Brakes
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==Preamble== | ==Preamble== | ||
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This article will introduce you to brakes and the components that are involved as they apply to the automotive world. We will try to break down the brake system in to its proper categories so that you can understand them better and apply that knowledge. | This article will introduce you to brakes and the components that are involved as they apply to the automotive world. We will try to break down the brake system in to its proper categories so that you can understand them better and apply that knowledge. | ||
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In this article we will look at what ''is'' important in stopping a vehicle and what factors are involved. The reader should remember the concepts behind braking in this article. These concepts are universal: no matter what vehicle we talk of, improving stopping distance is a matter of applying physics based on vehicle parameters, driving habits and driving conditions. | In this article we will look at what ''is'' important in stopping a vehicle and what factors are involved. The reader should remember the concepts behind braking in this article. These concepts are universal: no matter what vehicle we talk of, improving stopping distance is a matter of applying physics based on vehicle parameters, driving habits and driving conditions. | ||
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==Caliper types== | ==Caliper types== | ||
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==Rotors== | ==Rotors== | ||
| + | Slotted and cross drilled rotors help cool the brake system with airflow across them and the calipers. Without sufficient airflow, having slotted or cross drilled brake rotors is hardly more effective than standard ventilated discs. The slotted/drilled rotors do help with brake pad out-gassing; when the pads reach their operating temps or higher they start to give off gas as they wear and the slots and/or holes gives this gas a place to go so it doesn't build up between the pad and rotor, causing a loss of brake effectiveness. | ||
| − | [[Image: | + | {| |
| + | |[[Image:Disc_vented.jpg|thumb|center|700px|Typical vented rotor]] | ||
| + | |[[Image:Slotted_vented.gif|thumb|center|500px|Slotted and vented rotor]] | ||
| + | |[[Image:Slotted_x_drilled.jpg|thumb|center|300px|Slotted and drilled rotors]] | ||
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| − | + | The downside to cross drilled rotors is reduce surface area, a decreased co-efficient of friction and they might be more prone to warping or cracking if not done correctly. | |
| − | + | The advent of carbon metallic friction materials with their increased temperature stability and friction coefficient characteristics can mean slotted/drilled rotors are needed less than before. Typically, in original equipment passenger car applications these holes are cast then finish machined to provide the best possible conditions to resist cracking in use. But they still may crack eventually under severe circumstances. With a properly designed brake system, drilled ventilated discs can operate cooler than non-drilled non-ventilated discs, due the higher airflow rates through the vents from the supplemental inlets and increased surface area of the holes. The airflow is into the hole and out through the vent to the OD of the disc. If discs are to be drilled, the external edges of the holes must be chamfered or radiused. | |
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==Drum brakes== | ==Drum brakes== | ||
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[[Image:Drum_brake.gif|frame|none|Internal drum brake illustration]] | [[Image:Drum_brake.gif|frame|none|Internal drum brake illustration]] | ||
| + | ==Brake system== | ||
The picture below shows a typical set of hot rod brakes which utilizes an adjustable proportioning valve, residual pressure valve, master cylinder, and brake booster. This is a system from an under-floor brake setup. | The picture below shows a typical set of hot rod brakes which utilizes an adjustable proportioning valve, residual pressure valve, master cylinder, and brake booster. This is a system from an under-floor brake setup. | ||
[[Image:Hot_rod_brake_system.jpg|border|450px]] | [[Image:Hot_rod_brake_system.jpg|border|450px]] | ||
| − | ==Proportioning valves== | + | ===Proportioning valves=== |
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An adjustable fluid valve that allows you to set the amount of pressure being applied to a wheel cylinder by increasing or decreasing the fluid by way of a adjusting valve. | An adjustable fluid valve that allows you to set the amount of pressure being applied to a wheel cylinder by increasing or decreasing the fluid by way of a adjusting valve. | ||
| − | ==Residual pressure | + | ===Residual pressure valves=== |
| + | A one-way valve that allows fluid to flow through it at any pressure, but limits the amount of return pressure to a certain amount by way of a spring loaded check-valve. Usually comes in 10 psi (red color) for drum brakes and 2-3 psi (blue color) for disc type brakes. These valves are mainly used in under-floor systems where the calipers are higher than the master cylinder reservoir and to compensate for the return spring tension in drum brake systems. RP valves eliminate excessive brake pedal travel in both systems | ||
| − | A | + | ===Master cylinders=== |
| + | A dual reservoir master cylinder (MC) is used in any modern vehicle and should be used on older vehicles that had single reservoir master cylinders. | ||
| − | + | Usually a drum brake master cylinder will not work for disc brakes because the bore size is too small, and the drum brake MC may have a built in residual valve. | |
| + | ====Power master cylinder diameter and pedal ratio==== | ||
| + | Most times, a master cylinder for a power brake system should have a pedal ratio of about 4:1 when using a master cylinder bore diameter of 1-1/8". | ||
| − | == | + | ====Manual master cylinder diameter and pedal ratio==== |
| + | Most times, a master cylinder for a manual brake system should have a pedal ratio of about 6:1 when using a master cylinder bore diameter of 1". As a rule of thumb, a pushrod attachment point on the brake pedal about 1" above where the power brake attachment point was (closer to the pivot point) will be about right for a manual brake system. | ||
| − | + | If using a bore larger than 1" on a manual system, the brake pedal effort can become very high. | |
| − | [[File: | + | [[File:Pedal ratio1.jpg|thumb|700px|left|Pedal ratio guidelines from mpbrakes.com]] <br style="clear:both"/> |
| + | ===Brake boosters=== | ||
| + | In most cases the vacuum required to operate a power brake vacuum booster should be at least 18" for best results. In most cases anything less than 14" of vacuum will not be enough. Using a vacuum reservoir is not a very good substitute for inadequate vacuum. In cases where there's not enough vacuum, a vacuum pump may be used, or the system changed to manual brakes. | ||
| − | ==Brake lines== | + | If space is a problem, a dual diaphragm booster might be enough smaller in diameter to help. |
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| + | ===Brake lines and fittings=== | ||
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| + | [[File:SM_brake_fitting01.jpg|border|300px]] | ||
==Resources== | ==Resources== | ||
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