Seat clamp is used to secure the seatpost when inserted into the bicycle frame. It comes with different diameter as each bicycle seat tube varies in its diameter. It is important to note that the internal diameter of the seat clamp must be similar to the external diameter of the seat tube. Common sizes of seat clamp are 28.6mm, 31.8mm and 34.9mm.
There are two types of seat clamps:
- Quick Release Seat Clamp (Tightened using lever)
- Allen Key Seat Clamp (Tightened using allen key)
The tightness of the seat clamp is important for safety concern.
- Too loose will cause the seatpost to move and slide downwards
- Too tight will cause the seatpost clamp area on the frame to crack
Things to take note to ensure the proper usage of seat clamp:
- Minimum insertion depth of 8cm on seatpost is needed before the seat clamp can be tightened safely
- Seat clamp to be placed in line with the seat tube of bicycle frame
- Maximum torque is often written near the seat clamp area
A quick release seat clamp is particularly useful if you share your bicycle with family members of different height or for children as they are grow up fast.
You can check out Decathlon’s bicycle accessories, they carry the three seat clamp sizes as mentioned in my article.
If your seat post is too short and does not meet the minimum insertion length of 8cm to allow it to be tightened safely, do consider upgrading to a longer seat post, also available on Decathlon.
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