Brake Caliper Piston, Rear. Porsche 911 Carrera 3.2L 1984-89, 42mm diameter x 30mm height › 91135242X00

Brake Caliper Replacement Pistons for Brembo Calipers 
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Restore the performance and reliability of your Porsche Brembo braking system with these OE Match Brake Caliper Replacement Pistons. Manufactured to original equipment specifications, these precision-engineered pistons are designed for rebuilding Brembo brake calipers fitted to a wide range of Porsche models.

Available in 28mm, 30mm, 32mm, 34mm, 36mm, 38mm, 40mm and 44mm outer diameters, every piston has an overall height of 32mm and is manufactured to deliver the correct fit, smooth operation and dependable sealing performance when used with new piston seals and dust boots.

Important: Please check the piston diameter required for your specific caliper before ordering. Many Brembo calipers use two different piston diameters within the same caliper to optimise braking performance. The sizes listed refer to the outer diameter (OD) of the piston.

What Does a Brake Caliper Piston Do?

The brake caliper piston is one of the most important components inside the braking system. Hydraulic brake fluid pressure pushes the piston forward, forcing the brake pad firmly against the brake disc to generate the friction required to slow or stop the vehicle.

Its primary functions include:

• Converting hydraulic pressure into braking force.
• Applying even pressure across the brake pads.
• Ensuring smooth and consistent piston movement.
• Maintaining balanced braking performance.
• Supporting Porsche ABS and stability control systems.
• Delivering precise pedal feel and braking response.

Correctly functioning pistons are essential for maintaining the powerful, progressive braking performance expected from Porsche Brembo calipers.

Why Do Brake Caliper Pistons Fail?

Brake caliper pistons operate in harsh conditions and are continually exposed to heat, moisture and brake dust. Over time they can become damaged or worn.

Common causes include:

• Corrosion caused by moisture ingress.
• Torn or damaged dust boots.
• Contaminated brake fluid.
• Surface pitting.
• Heat generated during heavy braking.
• Seized pistons caused by corrosion.
• Damage during previous repairs.
• High mileage and normal wear.

A damaged piston can prevent the caliper from operating correctly, leading to reduced braking performance and uneven brake pad wear.

Symptoms of a Worn or Damaged Caliper Piston

Common symptoms include:

• Sticking or seized brake calipers.
• Uneven brake pad wear.
• Vehicle pulling during braking.
• Reduced braking performance.
• Overheating brakes. Brake drag.
• Fluid leaks around the piston seal.
• Difficulty retracting the piston during servicing.

Replacing damaged pistons during a caliper overhaul restores smooth operation and reliable braking performance.

When Should Brake Caliper Pistons Be Replaced?

Replacement is recommended whenever:

• Corrosion or pitting is visible.
• Pistons become seized or difficult to move.
• The caliper is being rebuilt.
• Dust boots have failed allowing contamination.
• Brake fluid leaks occur around the piston.
• Uneven pad wear is caused by sticking pistons.
• Restoring older Brembo brake calipers.
• During preventative maintenance on ageing braking systems.

For the best results, new pistons should always be installed with new piston seals and dust protection boots.

OE Match Quality You Can Trust

These OE Match Brake Caliper Replacement Pistons offer:

• Manufactured to original equipment specifications.
• Precision-machined finish.
• Excellent corrosion resistance.
• Smooth piston movement.
• Direct replacement fitment.
• Suitable for Brembo brake calipers.
• Available in 28mm, 30mm, 32mm, 34mm, 36mm, 38mm, 40mm and 44mm diameters.
• Uniform piston height of 32mm.
• Ideal for professional caliper rebuilding.