a couple years ago about a new design that made an electric disc brake viable by taking advantage of the centrifugal force available in some manner. A quick Google search didn't pull it up and I'm fuzzy on the particulars.

[theholycow]

Front wheels see far more braking force, especially for people who brake hard.

http://www.auto-repair-help.com/auto...ning_valve.php

I doubt that discs are any more or less susceptible to clogging with debris. Drum brakes are enclosed, though rust and such could build up inside. Disc brakes are exposed but the pads are always almost rubbing the rotor so there's no room for significant debris to get in, and even if it does it's not lilkely to prevent the brake from stopping the car (though it might score the rotor).

[GasSavers_maximilian]

Originally Posted by theholycow

I doubt that discs are any more or less susceptible to clogging with debris. Drum brakes are enclosed, though rust and such could build up inside.

I think they did mean rust.

[GasSavers_NovaResource]

Originally Posted by maximilian

Is it true the front wheels see more of the braking force? Is that why discs are used there? I've also heard people claim discs are less susceptible to clogging with debris as they can spin it out. Not sure about either claim.

Front brakes do approximately 70% of the braking. That's not just during hard braking, that's under normal braking. Under hard braking, when the weight transfer moves forward, the front brakes can do even more work. Look at a typical 4-wheel disc car and you will notice the rotors and pads are larger on the front wheels than the rears. Also, front rotors are vented while rears are solid. Vented rotors cool faster but cost more, are thicker and are heavier.

Vented rotors:


Solid rotors:


Don't get me wrong about discs vs drums. With the use of power assist for brakes, discs are far better for a vehicle. While a drum brakes may work better when cold, the are quickly overheated and lose their effectiveness. Discs do a much better job of handling heat. Take an easy drive where you use the brakes very little. The rotors will still be hot enough to burn you when you stop. Even the wheel itself will be very hot to the touch.

Discs also shed water and brake dust easier. That's why cars with disc brakes have dirtier wheels. You will also notice the front wheels get dirtier faster than the rears. That's because the fronts do more braking work and because some cars still have rear drums that keep the brake dust inside the drum.

As for rust, discs rust faster because they braking surface is exposed to water while the draking surface on drums in inside the drums. However, the rust is quickly removed by the pads. This is why after a rain the brakes make funny sounds the first few times to use them.

[theclencher]

I say, it depends on how you drive.

As a flatlander that drives gently, my brakes scarcely get used at all. I have over 110,000m on the factory pads on my new vehicle. Over heating is not an issue. Power is not an issue. I would do better with 4 wheel drums. I have several classics with 4 wheel drums. I prefer them. I laugh at all these guys that, when building their rods, think they need front or four wheel discs. They are blindly following the crowd.

[GasSavers_NovaResource]

Just because you have a flat drive and brake easy doesn't mean everyone does. Most classic car and street rod guys drive hard and need disc brakes. Disc brakes are superior to drums in just about every aspect and that is why they are used today. The only places drums have an advantage is in cost, rotational weight and they make a better emergency/parking brake.

[Jay2TheRescue]

Disc brakes definately stop better. No question about that. If you're building a car that can go over 100 MPH you need to put brakes in that can stop a car going that fast in a reasonable distance. If you're re-doing an older car for performance and you don't upgrade the brakes I think you're crazy, unless the car is a trailer queen and really doesn't get driven much.

-Jay

[theclencher]

My drum brake cars can put you through the windshield.

Two of them can go over 100.

As pointed out, the main deficiency of drum vs disk is heat rejection.

If you don't do 10 hard stops in a row, there is no issue. If you only have to do a couple hard stops in quick succession, I don't see where drums have any deficiency. I've never been anywhere CLOSE to experiencing brake fade with the drum cars.

What hypermiler is on the brakes enough for that to be an issue? This is the econo forum right? Or should I have taken that left turn at Albuquerque?

What hot rodder drives hard enough to tax his brakes? Seriously. You aren't pulling the wool over my eyes. I've been in car clubs longer than some of you have been alive; I know 99.9% of "hot rod hardware" is for show.

The guys that actually do track events are the ones that realize the benefits of discs, but the street guys? Not so much. Edit: emphasized cuz I guess someone didn't see it the first time?

I'm not anti-disc. For high performance like motorcycles and snowmobiles, discs are way better. Trucks pulling/hauling heavy loads- eh, I don't know. Mine have drums in the back and the trailers have drums too. High performance cars should have discs too, I suppose, but I don't drive that hard on the street.

Whatever though. I know I'm not going to start any movement or hot trend for drum brake conversions! Just sayin', the "common knowledge" and the blanket statements of "disc brakes are better" have caveats.

If it wasn't so much work I'd put drums on the front of my Tempo. Clean rims, less drag.

[GasSavers_NovaResource]

Originally Posted by theclencher

You aren't pulling the wool over my eyes. I've been in car clubs longer than some of you have been alive

So have I so don't assume.

Originally Posted by theclencher

What hot rodder drives hard enough to tax his brakes? Seriously. I know 99.9% of "hot rod hardware" is for show.

Then you've been hanging around pussies, not hot rodders. Trailer queens aren't hot rods, they are nothing but automotive sculptures. Real Hot Rodders drive their cars and drive them hard because they enjoy the speed. I've had my Nova down the track hundreds of times (some legal, some not). I've driven cars with drums and cars with discs. Cars with power brakes and cars without. Disc brakes work better, period. Thinking a street car can't benefit from disc brakes is ludicrous. The benefits of drums over discs for fuel economy is too minimal to even measure but the benefits of discs over drums for safety is immeasurable.

Originally Posted by theclencher

If it wasn't so much work I'd put drums on the front of my Tempo. Clean rims, less drag.

See, that's my problem with most hardcore hypermilers. You are willing to do things that are unsafe just to get slightly better mileage. Tailgating trucks, taking turns at too high of a speed, turning off your engine while cruising etc. Changing from discs to drums is not only expensive but making your car less safe. Would you remove the airbags and seatbelts to make your car lighter in an effort to increased fuel economy?

I'm all for saving fuel but not at the cost of safety. Not just my safety but the safety of the other drivers on the road.