Track Series 2: Brake Lines & Fluids

The way hydraulic brakes work is very simple: through the medium of an incompressible fluid which we call the brake fluid, forces exerted at one point inside a closed system are transferred to another point in the system. One reason why most brake systems are hydraulic is because of the relatively immediate reaction in force when you apply your feet onto the brake pedal. On top of that, usually, the initial force that is applied to the brake pedal is multiplied within the hydraulic system, resulting in a higher force that is applied to the brake pads. Therefore less effort is needed by the user for braking. Since we have a more clear picture of what a hydraulic brake system does, let’s go a bit deeper into the specifics of the system in terms of brake lines and fluid that are used. 

Brake Lines

One component of the braking system that people often forget to upgrade before showing up at the track is the hydraulic brake lines. You might think that you would not gain much braking performance if you stick to the stock brake lines for track use, but as a matter of fact, having a solid set of brake lines would be detrimental to the overall effectiveness of your braking system. Standard brake lines that appear on stock vehicles are mostly made up of rubber which are sometimes surrounded by a fabric mesh for some extra protection. The downside of brake hoses such as this, especially at prolonged extreme conditions, is their potential to swell up within the system due to the immense heat. As rubber is naturally very flexible and stretchy when heated, the build up of hydraulic pressure in the lines under braking can cause the walls of the brake line to expand which results in a less effective braking force. To mitigate this effect, the walls of the brake hoses need to be made up of a much stronger and rigid material that can withstand the heat. As such, it is best to invest some money into a strong and durable set of brake lines such as a steel braided set.

Steel braided brake lines such as the HEL BMW F80 F82 Stainless Steel Braided Brake Lines provide a robust and long-lasting solution for hydraulic braking systems by reducing the swelling issue that is most commonly associated with the standard OEM rubber brake lines. Braided brake lines consist of a Teflon inner hose shrouded in stainless steel braiding for maximum strength and protection. In the extreme environment of a track session, these brake lines provide the necessary strength to transfer the hydraulic pressure input from the front brake pedal to the pads instantaneously. This allows the driver more control by braking quicker and harder at the critical tight corners resulting in potentially faster times!

Apart from that, the braided lines provide necessary protection to the system compared to rubber lines. One aspect of OEM rubber brake lines is that they are very easy to tear as well as the structural strength may deteriorate over time. This can cause braking fluid leakage. You wouldn’t want to lose braking ability from a puncture in the system when you are going at incredibly high speeds, do you? Therefore the braided lines reduce the risk of ruptures within your braking system while you are driving.

According to Instagram user, @mattbinsteadracing, he mentions that braided brake lines are a must as they are less likely to swell and flex with the extra heat generated on a track day. They will provide a firmer pedal throughout the heat cycles. Braided brake lines will give you more confidence with your brake system and provide repeatable and reliable pedal pressure that will have a much lower chance of splitting or breaking under the extra pressure, heat and forces generated.

📷: @m4_heritage_girl from Instagram

Brake Fluid

Now that you have strong brake lines, you must now consider what hydraulic brake fluid to use within the system. You might be tempted to use any old brake fluid, but not all fluids are made the same.

One consideration you must make when choosing the type of fluid to use on track is its properties of dealing with heat absorption. The brake fluid that is used on daily driven cars are rated for much lower operating temperatures and thus will not be suitable for extensive racing applications. As you use the brakes more often and much harder in track conditions, heat from the rotors and pads start to accumulate within the hydraulic system over time. When this happens you will notice that your braking force gradually decreases and at a certain point you will lose braking altogether. This is known as brake fade and clearly should be avoided at all costs. The way brake fluids are rated is based on its wet and dry boiling temperature as well as the DOT specifications. As a rule of thumb for racing applications, you should look out for DOT 4 or higher as they have a higher wet and dry boiling point as compared to standard DOT 3 fluids.

Therefore it is highly recommended that you opt for racing brake fluids with a high boiling point such as fluids that are rated at DOT 4 specification or higher to mitigate the effects of brake fade. A good example of a high-performance brake fluid that we recommend is the Castrol 1L React SRF Racing Brake Fluid which has a rated wet boiling point of 270°C, and a dry boiling point of 310°C. For track use, it is often recommended that the brake fluid is services often for optimum braking performance.

Final Thoughts

As you can tell, there are many factors that you need to consider when looking at upgrading your braking system especially when it is related to hydraulics. To ensure that your vehicle stops reliably and repeatedly when needed, attention should be given to these hydraulic components as your life will literally depend on them, so please do not treat them lightly.

Please look out for Part 1 of this article which elaborates on the brake discs and pads for use on track days.