The SKF Dual Compound MTBDUAL-40FN seal kit represents a major evolution in the protection and performance of MTB forks. Designed specifically for Fox 40 mm forks from 2016 onwards (as well as Marzocchi Bomber 58 from 2019), this kit uses SKF's revolutionary co-molded dual-compound technology to deliver superior sealing, drastic friction reduction, and optimal contaminant exclusion. Drawing on over 10 years of SKF expertise in fork seals, this Dual Compound model pushes the boundaries with proprietary NBR compounds featuring ultra-low friction and completely redesigned lip geometries.

Dual Compound bi-material technology

The Dual Compound technology is based on the co-molding of two distinct NBR compounds with complementary properties. The green compound (wiper) offers robustness and durability while maintaining excellent grip on the stanchion, while the red compound (oil seal) is softer and more flexible, capable of adapting to micro-imperfections in the tube to maintain perfect sealing. This combination ensures ultra-smooth suspension operation while effectively blocking oil inside and contaminants outside.

Technical highlights

• Redesigned lip geometries: The sealing lip and wiper lip have been completely redesigned to improve stanchion followability, reducing friction and stick-slip in all operating conditions
• Reinforced metal insert: A new metal insert provides optimal structural support to the sealing lips, ensuring stability, longevity, and reduced fork stiction
• Self-cleaning open coil spring: Mounted on the wiper lip, this open coil spring allows mud to flow through the spiral, maintaining stable radial load and optimizing contact with the stanchion to effectively block contaminants
• NBR Super Low Friction compounds: SKF's proprietary compounds offer advanced tribological properties, minimizing resistance and maximizing suspension responsiveness
• Enhanced contaminant protection: The dual-material system combined with the self-cleaning spring provides maximum exclusion of dirt, mud, and water, protecting the fork's internal mechanisms even in the most extreme environments

Compatibility and applications

• Fox 40 Air all models: Compatible with all Fox 40 mm air forks from 2016, including DH Factory / GRIP X2 (2016-2026) and DH Performance Elite (2016-2026)
• Marzocchi Bomber 58: Compatible with Marzocchi Bomber 58 forks from 2019
• MTB enduro, DH, freeride use: Designed to withstand the extreme demands of downhill, freeride, and enduro, where performance and reliability are critical

Kit contents and installation

The MTBDUAL-40FN kit includes 2 Dual Compound oil seals, 2 foam rings, and 4 lower fork seals, everything needed to service a complete fork (two stanchions). SKF recommends thoroughly cleaning the seal housing before installation, and not lubricating the outer rubber surface of the seal (press fit) with oil, grease, or any other substance, to ensure optimal fit and sealing.

Proven performance and longevity

Thanks to its advanced compounds and sophisticated technical design, the SKF Dual Compound seal offers extended sealing capability over time, better contaminant exclusion, reliable protection of the fork's internal mechanisms, and minimal friction for optimized riding control. Field testing demonstrates superior service life and increased resistance to leaks, even under intensive use on aggressive terrain.