31/07/2003
For many car enthusiasts, there's nothing quite like spending a Sunday afternoon getting your hands dirty, delving into the intricate workings of your vehicle. While a trusty torque wrench or a comprehensive socket set are undoubtedly mainstays in any home mechanic's arsenal, there's one specialised tool that often goes overlooked until you absolutely need it: the brake rewind kit. This essential piece of kit is not just another gadget; it's a fundamental requirement for safely and effectively servicing the braking system on many modern vehicles, particularly when it comes to replacing brake pads or overhauling calipers.
Why Modern Brakes Demand a Rewind Kit
Gone are the days when most brake caliper pistons could simply be pushed back into their housing with a G-clamp or a large pair of pliers. While this method still works for some older vehicles or front calipers without integrated parking brake mechanisms, the majority of modern rear calipers, especially those equipped with an electronic parking brake (EPB) or an integrated mechanical parking brake, require a different approach. These calipers are designed so that the piston must be rotated as it is pushed back. This 'rewind' action is crucial because it aligns a screw mechanism within the caliper, allowing the piston to retract correctly and safely. Attempting to force these pistons back without rotating them can lead to significant damage to the caliper, the piston, or even the EPB motor, resulting in costly repairs that far outweigh the investment in a dedicated rewind kit.
Understanding the Caliper Piston Mechanism
To truly appreciate the necessity of a brake rewind kit, it helps to understand the internal workings of these specific calipers. Unlike simple push-back pistons, those requiring a rewind action have a threaded shaft that screws into a nut or similar mechanism inside the caliper. This threaded shaft is often connected to the parking brake lever or EPB motor. When the parking brake is engaged, this screw mechanism extends the piston to clamp the brake pads against the disc. To retract the piston for new pad installation, the screw must be unwound. This is where the rotational and pushing action of the rewind tool becomes indispensable.
What Exactly is a Brake Rewind Kit?
At its core, a brake rewind kit is a specialised set of tools designed to safely retract caliper pistons that require both rotation and compression. Typically, a comprehensive kit will include:
- Right-handed and Left-handed Threaded Rewind Tools: These are the main components, featuring a threaded rod and a handle. Some vehicles use pistons that retract with a clockwise motion, while others require an anti-clockwise motion. A good kit will provide both.
- Reaction Plate: This flat plate rests against the back of the caliper, providing a stable surface for the rewind tool to push against as it retracts the piston.
- A Variety of Adaptors: This is perhaps the most critical part of the kit. Caliper pistons come with various notch patterns or pin configurations on their face. The adaptors are designed to mate perfectly with these patterns, ensuring a secure grip and preventing damage to the piston face while it's being rotated and pushed. A versatile kit, like the Laser Brake Caliper Piston Rewind Tool, often boasts 15 or more adaptors, covering a wide range of modern European and Japanese cars.
- Storage Case: For organisation and protection of the components.
How a Brake Rewind Kit Works in Practice
The process of using a brake rewind kit is relatively straightforward once you understand the principle. After safely lifting your vehicle and removing the wheel, you'll typically remove the brake caliper from its mounting bracket. With the old brake pads removed, you select the appropriate adaptor from your kit that matches the pattern on your caliper piston. This adaptor is then attached to the end of the threaded rewind tool. The reaction plate is positioned against the opposite side of the caliper body. By turning the handle of the rewind tool, the threaded rod extends, pushing the adaptor against the piston. Simultaneously, the adaptor's pins engage with the piston's notches, causing it to rotate as it retracts into the caliper housing. This dual action ensures the internal screw mechanism is correctly unwound, allowing the piston to fully retract and make space for the new, thicker brake pads.
Step-by-Step Guide: Using Your Brake Rewind Kit
Performing a brake pad replacement with a rewind kit requires patience and attention to detail. Always prioritise safety first.
- Preparation and Safety First: Park your car on a level surface, engage the handbrake, and loosen the wheel nuts on the wheel you'll be working on. Safely lift the vehicle using a reliable jack, like the Halfords Advanced 3 Tonne Low Profile Trolley Jack, and secure it with sturdy axle stands, such as the Halfords Advanced 3 Tonne Ratchet Axle Stands. Remove the wheel completely.
- Access the Caliper: Depending on your vehicle, you may need to turn the steering wheel to gain better access to the caliper. Carefully remove the two bolts that hold the caliper to its mounting bracket. Ensure you don't damage the brake hose; never let the caliper hang by the hose. Use a bungee cord or wire to suspend it from the suspension strut.
- Remove Old Pads: Slide out the old brake pads. Note how they sit in the caliper for correct re-installation of the new ones.
- Prepare for Rewind: Before retracting the piston, check the brake fluid reservoir under the bonnet. If it's full, you may need to remove a small amount of fluid using a syringe to prevent overflow when the piston is pushed back. Place a rag around the reservoir to catch any spills, as brake fluid can damage paintwork.
- Select and Attach Adaptor: Identify the correct adaptor from your rewind kit that matches the face of your caliper piston. Attach it firmly to the rewind tool.
- Position the Tool: Place the reaction plate against the back of the caliper body. Insert the adaptor end of the rewind tool into the caliper opening, ensuring the adaptor pins engage correctly with the piston's notches.
- Rewind the Piston: Begin turning the handle of the rewind tool. You should feel the piston slowly retracting while simultaneously rotating. Keep turning until the piston is fully seated back into the caliper housing, flush with the caliper body.
- Install New Pads: Once the piston is fully retracted, install your new brake pads, ensuring they are seated correctly within the caliper bracket.
- Reassemble Caliper: Carefully position the caliper back over the new pads and brake disc. Re-insert and tighten the caliper mounting bolts to the manufacturer's specified torque using your torque wrench.
- Final Steps: Re-mount the wheel, lower the vehicle safely, and tighten the wheel nuts to specification. Crucially, before driving, pump the brake pedal several times until it feels firm. This re-seats the pistons against the new pads. Check the brake fluid level again and top up if necessary.
Common Issues and Troubleshooting
While using a brake rewind kit is generally straightforward, you might encounter a few hiccups:
- Piston Not Retracting: Ensure you're using the correct adaptor and that its pins are fully engaged with the piston. Check if you're turning it in the correct direction (clockwise or anti-clockwise). Some pistons can be stubborn due to corrosion; a little penetrating fluid around the piston boot might help, but avoid getting it on the piston face or rubber seals.
- Brake Fluid Overflow: If you didn't remove enough fluid from the reservoir before starting, it might overflow as the piston retracts. Wipe up spills immediately and top up if needed after the job is done.
- Damaged Piston Boot: Be careful not to tear the rubber piston boot while working. If it's damaged, it must be replaced to prevent moisture and dirt from entering the caliper, which can lead to seizing.
- Electronic Parking Brake (EPB) Issues: For vehicles with EPB, simply retracting the piston with a rewind tool might not be enough. Many EPB systems require being put into 'service mode' via a diagnostic tool before the pistons can be retracted. Failure to do so can damage the EPB motor or trigger fault codes. Always consult your vehicle's service manual.
Comparison of Caliper Piston Types
Understanding the difference between piston types is key to successful brake maintenance:
| Piston Type | Common Location | Retraction Method | Tools Required |
|---|---|---|---|
| Push-Back Piston | Front calipers, older rear calipers | Direct compression | G-clamp, large pliers, or dedicated push-back tool |
| Rewind Piston | Rear calipers (with integrated parking brake or EPB) | Rotation and compression simultaneously | Brake rewind kit (with appropriate adaptors) |
Frequently Asked Questions (FAQs) About Brake Rewind Kits
- Can I replace my brake pads without a brake rewind kit?
- For vehicles with 'rewind' type rear calipers, absolutely not. Attempting to force these pistons back without rotating them will cause internal damage to the caliper and could lead to brake failure or expensive repairs. It's an indispensable tool for these specific applications.
- How do I know if my car needs a brake rewind kit?
- The easiest way to tell is if your car has an integrated mechanical parking brake on the rear calipers, or an electronic parking brake (EPB). If the face of the rear caliper piston has notches or cut-outs (rather than being smooth), it almost certainly requires a rewind tool. Always check your vehicle's service manual or a reliable online resource for your specific model.
- Are all brake rewind kits universal?
- While many kits are sold as 'universal' due to their wide range of adaptors (like the 18-piece Laser kit), the term refers to the variety of vehicles they can service, not that one tool fits all. You'll still need to select the correct adaptor for your specific piston pattern. Some very specific vehicle models might require a dedicated, brand-specific tool.
- What's the difference between a right-handed and left-handed rewind tool?
- This refers to the direction the piston needs to be rotated to retract. Some manufacturers design their calipers to unwind clockwise, others anti-clockwise. A comprehensive kit provides both, ensuring compatibility with a broader range of vehicles.
- Do I need to bleed my brakes after replacing pads with a rewind kit?
- Typically, a simple pad replacement where the hydraulic lines are not disconnected does not require a full brake bleed. However, it's always good practice to pump the brake pedal several times to re-seat the pistons against the new pads before driving. If the pedal feels spongy, or if you had to open the bleed nipple for any reason, then a full bleed using a tool like the Europat Vizibleed Brake and Clutch Bleeding Kit would be necessary.
Conclusion
For the dedicated home mechanic, the brake rewind kit isn't just a convenience; it's a necessity for safe and proper brake maintenance on many modern vehicles. Investing in a quality kit, understanding its function, and following correct procedures will not only save you money on garage labour but also give you the satisfaction of knowing your vehicle's most critical safety system is in top condition, thanks to your own efforts. So, next time you're planning a brake job, ensure this indispensable tool is part of your arsenal. With the right kit and a bit of know-how, you'll be able to tackle brake pad replacements with confidence, keeping your car running smoothly and, most importantly, safely.
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