Combating Brake Fade’s Hidden Culprit: Caliper Piston Pucks
When discussing brake fade on a Porsche GT3, GT3 RS, Turbo, or GT4, most of the attention goes to brake pads, rotors, fluid, and cooling. One component that receives far less attention is located directly between the brake pad and the caliper piston: the caliper piston puck.
Porsche uses these insulating pucks for an important reason. They create a thermal barrier between the extremely hot brake pad and the aluminum caliper piston, helping reduce the amount of heat transferred into the piston, caliper, and ultimately the brake fluid.
For cars that see significant track use, their condition can have a meaningful effect on brake-system performance.
Why Porsche Uses Piston Pucks
During hard braking, a tremendous amount of kinetic energy is converted into heat at the brake rotor and pad.
Brake-pad temperatures can become extremely high during sustained track use. Without some form of thermal isolation, that heat has a relatively direct path from the brake pad into the piston and then into the brake fluid.
Porsche’s solution on these calipers is a coated aluminum piston combined with a separate insulating puck at the pad interface.
Aluminum makes sense for the piston itself. It is lightweight and its thermal expansion characteristics are well suited to an aluminum brake caliper. Its disadvantage is that aluminum is also an excellent conductor of heat.
The puck provides the thermal break.
Rather than allowing the brake pad to bear directly against the aluminum piston, the insulating puck reduces the rate at which heat can travel from the pad into the piston.
The Problem With the Factory Ceramic Pucks
The original Porsche ceramic pucks provide excellent thermal insulation, but ceramic has an inherent disadvantage in a racing environment: it is brittle.
Repeated heat cycles, vibration, pad changes, track debris, handling during brake service, and the mechanical loads generated during braking can eventually cause the ceramic material to crack, chip, or break.
A damaged puck may no longer properly support the brake pad or provide the thermal protection intended by the original design.
This is why Demon Speed recommends inspecting the piston pucks whenever the brake pads are removed.
A puck with visible cracking, chipping, or other damage should be replaced.
Why Not Simply Use a Solid Metal Puck?
Replacing a broken ceramic component with metal sounds simple, but the material selected for the replacement matters.
The puck is not merely a spacer. It is part of the brake system’s thermal-management strategy.
A highly conductive replacement material can create a more effective heat path from the brake pad into the aluminum piston. That heat can then travel into the brake fluid.
As brake-fluid temperature increases, the margin between normal operation and fluid boiling decreases. Once brake fluid begins producing vapor, the result can be the long or soft pedal commonly associated with brake fade.
For that reason, Demon Speed approached the replacement puck as a thermal-management component, not simply as a piece of hardware that needed to be strong enough to replace the ceramic part.
Demon Speed’s Replacement Puck Development
Demon Speed developed a replacement piston puck specifically for Porsche track and race applications.
Our objective was to address the primary weakness of the original ceramic component—its brittleness—while retaining strong thermal-isolation characteristics.
We evaluated replacement materials through real-world track use, not simply by comparing published material specifications.
The result is the material used in our Demon Speed pucks today.
We intentionally do not publish the exact alloy specification, but based on our testing and experience, it is the material we prefer for this application.
It provides the durability we wanted while maintaining excellent resistance to heat transfer into the aluminum caliper piston.
Demon Speed Material vs. Titanium
Titanium has become a popular material for brake thermal barriers and piston components, and for good reason. Compared with materials such as steel and aluminum, titanium has relatively low thermal conductivity while offering excellent strength and temperature resistance.
Demon Speed offers Grade 5 titanium pucks for customers who prefer titanium.
However, based on our own real-world testing, we prefer the Demon Speed proprietary-material puck for this application.
Both are significant upgrades when replacing damaged factory ceramic pucks, but our testing has led us to favor the thermal characteristics of the Demon Speed material.
That is why we continue to offer both choices while using the Demon Speed material as our preferred solution.
The Retaining Screw Is Also a Heat Path
There is another component in this system that is easy to overlook: the screw that attaches the puck to the piston.
The pucks are retained with an M5 x 0.8 flat-head screw threaded into the coated aluminum caliper piston.
The puck itself may provide excellent thermal isolation, but the retaining screw still creates a small conductive path between the hot puck assembly and the aluminum piston.
Demon Speed therefore offers two retaining-screw options.
Carbon Steel is the standard replacement option.
Titanium is available for customers looking to further reduce conductive heat transfer through the retaining hardware.
Titanium’s lower thermal conductivity makes it particularly attractive here because reducing heat transfer is the entire purpose of the puck assembly.
Suggested Retaining Screw Installation
The M5 retaining screw is only securing the puck to the piston. It is not a structural brake-caliper fastener and should not be aggressively tightened.
Demon Speed recommends a suggested tightening torque of approximately 3 N·m (27 in-lb).
In practice, access and tool geometry can make using a torque wrench difficult. The important point is to install the screw snugly and evenly without excessive force.
The screw threads into an aluminum piston. Over-tightening can damage the piston threads.
The 3 N·m figure should therefore be considered a conservative installation guideline rather than a Porsche factory torque specification.
Different Porsche Applications Use Different Puck Sizes
Porsche has used more than one piston-puck configuration, so replacement pucks should not be selected based solely on appearance.
Earlier applications use:
| Position | Puck Diameter |
|---|---|
| Front | 30 mm |
| Rear | 34 mm |
These earlier-style pucks are found across applicable Porsche 981/718 GT4 and GT4 RS, 991 GT3/GT3 RS, 991 Turbo/Turbo S and related applications.
Exact fitment should always be confirmed before ordering.
2023+ 992 Revised Piston Pucks
Beginning with later 992 applications, Porsche revised the piston and puck geometry.
Applicable 2023+ 992 GT3, GT3 RS, and Turbo S cars use:
| Position | Puck Diameter | Design |
|---|---|---|
| Front | 32 mm | Revised geometry |
| Rear | 34 mm | Revised geometry |
The later pucks use a curved/sloped outer profile with a reduced contact area against the brake pad.
Importantly, this change applies to both the front and rear pucks.
That means there are now two different 34 mm rear puck designs.
An earlier 34 mm rear puck and a later 2023+ 992 34 mm rear puck may share the same nominal diameter, but they do not have the same geometry.
For that reason, diameter alone should not be used to select the correct replacement.
Why Porsche Changed the Geometry
The revised geometry reduces the area of direct contact between the puck and brake pad.
While Porsche does not necessarily publish the engineering reasoning behind every detail of the design, reducing the contact area is consistent with the overall objective of limiting conductive heat transfer from the brake pad into the piston.
Demon Speed’s later 992 replacement pucks retain this revised sloped geometry rather than simply substituting a flat puck of the correct diameter.
That allows the replacement to preserve the important physical characteristics of the later factory design.
Inspect the Pucks During Every Pad Change
For cars that see regular track use, we recommend making puck inspection part of normal brake service.
When the pads are removed, inspect each puck for:
- Cracks
- Chips
- Missing material
- Abnormal wear
- Damage around the retaining screw
- Loose retaining screws
- Uneven seating against the piston
This inspection takes very little additional time when the pads are already out of the caliper.
Finding a damaged puck in the shop is considerably preferable to discovering a brake problem during a track session.
Don’t Forget the Brake Fluid
Piston pucks are only one component of the brake system’s overall thermal-management strategy.
Proper track preparation should also include high-quality brake fluid, appropriate fluid-change intervals, adequate brake cooling, proper pad selection, and inspection of the calipers, seals, pistons, rotors, and brake lines.
The objective is not simply to keep the brake pads working. It is to control how much heat reaches the hydraulic side of the braking system.
The piston puck is the last significant thermal barrier between the brake pad and the caliper piston, making this small component more important than its size suggests.
Demon Speed Replacement Caliper Piston Pucks
Demon Speed offers replacement caliper piston pucks for applicable Porsche GT3, GT3 RS, Turbo, Turbo S, GT4, GT4 RS and related applications.
Depending on application, options include:
- Demon Speed proprietary-material pucks
- Grade 5 titanium pucks
- Carbon-steel retaining screws
- Titanium retaining screws
- Earlier 30 mm front / 34 mm rear configurations
- Later 32 mm front / 34 mm rear revised-geometry configurations
Always select replacement pucks based on the vehicle application, axle position, puck diameter, and puck geometry.
For cars near a model-year or design transition, inspect and measure the existing components before ordering.