We get questions on a regular basis about the nomenclature used in specifying Onyx Racing Products hub models. To clear – and hopefully prevent – confusion, the most used terms and abbreviations are listed below. Some of them are self-explanatory, while some are quite specific and might warrant further explanation.
Boost spacing – Quite self-explanatory: 15x110mm spacing in the front, and 12x142mm spacing in the rear.
CL – Centerlock disc mount standard, introduced by Shimano in the early 2000s.
FAT – The abbreviation used in conjunction with hubs manufactured in fat bike-specific axle spacing, e.g. 15x150mm front hub, and 12x197mm rear hub.
HG – Hyperglide, the oldest cassette and freehub driver/body interface that’s still in use.
HGSS – Single-speed specific Hyperglide driver. The interface is identical to the standard Hyperglide version, but the driver body itself is shorter, thus allowing (nearly) symmetrical flange spacing, and thus a stronger wheel.
HK – Hook Flange, the hub flange structure designed specifically for Berd Spokes.
ISO – ISO 6-bolt. The most common disc rotor mounting standard.
MS – Shimano Micro Spline cassette-driver interface, the newest standard in this domain.
MTB spacing – The “old-style” spacing used in mountain bike hubs: 100x15mm in the front, and 142x12mm in the rear. It’s worth noting that the MTB spacing covers the standard 100x12mm front hub spacing used in road and gravel bikes.
SSD – The disc-specific version of the Ultra SS BMX rear hub, the pinnacle of BMX racing hubs.
RS-1 – A front hub specifically designed to be used with the RS-1 fork by Rock Shox, the cross-country model with USD design.
TC – Torque cap. A standard used in axle-dropout interface is used in nearly all Rock Shox forks. It’s also found on some models by other manufacturers, e.g., EXT.
XDR – A wider version of the XD driver standard. All Onyx hubs that employ the MFU axle design are supplied with an XDR driver (if chosen), which can be converted to XD using the 1.85mm spacer provided with the hub.