HKS 12999-AK001 GT Supercharger Pulley 8-Rib 80mm for HKS GTS4025 GTS7040

Vehicle Fitment

• Universal - compatible with HKS GT Supercharger Universal Type units: GTS4025, GTS7040, GTS8550, and GTS8555
• No vehicle-specific fitment - this pulley is selected based on the GT Supercharger unit installed and the desired boost level, not the vehicle make/model directly
• Confirm compatibility with your specific HKS GT Supercharger unit and kit configuration before ordering

Fitment Notes

• Pulley diameter directly determines supercharger speed relative to engine RPM - an 80mm pulley produces a specific boost output level; selecting a smaller diameter pulley will increase supercharger speed and boost output, while a larger diameter pulley will decrease it
• Designed for use with 8-rib serpentine belt systems - verify your GT Supercharger kit uses an 8-rib belt configuration before ordering
• Supercharger unit not included - this is a replacement or upgrade pulley only
• For a larger pulley option, see HKS part number 12999-AK005 (8Rib-100mm)
• Intended for competition and racing use - not legal for use on pollution-controlled street vehicles in all jurisdictions; verify local emissions regulations before purchasing

Features

• 80mm diameter, 8-rib design - provides the belt contact area and grip needed to transfer drive force from the engine to the GT Supercharger unit without belt slip under high load
• Allows tuners to adjust the supercharger's drive ratio - changing from the stock pulley to an 80mm unit alters the supercharger's rotational speed relative to engine RPM, enabling boost level tuning without changing the supercharger unit itself
• Compatible with HKS GT Supercharger Universal Type units GTS4025, GTS7040, GTS8550, and GTS8555 - covers the full range of HKS centrifugal GT Supercharger platforms
• Black finish for a clean underhood appearance
• Genuine HKS GT Supercharger accessory part - manufactured to the same standards as components supplied with the original GT Supercharger kit
• The HKS GT Supercharger's centrifugal design delivers lag-free, linear power delivery - boost builds smoothly with RPM, producing stable torque across the full RPM range from low to high

Specifications

• Part Number: 12999-AK001
• Type: GT Supercharger Drive Pulley
• Rib Count: 8-rib
• Diameter: 80mm
• Finish: Black
• Compatible Supercharger Units: HKS GTS4025, GTS7040, GTS8550, GTS8555
• Fitment: Universal (GT Supercharger system-specific, not vehicle-specific)
• Quantity: 1 pulley

Included Components

• 1x HKS GT Supercharger Pulley (8-Rib, 80mm, Black)

Product Description

The HKS 12999-AK001 is an 8-rib, 80mm diameter drive pulley for HKS GT Supercharger Universal Type units - compatible with the GTS4025, GTS7040, GTS8550, and GTS8555 platforms. The pulley is a key tuning component in any GT Supercharger installation: by changing pulley diameter, tuners can adjust the supercharger's rotational speed relative to engine RPM, directly controlling boost output without modifying the supercharger unit itself. A smaller diameter pulley spins the supercharger faster and produces more boost; a larger diameter pulley reduces supercharger speed and boost output.

The 8-rib design provides the belt contact area needed for reliable power transfer under sustained high-load operation, minimizing the risk of belt slip that can occur with narrower rib configurations at high boost levels. The HKS GT Supercharger's centrifugal design delivers lag-free, linear power delivery - boost builds proportionally with RPM for smooth, predictable torque output across the entire rev range. Intended for competition and racing use. Genuine HKS part, manufactured in Japan.