Brake technology, just like suspension technology and fuel-system technology, has come a long way in recent years. What began in the '60s as a serious attempt to provide adequate braking for performance cars has ended in an industry where brakes range from supremely adequate to downright phenomenal. The introduction of components like carbon fiber, sintered metal and lightweight steel, along with the adoption of ABS, have all contributed to reduced stopping distances and generally safer vehicles (though ABS continues to provide controversy).
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.
Why are disc brakes better than drum and how much, if any, loss of braking occurs when using rear drum brakes on a modern car? That's what we're going to find out in this edition of Tech Center.
Friction and Heat
Before you can appreciate the difference between drum and disc brakes, you have to understand the common principles that both systems use when stopping a car: friction and heat. By applying resistance, or friction, to a turning wheel, a vehicle's brakes cause the wheel to slow down and eventually stop, creating heat as a byproduct. The rate at which a wheel can be slowed depends on several factors including vehicle weight, braking force and total braking surface area. It also depends heavily on how well a brake system converts wheel movement into heat (by way of friction) and, subsequently, how quickly this heat is removed from the brake components. This is where the difference between drum brakes and disc brakes becomes pronounced.
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.
Why are disc brakes better than drum and how much, if any, loss of braking occurs when using rear drum brakes on a modern car? That's what we're going to find out in this edition of Tech Center.
Friction and Heat
Before you can appreciate the difference between drum and disc brakes, you have to understand the common principles that both systems use when stopping a car: friction and heat. By applying resistance, or friction, to a turning wheel, a vehicle's brakes cause the wheel to slow down and eventually stop, creating heat as a byproduct. The rate at which a wheel can be slowed depends on several factors including vehicle weight, braking force and total braking surface area. It also depends heavily on how well a brake system converts wheel movement into heat (by way of friction) and, subsequently, how quickly this heat is removed from the brake components. This is where the difference between drum brakes and disc brakes becomes pronounced.