http://www.edmunds.com/ownership/techcenter/articles/43857/article.html
เท่าที่อ่านจากที่นี่ ผมเข้าใจว่าถ้าไม่ได้ขับเร็ว หรือไม่ได้เอาไปขึ้นเขาลงห้วยก็ไม่เป็นไร
ถ้าจำเป็นต้องเบรคกระทันหัน drum จะสู้ disc ไม่ได้ แต่มันก็แค่เสี้ยววินาทีคงไม่เป็นไรหรอกครับ
อีกอย่างคนซื้อมาสด้าคงไม่ได้เอามาขับ Zoom Zoom กันทุกคนอยู่แล้ว
แล้วก็เข้าใจว่าถ้าใช้ engine brake ไม่ได้ใช้ drum หลังก็น่ากลัวอยู่ครับ รุ่น 1.6s manual คงไม่เป็นไร แต่ auto นี่....
One of the first steps taken to improve braking came in the early '70s when manufacturers, on a widespread scale, switched from drum to disc brakes. Since the majority of a vehicle's stopping power is contained in the front wheels, only the front brakes were upgraded to disc during much of this period. Since then, many manufacturers have adopted four-wheel disc brakes on their high-end and performance models as well as their low-line economy cars. Occasionally, however, as in the case of the 1999 Mazda Protege's, a manufacturer will revert from a previous four-wheel disc setup to drum brakes for the rear of the car in order to cut both production costs and purchase price.
Disc brakes
unlike drum brakes, which allow heat to build up inside the drum during heavy braking, the rotor used in disc brakes is fully exposed to outside air. This exposure works to constantly cool the rotor, greatly reducing its tendency to overheat or cause fading. Not surprisingly, it was under racing circumstances that the weaknesses of drum brakes and the strengths of disc brakes were first illustrated. Racers with disc brake systems could carry their speed "deeper" into a corner and apply greater braking force at the last possible second without overheating the components. Eventually, as with so many other automotive advances, this technology filtered down to the cars driven by everyday people on public roads.
Drum brakes
Under high braking conditions, like descending a steep hill with a heavy load or repeated high-speed slow downs, drum brakes would often fade and lose effectiveness. Usually this fading was the result of too much heat build-up within the drum. Remember that the principle of braking involves turning kinetic energy (wheel movement) into thermal energy (heat). For this reason, drum brakes can only operate as long as they can absorb the heat generated by slowing a vehicle's wheels. Once the brake components themselves become saturated with heat, they lose the ability to halt a vehicle, which can be somewhat disconcerting to the vehicle's operator.
Drum vs. Disc: Today
In today's automotive pantheon, it's not uncommon to find four-wheel disc brakes as standard equipment on medium-priced, non performance-oriented models. The majority of new vehicles, however, continue to utilize a front-disc/rear-drum brake setup. What does this say about the current state of braking systems? Are these manufacturers sacrificing vehicle safety in order to save a few bucks by installing disc brakes on only the front wheels?
http://www.ihpva.org/pipermail/trikes/2000q4/005764.html
- disk brakes are less prone to losing braking power due to water. I
used to have a 1962 Plymouth with drum brakes that was so bad it
seemed if you ran through even a small puddle, water would get into
the brake shoes and it would take 15-30 seconds of hard braking
before enough heat built up to boil out the water and actually
provide some braking power. It was terrifying, kind of like trying
to stop a bike with steel rims in the rain. Ironic in that disks get
more water on them, but with drums it seems to hide inside the drum
and won't drain out by itself;
http://www.ultimatecarpage.com/forum/showthread.php?t=8142&page=4
Quote:
Originally Posted by Blue Supra
what is brake fade in drums? ive heard it refer to and i have a slight inkling but im not sure.
It's exactly the same as for disks.
the firction material heats up beyond it's operating range and loses it's friction properties.
As drums are a LOT harder to cool than discs this is a bigger issue with drums. ( Hence why truck drivers will ALWAYS brake using the gears and engine as much as possible )
This has become a more sever problem with the loss of asbestos as friction material as metal sintered material isn't all that clever in drums. I saw an early set of metal sintered shoes STUCK to the drums as they had overheating so much that a layer of metal was melted onto the drum interior and stuck to the metal still in the shoes. Another one of the reasons for NEVER putting on the parkign brake when doign track days ( the main one is the brake can stop working as it cools )
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