The "Frame Swap" Unauthorized 33rpm is complete!

The UnAuthorized 33rpm, which was requested for a rebuild from an existing hardtail, is now complete.

The customer considered both the 45rpm and 33rpm, but ultimately chose the 33rpm because they preferred the frame's aesthetics. The size is XS.

Rebuild Highlights

This 33rpm features a 140mm travel specification.
While the 33rpm is originally designed for downhill prowess with 160mm travel, using a 20mm shorter 140mm travel is expected to overcome its weakness in climbing. The stack height is lowered, creating a well-balanced setup that should improve climbing ability and maneuverability.

The headset and bottom bracket, which could not be reused due to different standards, were replaced with components from UK-based HOPE.


These parts are highly recommended for their precision, rigidity, and excellent maintainability, ensuring long-term use.

About the Chrome Plated Specification

Only 40 units of the chrome-plated 33rpm, which is now complete, were produced. Manufacturer stock is already sold out.
Currently, Grumpy has only one S-size unit left in stock.
There are also a small number of chrome-plated 45rpm (S size) frames available, so if you're interested, please act quickly.

We look forward to hearing from you!

Feel free to consult us about rebuilds and advice.

"I want to transfer parts from my current frame."
"I don't know whether the 33rpm or 45rpm is right for me."
If you have questions like these, please feel free to consult us. We can show you actual build examples and discuss sizing at our store.

UnAuthorized chromoly frames are meticulously designed with deep involvement from active riders.
If you want to experience the fun of a hardtail, please consider these frames.