SR Suntour fork top cap socket (FAA122/FAA086 replacement)

I recently attended bike tech workshops through the Professional Bike Mechanics Association (PBMA) where I received training in a whole bunch of different things from many different brands. I was constantly thinking "I bet I can 3D print that" and this is the first of several things I'll be posting which were inspired by these seminars.

SR Suntour makes a wide range of forks, but most folks have seen their forks in the form of the heavy steel forks like the XCT which are found on many entry-level bikes, mountain bikes, hybrids, etc. I previously thought of these forks as pretty low quality, but that's not fair, or accurate. Turns out that they are inexpensive, but they also have some brilliant features that make them completely serviceable. In particular, the design of the bushings is brilliant, they can be removed with a screwdriver and quickly replaced. To do this maintenance, you need the FAA122 tool, which you can see in the photos. Considering the FAA122 is plastic, I immediately saw the possibility of printing one, and at that point, turning it into a socket seemed like the obvious way to go.

The torque spec on the socket is only 10 Nm, and with so many points of engagement on the splines, this tool can handle that easily. I could probably even print it with a 3/8" socket drive and not have issues, but the 1/2" is stronger as it spreads the drive forces over a larger radius, thus reducing the stress on the socket.

Thanks to Jon Wells of Envelo for his help in this project!

Thanks also to jaybeckr for modifying this to work as an FAA086 replacement as well - I've included his STL.

Fusion 360 F3D file included if you want to change anything.

Print instructions

Category: Hand Tools Summary

I recently attended bike tech workshops through the Professional Bike Mechanics Association (PBMA) where I received training in a whole bunch of different things from many different brands. I was constantly thinking "I bet I can 3D print that" and this is the first of several things I'll be posting which were inspired by these seminars.

SR Suntour makes a wide range of forks, but most folks have seen their forks in the form of the heavy steel forks like the XCT which are found on many entry-level bikes, mountain bikes, hybrids, etc. I previously thought of these forks as pretty low quality, but that's not fair, or accurate. Turns out that they are inexpensive, but they also have some brilliant features that make them completely serviceable. In particular, the design of the bushings is brilliant, they can be removed with a screwdriver and quickly replaced. To do this maintenance, you need the FAA122 tool, which you can see in the photos. Considering the FAA122 is plastic, I immediately saw the possibility of printing one, and at that point, turning it into a socket seemed like the obvious way to go.

The torque spec on the socket is only 10 Nm, and with so many points of engagement on the splines, this tool can handle that easily. I could probably even print it with a 3/8" socket drive and not have issues, but the 1/2" is stronger as it spreads the drive forces over a larger radius, thus reducing the stress on the socket.

Thanks to Jon Wells of Envelo for his help in this project!

Thanks also to jaybeckr for modifying this to work as an FAA086 replacement as well - I've included his STL.

Fusion 360 F3D file included if you want to change anything.

Print Settings

Printer Brand: Prusa

Printer: i3 MK3

Rafts: No

Supports: No

Resolution: 0.2mm

Infill: 33%

Filament: Prusa PLA silver
Notes:

Printed in PLA as it's an easy print and is plenty strong enough. Could print in ABS or PETG if you'll keep it in a hot car or anywhere temps might get high.

I printed with 5 shells and a 33% infill, it could probably be printed even lighter and still work just fine.

No support needed, print as-is. No vertical detail, could print at any layer height you choose.