Sanding Discs for GPFAX Pads: A Crucial Step

Do I Need to Sand My Discs Before Installing GPFAX Pads?

When upgrading your motorcycle's braking system, especially with high-performance components like EBC's GPFAX race pads, understanding the installation process is paramount. One common question that arises, particularly when switching from carbon-based pads to a sintered compound like the GPFAX, is whether the brake discs need to be prepared. The short answer, as highlighted in the technical notes for EBC GPFAX pads, is often yes. This article delves into why this preparation is necessary, the benefits it offers, and what can happen if this crucial step is overlooked.

Understanding Brake Pad Materials: Sintered vs. Carbon

EBC's GPFAX pads are renowned for their world-class performance, offering instant stopping power, extreme high-temperature fade resistance, and superb feel. They are a sintered compound, meaning the friction material is fused together using heat and pressure. This process creates a durable, high-friction material that performs exceptionally well under demanding conditions, such as track racing.

Historically, some high-performance applications have also utilised carbon-based brake pads. While carbon pads can offer excellent initial bite and light weight, they have their own set of characteristics and maintenance requirements. One of the key differences lies in how they interact with the brake disc surface.

The Glaze Phenomenon: Why Sanding is Necessary

When carbon-based brake pads are used, they can leave behind a thin, hard layer on the surface of the brake disc. This layer is often referred to as a 'glaze'. While this glaze might not immediately present a problem with the carbon pads themselves, it can significantly hinder the performance of a new, sintered compound like the GPFAX pads. The sintered material relies on direct, aggressive contact with the disc surface to achieve its optimal friction coefficient.

The technical note from EBC explicitly states: "If Carbon based pads were in use before GPFAX pads are installed, to gain the full braking effect and to prevent and judder, the disc must be fine sanded with abrasive paper or wire wool to remove the grey glaze that carbon pads lay down (this is a normal when changing to any sintered pad from carbon)."

This means that the glaze left by carbon pads acts as a barrier. It reduces the surface area of contact between the new GPFAX pads and the disc, leading to:

• Reduced Braking Power: The pads cannot grip the disc effectively, resulting in less stopping power than expected.
• Judder and Vibration: The uneven contact caused by the glaze can lead to vibrations felt through the handlebars and brake lever, commonly known as judder.
• Inconsistent Feel: The feedback from the brake lever will be less predictable, compromising rider confidence.
• Premature Wear: The pads may wear unevenly as they struggle to overcome the glazed surface.

The Benefits of Pre-Installation Disc Preparation

Sanding your discs before fitting GPFAX pads offers several significant advantages:

How to Prepare Your Discs

The process is relatively straightforward:

1. Remove the Old Pads: Carefully unbolt and remove the old brake pads from the calipers.
2. Clean the Caliper Area: While the pads are out, it's a good opportunity to clean any debris from around the caliper mounting points and pistons.
3. Sand the Disc Surface: Use fine-grit abrasive paper (e.g., 240-400 grit) or a good quality wire wool. Gently but firmly rub the surface of the brake disc in a circular or cross-hatch pattern. Ensure you cover the entire braking surface evenly. The goal is to remove the shiny, glazed layer and expose fresh metal.
4. Clean Thoroughly: After sanding, use a dedicated brake cleaner to thoroughly clean the discs, removing all dust and residue from the sanding process. Ensure the discs are completely dry before proceeding.
5. Install New Pads: Fit the new EBC GPFAX pads according to the manufacturer's instructions.

What if I Don't Sand the Discs?

Ignoring the recommendation to sand the discs can lead to a suboptimal braking experience. You might notice:

• The brakes don't feel as sharp or powerful as they should.
• A gritty or juddering sensation when braking.
• The new pads may not bed in correctly.
• Potentially, premature wear on the new pads and discs due to inconsistent contact.

While the GPFAX pads are designed to be quickly usable with a minimal bedding-in process, this efficiency is best achieved on a properly prepared surface. The performance testimonials for GPFAX pads, from multiple championship wins to personal best lap times, are a testament to their capabilities when installed correctly.

Bedding-In GPFAX Pads

Even with properly prepared discs, the bedding-in process is important for any new brake pads. EBC states that GPFAX pads require a minimal bedding-in process. Typically, this involves:

• Applying the brakes moderately several times while riding at a low speed.
• Gradually increasing the braking intensity over a few miles.
• Allowing the brakes to cool down completely without holding the lever down.

The GPFAX pads are designed to offer high friction from cold, but this initial performance is enhanced and made more consistent through proper bedding.

Important Considerations for GPFAX Pads

It's crucial to remember the specific application for GPFAX pads:

• Track Use Only: These pads are designated as "NOT FOR ROAD USE." Their high friction levels are intended for use with race tyres and on surfaces with high adhesion. Using them on the road could be dangerous and may invalidate your insurance as they are not ECE R 90 approved.
• Compatibility: While compatible with original or aftermarket steel discs, always ensure your discs are in good condition and within manufacturer tolerances for thickness and run-out.
• Money Back Guarantee: EBC and its distributors often offer guarantees on their products. If you follow their advice and are not satisfied, it's worth enquiring about these options.

Frequently Asked Questions

Q1: My current pads are not carbon, can I skip sanding?

A1: If you are switching from another type of sintered or organic pad, and your discs appear to be in excellent condition with no glazing or damage, sanding might not be strictly necessary. However, a light scuffing with fine sandpaper or brake cleaner is always recommended to ensure the best possible surface for the new pads.

Q2: What grit sandpaper should I use?

A2: A fine grit sandpaper, typically between 240 and 400 grit, is recommended. You want to remove the glaze without aggressively removing disc material.

Q3: Can I use a wire brush instead of sandpaper?

A3: A good quality wire wool or a brass wire brush can be effective. Avoid using a steel wire brush, as it can embed harder particles into the disc surface. The goal is to abrade the glazed layer, not to aggressively machine the disc.

Q4: How much pressure should I apply when sanding?

A4: Apply firm, even pressure. You should be able to see the shiny glaze disappear and a duller, more uniform metal surface emerge.

Q5: Do I need to sand new discs if I'm fitting GPFAX pads for the first time?

A5: New discs usually come with a protective coating or a slight manufacturing glaze. It's good practice to clean them thoroughly with brake cleaner. Some manufacturers recommend a light scuffing of new discs to ensure optimal pad material transfer from the very first application.

Conclusion

When upgrading to high-performance EBC GPFAX brake pads, taking the small but significant step of preparing your brake discs is crucial, especially if you're moving from carbon pads. Sanding the discs removes the glaze that can impede performance, ensuring you can fully benefit from the exceptional stopping power, feel, and consistency that these race-proven pads offer. Properly installed and bedded-in, GPFAX pads provide a competitive edge and enhanced rider confidence on the track. Always adhere to the manufacturer's technical guidelines for the best results.

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