Seatpost clamping on carbon bike frames
Correct installation of a seatpost
Tolerance in diameter seatpost to seat tube
Carbon is a very high-performance material, it is not for nothing that high-tech sports equipment is made out of it. However, this material is very sensitive to pressure and clamping forces. If components are fixed together by clamping, as with a seatpost, tolerances and tightening torques for fits must be maintained exactly.
A round seatpost should be very full or with a maximum of 0.2 mm clearance to be introduced. This tight tolerance ensures that the carbon material, the end of the seat tube in general, is not under unnecessary preload to clamping / fixing the seatpost in its position. In that case the material has to bridge a very small "path" to the terminal contact.
This has a very reducing effect on the carbon structure during use and prevents classic crack formation in the clamping area. Unfortunately, no such recommendation is to be given for aero seatposts, as this is then an individual construction of the manufacturer and therefore it depends exclusively on the specifications of the manufacturer.
Seatpost - Guided minimum length in the seat tube
Another very important aspect in the clamping of a seatpost is the guided length in the seat tube. A good orientation size is a guided length about 2-3 cm below the lower edge of the top tube. By a too short guided seatpost all forces of the saddle / seat post are introduced to a very small area / section, the end of the seat tube in the frame and it so often leads to an overload of the local structure and destruction in the form of tears. Therefore, never mount a seat post too short in the seat tube.
The use of carbon mounting paste should here be common practice. With the carbon mounting paste, the forces can be reduced by up to 30%, which protects the pressure-sensitive carbon structure sustainably and protects against damage and wear in use.
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