Disc Brakes Vs Drum Brakes

..so according to this logic all the cars with disc brakes should crash when it is raining.Water affects both dics and drum brakes, most modern disc brakes have a 'cleaner' function which wipes the brakes dry(this is automated with ABS equipped cars).Water becomes an issue in case of submersion and not during regular use and disc brakes are far better than drums in any condition.
Ceramic brakes are exotic item seen in supercars (porsche/SLR..etc) and cost the equivalent of a small family car!!(4 lacs)..they work at high temperatures and are not very good for city driving.Even better are carbon brakes and carbon ceramic hybrid brakes.

Hi,

It is a myth that disc brakes are better in performance than drum brakes...but, in one aspect, disc brakes are certianly better than drum brakes.

Why because, the design of a disc brake allows for heat dissipation. The open to atmosphere design allows the heat generated due to braking to be quickly dissipated to the atmospere. The heat therefore cannot affect the long term life of the disc brakes. Drum brakes, due to their enclosed design take a longer time to release all the heat that is generated during braking. This might explain why drum brake linings wear quite often and that lining wear is also influenced by the driving habits of the user!

Why do you need disc brakes for the front wheels usually? It is because of 'weight transfer'...just think why do you tend to lean forward in your bus seat, when the driver applies brake? It is because weight transfer takes place from rear to the front of the vehicle during braking. So, the braking torque on the front wheels is higher which means more heat generation in the front brakes. So, it is essential that this heat is let out as early as possible.

Performance wise, the drum brake as well as the disc brake do the same function relative to the required braking torque on the rear and front wheels respectively.

Just imagine, is it safe enough to have brakes in the front performing better than those in the rear?? You just cannot compromise on 2 things in an automobile...they are the steering system and the braking system

Nice discussion.  Please have a look at this article/link. Thanks.

I lost the discussion after this point- could you elaborate how the drums have equivalent performance to the disc brakes.

Hey Karan,
 I understand what you mean. The newer cars have greater brake pressure. This is done to increase the comfort of the driver. The way power steering started for easier turning. But these aren't power brakes, but just an increment of pressure. And talking about the brakes getting hard, well the master cylinder is hydraulic and requires power hence when the car is switched off, the hydraulic system too turns off. Hence, its harder. Exactly like the power steering, just try inserting the key and turn the steering and now switch on the car and just try steering.



Our Passion Is our Strength.

 

I guess it has to do with the basic physical process that takes place while braking: Motion (kinetic energy) is converted to heat by the brake pad/shoe. So disc & drum brakes in that sense do the same thing - use friction to convert the rotation of the wheels to heat which is dissipated.

 

Is it? Please elaborate.

Our Passion Is our Strength.

 

thanks Rohit -but my post was cynical on what the poster had posted about disc brakes and drum brakes performing equally.(more of a jibe)

 

-the 'concepts' i guess i understand quite well!!

BTW, are modern braking systems fail-safe? Apart from using the hand-brake, can a driver do anything at all if the main brake pump or hydraulics fail?

-modern brake systems are almost 100% faile safe. Moreover the brake lines are diagonally connected-so even if two wheel brakes fail the other two will help in stopping the car.

 

-in the event of complete failure-shift down to a lower gear-reduced speed- and then switch off the engine(and pray)