Carbon Fiber Seatpost FAQ

Over the years lots of people have asked why Thomson does not produce a carbon fiber seatpost.

The short answer is that the technology does not exist at this time to make a carbon fiber seatpost that meets our requirements for strength, safety and failure mode.

For those interested in the details?

Original Goals of the Thomson Seatpost Design:

• Make the strongest post on the market.
• Make a post with the correct failure mode, bend-don’t break.
• Make a post with a long life cycle.
• Make a post that engages with the saddle and the seatube of the bike in a simple manner.
• Make a post that is light while being strong and safe.

While in initial design we pondered what material to make our post from. Steel and titanium have very nice characteristics but are heavy per volume and Ti is expensive. Aluminum offers strength and light weight, when anodized it is corrosion resistant and the alloy we chose has great fatigue life.

At Thomson we have a universal definition for strength. Strength is not just defined by the integrity of the individual part being tested. We design with mating parts in mind and have made many design decisions that enhance the over all experience of using our products by making sure that they safely integrate with other bicycle parts.

Bikes are used in rigorous ways in the outdoor environment. Bikes are prone to being scratched and dinged in their use. The strength of carbon fiber is vulnerable if it gets a surface scratch.

Hoop strength refers to a materials ability to resist damage when clamped. Carbon fiber is notoriously weak in this regard. We feel it illogical to use a material that is not made for being clamped around its circumference in a seatpost. Clamping forces can lead to fiber shearing and/or delamintaion of carbon fiber.

We designed the Thomson post to bend above the max line, bend-not break. We designed all of the clamping mechanism to be stronger than the post so that no matter what, the saddle stays with the post in a failure. We received a patent for this failure mode; we call it our bending fuse. Carbon fiber will not fail in this manner. Carbon can be strong but when it reaches failure point it fails catastrophically.

At Thomson we believe excellence is achieved in studying the details. We incorporated other things in our design such as longer saddle rail clamps to protect saddle rails. We have invested in better than industry standard anodize to prevent corrosion and to prevent posts freezing in frames. Our Masterpiece manufacturing process creates a post that is stronger and lighter than carbon.

A carbon post has to be built robustly enough to bend repeatedly without fatiguing. Thomson posts are tested in both design and production for strength and fatigue. The Elite and Masterpiece have fatigue lives double that of other available posts. If you make carbon posts strong enough to offer good fatigue life, again they will be heavier than aluminum posts

At this time we see no reason to switch to carbon fiber, and many reasons to stay with aluminum. Aluminum most importantly makes a much safer seatpost. The market backs our product, its quality and the material it is made from. For people whose first concern is weight, our Masterpiece seatpost is the solution. After 9 years, if we had it to do all over again the Thomson seatpost would still be aluminum.