DIY Brake Upgrade, Part 3

This article was first published in 2004.

So far we’ve inspected the brake system for what needed to be done (DIY Brake Upgrade, Part 1), fitted new slotted discs front and back, and installed Kevlar brake pads all-round (DIY Brake Upgrade, Part 2). Now it’s time to change the fluid, bleed the brakes and then bed them in.

Changing the Fluid and Bleeding

Changing the brake fluid is a very similar process to bleeding the brakes, except you let a lot more fluid come out of the bleed nipple and you keep on filling up the master cylinder reservoir as it drops. We used Castrol Response fluid and needed two bottles – 1 litre in total.

To reduce the amount of fluid that needs to pass through the system before there’s clean fluid everywhere inside, use a turkey baster to remove fluid from the master cylinder reservoir. This one cost AUD$2.

Use the baster to drop the old fluid level and then...

...add new fluid to take it up to full again. Never let the fluid level drop below half.

Start with the brake furthest from the master cylinder. Wipe over the bleed nipple to remove any dirt and then take off the rubber protective cap.

Place a plastic hose over the bleed nipple and lead it to a clean container part-filled with brake fluid. Have someone push down on the brake pedal while you open the bleed nipple. Fluid will flow out. The old brake fluid will be a different colour – continue bleeding until fresh fluid flows out. On the first brake you may need to stop to refill the master cylinder as its level drops. Close the bleed nipple when the brake pedal is depressed. Then do the other three brakes. Once finished, the pedal should be firm, not springy.

Finally, fill the master cylinder reservoir to its full level.

Bedding-In

It’s important that new pads and discs are bedded-in before you start to work them hard.

Brake disc and caliper manufacturer Brembo makes the following suggestions:

• While the vehicle is stationary, pump brakes to ensure a firm pedal.

• Drive the vehicle cautiously to test fit and function.

• The brakes should be smooth, with no vibrations, judder, etc.

• Drive the vehicle to a remote area and perform at least 30 brake applications of 3 seconds duration. Use light/medium deceleration with varying starting speeds. Leave at least a kilometre between each brake application.

• The purpose of this procedure is to gradually increase the temperature in the components without inducing thermal shock, and to mate the brake pad and disc friction surfaces.

• After the repeated stops, drive the vehicle for several kilometres with little or no braking in order to adequately cool the components.

• After the above process is completed, the system is ready for normal use.

• When the system achieves elevated brake temperatures for the first time, a slight increase in pedal travel and pedal effort may occur. After this first "fade" and proper cooling, the system will maintain its optimum performance at all temperatures.

The Results of the Upgrade

One of the interesting things about ABS cars is that upgrading brakes is unlikely to reduce one-off emergency stopping distances. That’s because if the brakes are powerful enough to lock the wheels, the distance to a standstill depends primarily on tyres, suspension and ABS logic. And not friction at the brake discs.

However, as we found with this upgrade, nearly every other aspect of braking can be dramatically improved.

Firstly, take feel. After doing the upgrade we’ve found that the pedal is lighter for a given retardation (ie you don’t need to push as hard to brake at the same deceleration).

Secondly, progressiveness. With the new pads and discs it is much easier to brake very close to the ABS point without the ABS actually kicking in.

Thirdly, fade. The revised brakes retain their initial strong braking force even when they’re getting very hot. Put this together with the above two points and it’s easier to achieve much shorter stopping distances when the car is being driven hard.

In short, this proved to be an excellent upgrade, well worth the cost.

If your car’s brakes are getting tired, think about doing a full pad, disc and fluid upgrade, rather than just replacing the worn bits with factory parts. We highly recommend the outcome.