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(79 votes) Published: Oct 24, 2007 4:40 p.m. Viewed 222 times
UNDERSTANDING BRAKE PRINCIPLES A simple brake system for a car isnt as complex as most people think it is. The brake pedal is hooked up to a brake hydraulic master cylinder which is just a hydraulic pump. The master cylinder uses a reservoir that branches to 4 individual lines that each go to a wheel. The rear 2 lines are usually first intercepted by a proportioning valve that regulates the total brake pressure by percentage to the rear wheels. A lever connected to the rear axle controls a hydraulic pressure regulator which prevents the rear wheels from locking up over bumps. What this does is just close a valve in the brake line so that when the wheel is extended out (less weight on one wheel) the brake pressure drops so that braking around corners and over bumps wont cause a spinout. The line continues until it reaches a brake piston which is built as a caliper that pushes the brake pads (friction material, ceramic, kevlar, asbestos) against a brake rotor which is attached to the wheel and rotates as one with the wheel, axle, hub and transmission.
It is much like the brake system on a bike except instead of using a cable to compress or squeeze two objects (brake pads) toward eachother, it does it hydraulically.
Most cars have a brake booster system that uses vacuum created by the engine to give extra brake pressure so that there is less work for the operator. This is why the brakes can be pumped up and brake pressure will be high when the engine is shut off and its also why stopping a car using the brakes while coasting a car downhill with the engine off is pretty hard. The engine’s vacuum is very important to a car’s braking. While doing 45 mph, put your car in neutral and rev the motor to 6000 rpm while simultaneously slamming on the brakes. You will stop pretty quick. Try this with the engine at 900 rpm, youll stop alot slower. This is how mercedes, ferrari and volvo design performance brake systems that stop safer and quicker.
Drum brakes are considered inferior to disc brakes but last longer because there is little/no braking or friction surface exposed to water, dirt, and rocks. Drum brakes are generally used on the rear wheels of cars because the rear brakes require less stopping power and they wear out slower.
PERFORMANCE AND AFTERMARKET
There are many types of disc brakes and calipers. There are single piston calipers and multi-piston calipers which branch the brake line to each wheel into 2 or 3 lines which control pressure to multiple pistons on one disc.
For rotors, there are solid rotors, cross-drilled rotors, vented-rotors, vented-cross-drilled-rotors, drilled-rotors, vented-drilled-rotors, slotted rotors, slotted-vented-rotors, slotted-cross-drilled-rotors, slotted-drilled-rotors, slotted-vented-cross-drilled rotors and slotted-vented-drilled rotors. The most common rotors on economy and family cars on the market are solid rotors and vented rotors.
This is an entire drilled rotor package including drilled-vented-rotors, calipers, caliper brackets, anti-rattle clips, brake pads, stainless steel brake flex lines, gaskets and hardware. Notice as the brake rotors are drilled.
Here is a better diagram of cross-drilled-slotted-vented rotors.
What does this all mean and what does it do for performance? Before understanding why aftermarket brake setups are so good, you need to understand the downfalls of the stock brakes.
BRAKE FADE Friction fade: The friction material of a brake pad isnt generally a thermoplastic, instead it is a thermoresin. It will not melt because it is a ceramic or asbestos-based material, however it doesnt mean that it is resistant to heat. These materials are generally cured in the manufacturing process at 450+ degrees fahrenheit. Car brakes heat up significantly and can reach that temperature easily. When the pad reaches this temperature, its friction quality reduces drastically. The material cannot create friction with the brake rotor as easily so even more brake pressure is needed before the car can be slowed. If you want to experience this so you know what it feels like, take your car onto the highway and speed it up to 80 mph, hit the brakes and slow it down to 60, speed it back up to 80, and do this 3 times. When you turn off the highway within 30 seconds, you will notice that when you keep your foot at Ex. 1/2 brake pressure, the car will not slow down consistently.
Brake Fluid Boil: Dirty or old brake fluid has the tendency to boil up easier than new fluid. If you have an old shitbox car that is driven to the max and you dont follow its maintenance schedule, if you slam on the brakes from 45 mph after driving for awhile, you will notice that the brakes work better after you pump them up. This is because the fluid boils and lets out gases/air. What this does is it makes the brake pedal feel spongy and unresponsive and the air compresses within the brake line rather than letting the fluid push pressure. You will need a brake bleed if this happens.
Performance Brakes are different from Stock economy brakes because they are designed to create friction at any overkill temperature. They use brake pads that cool easily and work at temperatures up to 700 degrees F. The brake caliper has multiple pistons that push on the brake pad so that equal stopping force is applied on the pad. This prevents the pad from shifting and hitting the rotor at an angle such that it makes the brakes wear unevenly and squeak loudly. The rotors are designed to release dust and dirt away from the rotors easily and not collect it. Dirt and dust doesnt let the brakes cool down as easily and it can make uneven braking, difficult movement of the brake sliders (which the pads use to move on) and prevents the hot brake dust from caking onto the rotors, calipers and brackets which makes things dirty and makes things overheat and wear out easier and faster.
Drilled Rotors are designed so that they allow even brake rotor cooling and release of brake dust so that the braking always stays consistent and smooth. The only issue is that the constant heating and cooling of a solid piece of metal with holes in it can cause the metal to crack around the holes. This is because the metal can only expand and contract so much because it is limited as to how much the holes can stretch.
Cross-Drilled Rotors are designed to have all of the benefits of Drilled rotors but they allow more flexibility in the heating and cooling of the rotor. It also lets the entire pad surface cool down even more because holes are drilled in a way that allows the entire pad to get cooling once an entire wheel revolution is made
Slotted Rotors are made so that the entire brake pad surface can be exposed to the air to cool down in less than 1/12th of a wheel turn. This means that the brake pad will release brake dust and cool down 12 times every time the wheel spins. This has a great performance advantage over any drilled rotors when combined with vented rotors but has a shorter rotor life because the slotting only covers up 2% of the brake surface and once 2 pad sets have worn into the rotor, there isnt much slotting left on the rotor. Drilled rotors will remain drilled the whole way through the rotor.
Vented rotors are common in heavy vehicles that need alot of brake cooling and venthilation. It basically just releases heat and gases produced by the friction material burning off and allows release of brake dust. Rather than releasing the brake dust on the surface of the rotor, it gets sucked towards the hub through some vents and gets tossed out through the middle of the rotor halfway in the offset.
VENTED ROTORS:
DRILLED ROTORS:
DIAMOND SLOTTED ROTORS:
CROSS-DRILLED ROTORS:
VENTED SLOTTED DRILLED ROTORS:
2 PISTON BRAKE CALIPER:
So i was driving my mom’s car down the street and the speed limit is 30 mph. I was doing 140. There were some school children, a few nuns holding kittens, 4 old ladies working for different charities, some orphans and a parade of elderly war veterans in wheelchairs crossing the street. So i looked up and saw that i had a red light. Thats when i saw the sign on the dashboard.
Oct 25, 2007 2:51 pm - meh gauges are overrated. This reminds me, i actually need to replace the brakes on my car. I also need to replace my right axle which i snapped this morning on my way to school. I did a huge burnout and ran over a rock and snapped my damn axle.
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