GXC,RD2 and MTC Hub End Caps

Switching the modular designed press-in end caps on the compatible Halo front hubs will enable the hub to be fitted into different forks. For example: changing a 12mm Thru axle GXC hub to work with a 15mm Thru axle fork, or, enabling a Boost 15mm Thru axle MTC hub to fit with a ‘Boost QR’ fork.

Important: These end caps are only designed to fit the noted Halo front hub models: RD2, GXC and MTC – no other hubs are compatible.

Note:

These hub caps do not affect the effective width of the hub/fork standard being used.

For Disc brake forks, width fitting (hub spacing) compatibility is primarily dictated by the disc mount spacing location standard of the fork.  (This is the width between the 2 inner faces of the fork dropouts that locate the hub)

There are typically 2 common front hub/fork spacing options in use for modern Road and MTB bikes:  100mm and Boost 110mm

100mm: is the Road bike standard and also the classic MTB spacing.

Boost* 110mm: is the later MTB standard.

(*Note: Boost 110m is not to be confused with classic Downhill MTB 110mm – which uses the classic Disc mount spacing location, and is not cross compatible) 

Halo RD2 and GXC front hubs use the spacing standard of 100mm.

Halo MTC front hubs use the Boost 110mm spacing standard.

Also please note there are 2 different 15mm Thru-axle type end cones: 15/19mm and 15/21mm.

The key difference relates to the out diameter of the end cap, which can be important depending on the location recess size of the fork dropout.  Typically, the location recess in an MTB fork dropout accepts an end cap of up to 21mm external diameter.  Several Road and Cross/Gravel forks now use a smaller dropout recess allowing a maximum outer diameter cap of 19mm.  This smaller recess size derives primarily from the use of increasingly popular use of the smaller/lighter 12mm Thru axle diameter instead of the MTB based 15mm Thru axle size for road bikes.  Bear in mind that a 19mm cap can usually be used in a 21mm recess, but, a 21mm cap cannot be fitted into a 19mm recess.

End Cap selection options:

12mm Thru-axle ‘road’ type forks:

Closed hole dropouts with a 12mm Thru axle and 19mm hub recess

select: Item#:  HUHAZGXFA2 – 12/19mm

15mm Thru-axle ‘road’ type forks: 

Closed hole dropouts with a 15mm Thru axle and 19mm hub recess

select: Item#:  HUHAZGXFA5 – 15/19mm

15mm Thru-axle ‘MTB’ type forks: 

Closed hole dropouts with a 15mm Thru axle and 21mm hub recess

select: Item#:  HUHAZGXFAM – 15/21mm

QR type forks:

9mm open slot dropouts that use a 5mm diameter ‘skewer’ rod (QR).

select: Item#:  HUHAZGXFAQ – QR5/9