Speed & Sound: Performance – Battle of the Buldge
Story by Budd Stanley
I was driving one of my favourite winding roads through the mountains the other day, when I noticed that my brake pedal was starting to feel soft heading down the steep declines. This required me to slow down, and conserve braking to cool down the discs, as well as the brake fluid that actuates the calipers. A bit annoying this was; however, on a track, this would be downright infuriating as valuable time is lost by overheated brakes.
Now, there are several answers to this dilemma, and being that this article is based on the aftermarket industry, there is no shortage of expensive shiny bits you can buy to battle overheated brakes. Bigger braking surfaces and high-temperature materials are one way, but that is a story I will cover in a future issue. Before spending the big bucks on filling your mags with aluminum, start with the fluid that powers the brakes. The brakes on your car are a hydraulic system, unless of course you drive a hybrid with regenerative braking, highly unlikely if you are reading this. This means that when you push the brake pedal, you are forcing fluid (an oily compound, usually DOT 3 in standard vehicles) down a line connected to a cylinder (a caliper cylinder in this case) which then squeezes increased pressure onto a spinning disc.
In normal driving circumstances, this system works just fine, but for those who like to push the limits now and then or visit the track, the standard braking system has two performance flaws. One is the rubber lines that connect from the chassis to the calipers, and the second is the fluid’s heat rating.
This first problem is mostly due to cost of manufacturing. Brake lines running from the master cylinder out to each corner are steel hard lines. However, to connect to the calipers which are suspension-mounted and constantly moving in relation to the chassis, flexible lines must be used. In everyday use, rubber lines work just fine. But when excess heat is added to the fluid, coupled with the extreme pressures of threshold braking, the rubber becomes the weak point in the system as it begins to expand, even bulging under pressure. When the rubber expands, force that is supposed to be directed to the calipers is dulled, and the sensation in the pedal mirrors this.
The answer is to replace all rubber lines with stainless steel braided lines. These are very popular modifications, so there are many different manufacturers that will make lines for just about any car. Consequently, they are also fairly cheap, ranging between $75 and $150 to do all four corners. Simply lift the car, drain the brake system, unbolt the rubber lines, and install the SS lines in their place. Refill with fluid, and bleed all calipers until no air bubbles come out, and you’re good to go. You will notice a dramatic increase in brake pedal feel and response.
As for symptom number two, you will want to refill your brake system with the proper fluid. When the brakes are used aggressively, DOT 3 brake fluid will actually come to a boil at 205 C, degrading in its ability to transfer force. Replace the fluid with a higher temperature rating such as a Ford HD DOT 3 (288 C), DOT 4 (230 C), or DOT 5.1 (270 C). DOT 5 is silicon-based fluid that requires added attention to cleaning out the system, where the Ford Heavy Duty DOT 3 drops right in and offers a better heat rating. Be sure to flush the system before replacing.
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