By Scott Barton
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Introduction
So you want more braking power. While those Big Brake Kits may seem very attractive (until you look at the price), they are usually unnecessary and can sometimes even hurt braking performance if not designed properly for your car. While the front brakes do most of the braking, the rears must be used as much as possible to maximize braking performance. You want to have the ability to lock up both sets of tires at roughly the same time, with the fronts locking up just before the rears. This uses the maximum traction available of all four tires to help stop the car. By upgrading just the fronts to bigger/better brakes and not the rears, you have increased the fronts braking ability while leaving the rears the same. This effectively reduces the rears overall contribution in helping to stop the car. You are using the front tires maximum traction, but not the rear tires. Since the rear tires are now contributing less to stopping the car, you have actually just lost stopping performance and increased your stopping distance. What you will get with bigger front brakes is an increase in resistance to brake fade from repeated stops from high speeds. Oh, and they look nice. If you really want to upgrade to a big brake kit though, make sure it includes improved rear brakes as well, and that the entire system was designed specifically for your car. You can get almost as much performance as a big brake kit by just upgrading your stock brake system. It will cost you significantly less and it will be easier to install. By getting new high quality rotors, high performance brake pads, stainless steel brake lines, and high performance DOT 4 brake fluid, you can easily, yet significantly, upgrade your brake system without breaking the bank. Rotors Most people upgrading their brakes usually want to get cross-drilled or slotted rotors (or both). While these certainly look nice, they can actually increase the chances of rotor failure and may not even increase your braking performance.
The main reason for using cross-drilled rotors is that in the old days when you use your brake pads,
they would create gas (or out-gas, as it is called). This gas could actually create a cushion between
the pad and rotor. The cross drilled holes allowed the gases a place to escape from between the pad
and rotor. However, because of advances in brake pad technology, almost all newer pads these days do
not off-gas like those of several years ago. Another possible advantage to cross-drilled rotors is that
they may help cool the rotors by providing more surface area to be cooled by air.
These benefits may be offset, however, by reducing the amount of mass to be used as a heat sink,
since metal has been removed where the holes are now located. The reduction of surface area that
actually comes in contact with the brake pad may also become significant.
Slotted rotors have grooves cut into them. These grooves are used to cut into the brake pad so that there is always fresh pad on the rotor. This helps keep the pads from having a glazed surface that would reduce braking performance. Slotted rotors will significantly reduce pad life and increase brake dust, however. They also have adverse effects of slightly reducing mass to be used as a heat sink and a reduced rotor area that comes into contact with the pads. As you can see, slotted and cross-drilled rotors have their pros and cons. However, their biggest problem actually lies in how they were manufactured. If the rotors were drilled or slotted after they were cast, it will greatly increase the chances of rotor failure. By reducing the mass of the original design, it increases the rotor's susceptibility to warping. If cross-drilled rotors are designed improperly or drilled after they were cast, this will significantly increase their susceptibility to cracking. This can cause a catastrophic rotor failure and is very dangerous. If you decide that you want drilled or slotted rotors, it is important that you get a set of high quality ones that have the slots and holes cast into them. Stay away from the ones that were drilled or slotted after they were cast. Almost all cross-drilled or slotted rotors offered for sale for the average car were done after the casting. It is also important that the pattern of holes and slots must have been designed so that it does not affect the integrity or strength of the rotor. Drilled or slotted rotors are usually around $25 more than regular rotors. Vented rotors are better than solid rotors in their ability to cool. Vented rotors have vanes that allow air to flow through the rotor and provide more surface area to better dissipate heat. Rotors with curved vanes (left and right side specific) will flow air through them better than straight-vaned rotors. Two-piece rotors reduce weight, thus giving the benefits of less un-sprung weight and rotational mass, without reducing the mass of the heat sink or the surface area that comes in contact with the pad. BMW M3 Euro floating rotors are a perfect example of two piece vented rotors with curved vanes.
It is recommended to get the rotors plated. Plating prevents the rotors from rusting.
For the serious enthusiast who would like to get the most out of their rotors, cryogenically treating the
rotors will improve their performance and life span.
My suggestion would be to just to get a set of high quality non-drilled, non-slotted, plated rotors from a reputable manufacturer. If you can get ones for your application with curved vanes or two piece rotors, that would be ideal. If you feel you need it and can afford it, get them cryogenically treated. Brembo is one of the many manufactures that has high quality rotors for most cars. Most quality rotors cost anywhere from $35-$150 each. Brake Pads You can significantly increase your braking performance just by upgrading to high performance brake pads. It is important to find out the operating temperature and the coefficient of friction of the brake pad. A pad with a low minimum operating temperature will require little, to no, warm up before they work well, while a pad with a relatively high minimum temperature will require some time to warm up before they become effective. Pads with a high minimum operating temperature could be dangerous on the street and may not even get up to ideal temperatures during an autocross session. A pad with a high maximum operating temperature will be very resistant to brake fade, while a pad with a low maximum temperature will be more susceptible to fade. It is ideal to find a pad with a wide operating temperature range suited to your driving conditions and braking needs. The coefficient of friction determines how much "bite" a pad has. If there is too little bite, it will take a lot of effort to slow the car down. If there is too much "bite" it may grab too early and be hard to modulate. A medium to medium-high coefficient of friction is usually the best for street/track use.
High performance brake pads may increase brake dust, noise, rotor wear, and/or decrease pad life. While some pads
may experience some of these bad characteristics, not all do, and some may even reduce these problems compared to stock.
Some good pad manufacturers are Porterfield, Hawk, Carbotech, Axxis/PBR, Pagid, EBC, and Performance Friction (see Table 1). High performance pads can run from $35-$140 a set. Stainless Steel Lines Stainless steel brake lines help improve pedal feel and reduce brake fade. Rubber hoses can expand when they are hot and can deteriorate over time. This will make the brake pedal feel soft and mushy. Stainless steel lines do not experience these problems. Stainless steel lines can collect dust and dirt in the steel mesh, though. Over time this can rub a hole in the line and cause line failure. Plastic/teflon coated lines help prevent this problem. It is also important to get DOT rated lines. DOT lines have been tested to meet or exceed the DOT minimum regulations, and are required for street use. Goodridge and Stop-Tech makes some high quality SS lines for most cars. SS lines usually run between $75-$150 for all 4 corners. When replacing the lines, make sure to use flare nut wrenches to prevent stripping the nuts. DOT 4 Brake Fluid The main difference between DOT 3, 4, and 5 is the minimum wet and dry boiling points. DOT 3 specifies a minumum dry boiling point of 401°F and a minumum wet boiling point of 284°F. DOT 4 specifies a minumum dry boiling point of 446°F and a minumum wet boiling point of 311°F. DOT 5 specifies a minumum dry boiling point of 500°F and a minumum wet boiling point of 346°F. The higher the boiling point, the more heat the fluid can withstand before boiling. Boiling brake fluid results in a spongy pedal and decreased braking pressure. Stock brake fluid is usually DOT 3. DOT 4, which is compatible with DOT 3, is generally recommended. DOT 5 should not be used because it is silicone based and therefore not compatible with systems designed to use DOT 3 or 4 fluid. The dry boiling point is the point at which the fluid will boil when it is brand new and has not absorbed any water or moisture. The wet boiling point is the point at which the fluid will boil after it has absorbed water. Brake fluid is actually designed to absorb water. If it did not absorb and dissolve the water into the fluid, water pockets would be created. These water pockets would boil at a much lower temperature (273°F) and create brake fade. Water pockets could also rust the brake lines, which would be expensive to repair. Because brake fluid easily absorbs water, unless you change your fluid very often (every few months), the wet boiling point is the more important number to take into consideration since after a short time, the fluid will have water absorbed into it.
The most popular performance brake fluids are Valvoline Synthetic, ATE SuperBlue, ATE Typ 200, Motul RBF 600, and
Castrol SRF (see Table 2).
ATE SuperBlue and ATE Typ 200 (same as SuperBlue but without the blue dye) has a dry boiling point of 536°F, a wet boiling point of 392°F and costs around $12 a liter. It is good for serious autocross and some track use. Switching from SuperBlue to Typ 200 when changing the fluid makes it very easy to tell when all of the old fluid has been flushed out of the system due to the color difference. One thing to note is that the blue dye in SuperBlue can permanently dye the master cylinder if left in there too long. This would make it difficult to read the fluid level. Motul RBF 600 has a dry boiling point of 593°F and a wet boiling point of 421°F at a cost of $24 liter. It is more than adequate for autocrossing and good for track use. It should be noted that it needs to be changed more often. Castrol SRF Racing Brake Fluid is the ultimate brake fluid. It has a dry boiling point of 590°F, and an incredible wet boiling point of 518°F. At a cost of $64 a liter, it is only recommended for the serious racer with deep pockets. It also needs to be changed very often. Brake fluid should be stored in air tight sealed containers (preferably metal, not plastic) to prevent the fluid from absorbing moisture from the air. This is why it is best to use a new unopened can when filling the system. Because the brake fluid in the lines will absorb water over time, and its performance will also degrade after high temperature use, it is recommended to change the brake fluid at least every two years, but preferably sooner. For frequent track use it, is recommended that the fluid be no more than three months old. If you ever boil the fluid or experience excessive brake fade, you should change the fluid no matter how old it is.
You should be able to flush and fill the system with 1 liter of brake fluid if you are careful. I personally use
1 liter of Valvoline DOT 4 to flush and 1 liter of ATE Typ 200 or Motul RBF 600 to fill.
Related Brake Items SpeedBleeders from SpeedBleeder.com are a great way to reduce the chances of getting air into the system. They replace the stock bleeder valves with a one way valve that prevents air from going back into the valve when bleeding the system. They only cost $7 each and can come in shiny polished stainless steel for a few bucks more. SpeedBleeders are highly recommended, especially when you are already replacing the brake lines or changing the fluid. A MityVac vacuum pump is a vacuum/pressure pump that allows you to test all sorts of automotive systems. It is also a great tool that allows one person to easily bleed the brakes on any type of car. You attach a hose to the bleeder valve and use the vacuum pump to suck out the old fluid which prevents any air from getting into the system. Another product that makes bleeding the brakes easier is the Motive Power Bleeder from MotiveProducts.com. The Power Bleeder is a pressure brake bleeder similar to the professional tool mechanics use to bleed brakes. The Power Bleeder not only makes bleeding the brakes with one person possible, but also makes bleeding brakes easy. Another way to increase the performance of the brakes is to duct air to the brakes. It is most effective when the air is ducted to the inside of the rotor where it will flow through the vanes. There are some aftermarket brake duct kits out there for a few cars, however the average Do-It-Yourselfer could probably make their own custom brake ducts fairly easily and cheaply depending on the layout of your car. Cooling the brakes will go a long way in reducing fade due to overheating. The reduced temperatures will also increase the lifespan of your braking components. Alternate Option to Big Brake Kits Sometimes it is possible to retrofit slightly larger or better brakes from a different model car onto your own car. This can usually be done with little or no fabrication at all. If the upgraded front brakes are significantly bigger/better than stock, then it is advisable to upgrade the rears as well. Sometimes you can just use a brake-bias adjuster to give the rear brakes a little more stopping power without having to totally upgrade them. Make sure that your master cylinder can be used with this new system. If not you may also have to upgrade your master cylinder. Bedding-In New Brake Pads and Rotors It is important that you bed in new brake pads and rotors properly. You can break in new pads with old rotors, but you cannot break in new rotors with old pads. If you replace the rotors but use old pads, the pads will never properly mate with the rotors. When just replacing pads, you should turn the old rotors if possible. Basically, the proper bed-in procedure is to gradually heat up the pads and rotors to above operating temps over several braking attempts, but not to over do it. Then let them cool down completely for several hours. Here is the procedure recommended by Zeckhausen Racing:
Conclusion
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