The Shimano Deore FH-M595 left-side locknut unit (reference Y3SW98030) is an essential original spare part for the maintenance and repair of Shimano rear hubs. Designed for demanding enthusiasts and professional workshops, this complete unit includes the bearing cone, the spacer and the locknut, ensuring optimal reliability and perfect compatibility with several generations of Deore hubs and related systems.

Technical Summary

This left-side locknut unit is part number 6 in the official Shimano exploded diagrams for the FH-M595 hub. It is an integral part of the angular contact bearing adjustment system that ensures smooth rotation of the rear wheel. Classified as category A compatibility by Shimano, this part is strictly identical in materials, finish and dimensions for all referenced compatible hubs, which eliminates any risk of approximation during replacement.

Technical Highlights

• Extended official compatibility: beyond the FH-M595, this unit fits perfectly on Deore FH-M6000, FH-M615 hubs and complete WH-MT35 wheels (all variants 27.5", 29" and standard), ensuring maximum versatility for your workshop
• Reinforced construction: manufactured from high-strength steel with anti-corrosion finish, it withstands daily stress, shocks and extreme weather conditions
• Optimized bearing system: the cone and locknut allow micrometric adjustment of bearing play, essential for smooth operation and increased hub longevity
• Labyrinth seal sealing: integrates with the FH-M595 labyrinth seal system, effectively protecting bearings against mud, water and contaminants

FH-M595 Hub Features

The Deore FH-M595 hub is a disc rear hub developed in 2009, belonging to the Shimano Deore M590 group. It is distinguished by its lightweight freehub body, its Center Lock mounting for brake disc, and its compatibility with 8, 9 or 10-speed cassettes. The standard 135 mm spacing (OLD) and quick release system make it a versatile reference for cross-country and all-mountain MTB.

Geometry and Standards

• Spacing (Over Locknut Dimension): 135 mm (5-5/16")
• Complete axle length: 146 mm (5-3/4")
• Mounting system: Quick Release
• Brake mounting: Center Lock (6-bolt rotor not compatible)
• Bearings: 1/4" (6.35 mm) ball bearings, adjustable by angular contact

Installation and Maintenance

Replacing the left-side locknut unit requires thin hub cone wrenches (typically 13, 15 or 17 mm depending on model). The operation consists of unscrewing the old locknut, removing the worn cone, thoroughly cleaning the axle, then installing the new cone while ensuring the assembly order is respected: cone → spacer → locknut. Final adjustment of bearing play must be carried out with precision: the hub must rotate freely without perceptible axial play. Application of teflon bearing grease is recommended to ensure durability.

Advantages for Workshop and Cyclist

• Economical repair: replacing this unit significantly extends the hub's service life without investing in a complete wheel
• Certified original part: guaranteed Shimano quality, without approximation or compromise on performance
• Accessible installation: with minimal tools and know-how, this repair is within reach of experienced cyclists
• Safety stock: ideal part to keep in the workshop for quick interventions on 2009-2017 Deore hubs