Why do Brake Drums need to be turned?

[V6UnderPressure]

I sort of understand but maybe I dont. I know its to get the entire surface even but if the shoes are the same width on the car, why do they need to be turned? And how much does it cost and where can you get it done?

Scott

 

[zam70]

turning is done to smoth out the contact area. More area = better braking power and less heat generated.

If you take the drums off your self and take them in to get turned it is Cheap...8.00 a drum I think. Most any auto service place (who does brakes) can turn them.

 

[V6UnderPressure]

What if you swapped them right away from one car to the other. Would they still need smoothing?

Scott

 

[humberto]

To correct brake pulsation.

 

[equalizer442]

you turn the drums because the drums are warped, i can promise you right now that no one on this board has a car that dont need the drums or rotors turned. now some drums cant be machined but for the most part the drums will tell you there max diamater that you can turn it. once you hit the max diamater you should go and buy your self a new set of drums.

your suposed to have the drums and rotors turned every time you change your brake pads/shoes so the parts dont warp over the magic .003 of a inch, once that occures you will be able to feel the "wobble" when you apply the brakes.

most shops use a rough cut because it will get you in there quicker to buy more brake pads then a smooth cut. i personally will do a smooth cut on every drum/rotor i do and if i get told by the boss man to start doing rough cuts ill pack my tools and head out the door.