The winners in the vibration damping test, and the only ones under 0.6 G of acceleration, were the FSA K-Force Light SB25 carbon seatpost and the Specialized S-Works FACT Carbon post. It is unclear why the FSA was so effective at damping vibration, but perhaps the blocky carbon structure at the clamp is able to effectively soak up vibrations. The Specialized seatpost, originally made for the Roubaix road bike, is specifically designed to damp vibration. The active ingredient is an elastomer bumper pressed into the top of the post; based on this test, it does its job well.
Coming in a close third, at 0.616 G, was the Cane Creek Thudbuster/ST. We included this mountain-bike suspension post to see how it stacked up against more traditional designs. While it does perform well in the vibration test, one could get superior performance (especially over the kind of small bumps encountered regularly on the road) with a considerable weight savings by using the FSA or the Specialized post.
The poorest performer in this test, with more than twice the amount of Gs as the top three performers, was the Ritchey WCS carbon straight post. Second to last, and the only other post measuring over a full G of acceleration on these small, rapid impacts was the Thomson Masterpiece straight post.
How Seatpost Material Affects Vibration
The Ritchey WCS setback seatposts in carbon and aluminum share the same design and are both very lightweight relative to others in their class. When it comes to vibration damping, the carbon version outshines its aluminum cousin, albeit not by a huge margin—less than 0.1 G. Bottom Line: Carbon seatposts absorb road vibration better. Five of the top six posts in this test were carbon; the only aluminum post in the top six is built with pivots and an elastomer.
Damping: Setback vs. Straight
We set the saddle in the identical position (height, fore-aft, and tilt) with every seatpost. So that means that on straight seatposts, the saddle was shoved most of the way back on its rails, and on setback seatposts, the saddle was shoved most of the way forward on its rails. And we were measuring both variables (damping and flex) at the saddle, so the saddle plays a part in all of our tests, just as it does for you when you’re out riding. Our test showed that having the saddle pushed back on a straight seatpost resulted in the rider being bounced around more than on a setback seatpost with the saddle pushed forward.
With the Moots Cinch titanium posts and the Zipp Service Course SL aluminum posts, the performance difference between the straight seatpost and the setback version of the same model was minimal. The difference in vibration damping performance of the Ritchey WCS carbon seatposts was huge, however. The vibration passed on to the rider by the zero-setback Ritchey WCS carbon seatpost was nearly double that of its 25mm setback sibling. Bottom Line: Setback posts offer more vibration damping than straight posts; how much more will vary by manufacturer.
Damping: Seatposts with Suspension Features
The Specialized S-Works FACT Carbon seatpost almost won the overall test, with the Cane Creek Thudbuster/ST and Cannondale SAVE both coming in the top 1/3 overall. Bottom Line: Suspension can save your ass. Of the top five seatposts for vibration damping, three of them incorporate suspension designs.