Kaisei Seat Tubes


Superlight seat tubes with different butt lengths for large and small frames. Heat-treated CrMo for ultimate strength and durability.

Made in Japan.


The performance of steel bikes has been perfected to such a degree that even today, steel is the material of choice for the bikes that take us on our adventures. Kaisei makes the best steel tubing in the world, widely respected for its consistent quality and perfect roundness. Long reserved for the track bikes of Japan’s Keirin professionals (who race on steel bikes), Rene Herse now offers Kaisei tubing in custom-drawn dimensions for modern allroad and randonneur bikes.

Click here to read more about Kaisei tubing and why even today, the best bikes are made from steel tubing.

  • Heat-treated CrMo
  • "Short" size: 610 mm, with shorter thin "bellies" and longer butted ends, for small frames and where extra strength for front derailleur braze-ons is desired
  • "Long" size: 650 mm, with longer thin "bellies" and shorter butted ends, for large superlight frames