Many think that if you want better stopping power you need massive brake rotors and 4+ piston calipers. Besides the enormous cost to many of these big brake kits, I see a couple of caveats that may be overlooked.
First, look at the number of production cars that have factory Brembo or other large calipers that simply can not hold up to more than a handful of laps on the track. Let’s name a few. The 350Z, Evolution, G35, BMW 1M, Mustang GT, Camaro SS, STi. They all need a little something more for the brakes to hold up lap after lap.
Another thing to note with most big brake kits is the additional weight. Aluminum calipers may weigh less than single piston cast calipers but have you held up a 355mm rotor? Those large rotors weighs a lot more than a factory rotor and that’s addition weight where you really don’t want it – spinning. In the end a big brake kit could potentially add 20 pounds of rotational mass. Of course you could always invest in a nice set of forged wheels to offset the additional rotational mass added by the brake rotors. Because RACECAR?
I’ve laid out several common complaints when it comes to braking performance. Identify the real reason your brakes aren’t cutting it and and save those hard earned dollars.
Spongy or Mushy Brake Pedal
When you press the brake pedal you are actually pushing hydraulic fluid through a hose that in turn pushes against pistons in your brake calipers. As brake fluid ages it becomes more prone to absorbing moisture. This changes the fluid’s compression mechanics and results in a mushy feeling brake pedal, or worse, a brake pedal that goes all the way to the floor.
Solutions
- Replace the brake fluid. In the automotive performance world, Motul600 and ATE SuperBlue are popular choices that take well to high temperatures where condensation may be absorbed in to the brake lines.
- Install Stainless Brake Lines. If you are certain that your brake fluid is good, consider replacing the factory rubber brake lines with stainless steel brake lines. The stainless steel wrapping will prevent the rubber from expanding when the fluid is compressed. If your brake lines are bubbling like a balloon then they need to be replaced before a catastrophe occurs.
Brake Fade
A couple laps at the track and the brakes don’t feel like they are biting? If the brake pedal is still firm then you likely have overheated the rotors or pads. Brake pads that come on most vehicles are designed for longevity. The pads bite well at lower braking temperatures observed during everyday commuting but do not fare well when subjected to higher heat ranges. The job of the brake rotor is more than simply providing a surface for the rotors to grip. Rotors promote heat transfer from the pad to the cooler material of the rotor. Thermal dynamics say that if the rotor gets too hot the heat from the pad will no longer transfer. An extremely hot rotor is also more prone to warping and causing vibrations. So to help keep the rotor cool manufactures create hollow veins allowing air to flow through the internal passages. Rotors which overheat may show signed of hairline fractures, cracking or worse, fall apart at speed destroying much more than your brakes.
Solutions
- Cooling ducts: Add ducts to channel cool air to your brake rotors. This is a remedy that can be found on just about any race car world wide. Even cars with large rotor and fancy calipers such as Alcon or Brembo still require additional cooling when subjected to race conditions. It is also cost effective.
- Different pads: Upgrade the pads to a compound which is rated at a higher temperature. The caveat to this is that performance pads may introduce squeal when braking at slow speeds or when cold. These pads often produce more brake dust meaning your wheels won’t stay shiny as long as they would with factory pads.
- Different rotors: Upgrade the rotors. This does not necessarily mean increasing the size. Brake rotors are available with various faced surfaces. Solid faced rotors are most common while slotted or drilled or a combination provide additional cooling capabilities at the expense of not being able to be resurfaced. Aftermarket rotors may have larger or different shaped veins which enhance cooling characteristics. Rotors may be offered in 2 pieces rather than 1 solid to reduce weight. Rotors may come in different materials that have better heat transfer and cooling properties.
- Go big: If solutions 1 through 3 don’t resolve brake fade then it may be time to look into larger rotors and calipers. Larger rotors provide more surface area and can absorb more heat. Calipers such as Alcon and Brembo allow for larger sized pads with greater surface area. Additionally calipers such as these generally make changing pads a breeze as pads are held in place with locking pins so the pads can be easily pulled out from the top.
Vibration Under Braking
If your steering wheel shudders and vibrates under braking its likely that the rotors have warped. Rotors are prone to warping after hard usage. To prevent warping its recommended to drive the car for several minutes without using the brakes to allow the rotors to cool. Also avoid using the parking brake or applying brake pressure when the car is stopped if possible.
Solutions
- Replace the rotors. Its possible that rotors can get out of round, and wobble. Replacing them if that’s the case is the only repair.
- Check the wheel bearings. When wheel bearings go out, the entire assemble wobbles and can give the illusion of a warped rotor. Have it checked out by your mechanic or read how to test.
Uneven Pad Wear
Unevenly worn brake pads are common with brake systems that use floating calipers. A caliper’s piston applies pressure from one side in order to squeeze the two pads together against the rotor. The caliper slides, essentially on a rail, to compress the outside pad. The floating caliper allows for slight amounts of lateral movement on the rail which equates to uneven pad pressure against the rotor.
Solutions
- Aftermarket caliper guides: These are often made of brass and are inserted into the caliper mount. These are guides, or sleeves, that minimize play to keep the calipers aligned while the caliper piston pushes against the pad. These are popular for the BMW 3 series.
- Change to a fixed caliper: A fixed caliper doesn’t slide on a caliper mount like a floating caliper does. This means the caliper never moves. The pads are squeezed evenly from both sides, theoretically equalizing pad wear. An upgrade to a fixed caliper solution can be put together using calipers from other vehicles. On the E46 M3, use of Brembo calipers from the 996 911 in conjunction with the CSL rotors is a popular budget upgrade. Alternatively, you could source an entire kit, thoughtfully crafted and put together from a reputable company such as AP Racing (check them out on our 2012 328i), Alcon, Brembo, StopTech, Rotora, and lastly but not least, Wilwood to name a few.
