25mm Buggy Master Cylinder for 2 or 4 Wheel Brakes

OVERVIEW

When you are pushing your air-cooled machine to the limit, whether it is a high-speed sand rail or a street-bound performance Beetle, your braking system is the most critical safety component on the vehicle. The EMPI 25mm Buggy Master Cylinder is engineered specifically for those who have upgraded their stopping power and found their stock master cylinder lacking. Standard VW master cylinders typically feature a 17mm or 19mm bore, which often results in a "mushy" or deep pedal travel when paired with large multi-piston calipers like those from Wilwood. By stepping up to a massive 25mm bore, this unit moves a significantly higher volume of fluid with every stroke, providing the hydraulic leverage necessary to actuate 4-wheel disc brake setups with precision and authority. You will immediately notice a firmer, more responsive pedal feel that inspires confidence during aggressive driving maneuvers.

Safety is never an afterthought at Appletree Automotive, and this EMPI master cylinder delivers with a true dual-circuit design. This configuration ensures that even if a brake line is compromised or a leak occurs in one half of the system, the remaining circuit stays pressurized, allowing you to bring the vehicle to a controlled stop. Constructed from high-strength cast materials and finished to withstand the harsh environments of off-road racing and coastal environments, this master cylinder is the gold standard for custom buggy builds. It is designed to bolt directly into standard VW-style pedal clusters, making it the ultimate "big bore" solution for enthusiasts who demand the best in performance and reliability. Please note that this unit is sold individually and requires a specific reservoir, such as the EMPI 17-2878-0, to complete the installation.

FITMENT

This master cylinder is designed for universal application on vehicles utilizing Volkswagen-style pedal assemblies and is particularly suited for the following:

• VW Type 1 Bug: Custom disc brake conversions (1946-1979).
• VW Karmann Ghia: Performance builds with 4-wheel disc upgrades.
• Meyers Manx & Buggies: All years using standard VW pedal clusters.
• Sand Rails & Dune Buggies: Custom chassis with VW-style mounting.
• Baja Bugs: Ideal for heavy-duty off-road braking requirements.
• VW Type 3: Custom applications requiring increased fluid displacement.

SPECS

• Bore Size: 25mm (Large Bore for high-volume fluid displacement).
• Circuit Type: Dual Circuit (Front and Rear independent safety).
• Port Thread Size: M10 x 1.0 (Standard VW Brake Line Thread).
• Body Material: Heavy-duty cast iron for maximum durability.
• Finish: Natural / Black protective coating.
• Mounting Style: Standard 2-bolt VW pattern.
• Compatibility: Designed for use with DOT 3 or DOT 4 brake fluid.
• Total Weight: Approximately 1.89 lbs.
• Inlet Type: Designed for press-in or threaded reservoir grommets (Sold Separately).

PRO TIPS

1. The Importance of Bench Bleeding

Before you ever bolt this 25mm master cylinder to your chassis, you MUST perform a thorough bench bleed. Because of the larger bore size, air bubbles can easily become trapped in the internal piston chambers. If you attempt to bleed the system only at the wheel cylinders or calipers, you may never achieve a firm pedal. Use a bench bleeding kit to cycle fluid from the output ports back into the reservoir until every single tiny bubble is gone. This ensures that the master cylinder is 100% primed and ready to move fluid the moment it is installed on the vehicle.

2. Adjusting the Pedal Pushrod Free Play

When installing a performance master cylinder like the 98-6000-B, adjusting the pushrod that connects your brake pedal to the master cylinder is vital. You should aim for approximately 1mm of "free play" between the tip of the pushrod and the master cylinder piston. If the pushrod is too long and puts constant pressure on the piston, the compensating ports inside the master cylinder won''t open, causing your brakes to drag or even lock up as the fluid heats up and expands. Conversely, too much free play will result in "dead space" at the top of your pedal travel.

3. Pair with the Correct Fluid and Lines

Because this master cylinder is capable of generating significant hydraulic pressure, we highly recommend inspecting your entire braking system during installation. Ensure you are using high-quality stainless steel braided brake lines rather than old rubber hoses, as rubber can expand under the increased pressure of a 25mm bore, defeating the purpose of the upgrade. Additionally, always use fresh, unopened DOT 4 brake fluid to handle the higher boiling points associated with performance driving. Don''t forget to order the EMPI 17-2878-0 reservoir, as the stock VW reservoir will not fit this high-performance unit.