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Used by the pros, the FSA K-Force Light Seatpost SB0 is stiff, light and it looks stunning. The two bolt clamp holds the saddle firm, but it's fiddly to set up and the front bolt has design issues. There are length, diameter and setback options for everyone, but it's expensive against competition that's often lighter too.
If you've got the cash, and want to treat your Sunday best to a lovely upgrade, FSA's latest carbon post might just be the ticket. Featuring a one-piece carbon fibre construction, a forged alloy two-bolt 'Minimal Top Clamp,' and weighing in at 205g for the 31.6mm x 350mm version, it's a pretty slick bit of kit.
If pro teams including EF Education First Pro Cycling and BH Burgos, it must be good, right?
Well, mostly. The K-Force Light comes in zero offset (as tested) or 25mm setback, as well as 350mm or 400mm lengths. It works with either standard 7mm rails or 7x9mm oval rails. You also get a Di2 battery mount, if you're into the electronic wizardry, and FSA doesn't stipulate a weight limit.
Included in the box is a small packet of carbon paste. Normally I steer clear of this stuff as I worry it might scratch the finish (I use Park Tool's ASC instead, which secures slippery carbon without any abrasives), but in the interests of science I gave a go. The good news is it definitely works, and I've had no slippage at all. The non-news is that I haven't yet dared check for scratches.
Fit the saddle though, and things get tricky. The two bolt design is effective once tightened, but boy is it a pain to get the saddle on. Getting the two-piece clamp around the rails and then tightening the bolts successfully is the sort of thing that makes you think having several extra, child-sized hands growing from your chest would be worth the stares.
Next you find the angle of the front bolt forces any regular hex key into contact with the post – and tightening the bolt will mark the post. A ball-ended key will let you get so far, but when you need to properly torque it up, you can't do so without damaging it.
Possibly a very long T-handled, ball-ended hex driver would give you enough clearance and torque. Lacking one, I used a thin piece of card as a basic shield.
The two bolts do at least make angle adjustment super easy, so that's something, and it's entirely secure too.
The K-Force Light doesn't feel any more plush than my normal carbon post which was merely OK anyway (plus cheaper and lighter), but then a 31.6mm post is never going to have the compliance of a 27.2mm. You could also argue that, as something used by pro teams, comfort is secondary to stiffness.
Despite the 'Light' in the name the K-Force feels very substantial, and I feel confident it won't flex (or break) when I really mash the pedals – and I'm a pretty big rider.
The glossy finish looks rather posh, and thankfully there are no shouty logos to spoil things, but the style might not be for everyone. I prefer my finishing kit matt black, for instance.
£194.95 is a lot of money for a seat post, and I don't feel the K-Force Light is doing quite enough to justify it. At 206g it's light, sure, but there are lighter posts out there for similar money, such as the 163g Ritchey WCS Carbon Link Flexlogic at £187 or Prime's 190g Primavera Inline Carbon Seatpost at £129.99. I do think the FSA offers more for your money than the £215, 209g Vision Metron SB20 Seatpost, though.
The K-Force Light is beautifully made and looks fantastic, but weight, price and performance are all average or even lacking against the competition. There's no ignoring that problematic clamp, either. Admittedly, it works really well once together and tight, but getting there is a potentially damaging faff. Maybe the pros don't care because they're not the ones paying for it, and they're not having to fit the things either...
Light and beautifully made, but clamp design needs refining – and it's expensive
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road.cc test report
Make and model: FSA K-Force Light Seatpost SB0
Size tested: 31.6mm / 350mm
Tell us what the product is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
FSA says: "With shaft and head formed from one continuous carbon fiber section, the K-Force Light SB0 seatpost is both light and strong. The K-Force Light SB0 features a zero-offset (in-line) clamp for a forward saddle position, with our forged alloy Minimal Top Clamp holding the saddle securely."
Tell us some more about the technical aspects of the product?
Forged alloy Minimal Top Clamp (MTC)
One piece continuous carbon fiber construction
Fits 7mm standard rails and 7X9mm oval rails
Finish: UD carbon finish
Color graphics - black
Weight - 185 grams (Ø27.2x350mm)
0mm or 25mm setback
27.2 or 31.6mm width
350 or 400mm length
Feels incredibly well built and looks stunning.
Saddle attachment is fiddly, but the clamp is secure and the included carbon paste ensures the post never slips.
The glossy finish should help protect the carbon from marks.
Definitely not the lightest for the money, but pretty competitive.
It does damp some vibes, but as this it's designed for racing its primary purpose is to be stiff.
There are cheaper posts that do more or less the same job.
Tell us how the product performed overall when used for its designed purpose
Tell us what you particularly liked about the product
The looks and effective clamp.
Tell us what you particularly disliked about the product
Front bolt is almost impossible to tighten without marking the post.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
The Ritchey WCS Carbon Flexlogic is lighter for the same sort of money. Prime's Primavera Inline Carbon Seatpost costs £55 less and weighs roughly the same. It's cheaper than the high-performing, but heavy, Vision Metron SB20 Seatpost.
Did you enjoy using the product? Yes
Would you consider buying the product? No
Would you recommend the product to a friend? No
Use this box to explain your overall score
It's reasonably comfortable, stiff and fairly light, while the clamping is secure - all the things you want from a seatpost, really. It's exceptionally well built but the design makes it hard to tighten the front bolt without marking the post, which is a shame – especially given the price. Overall it's merely good, and a seven.
About the tester
I usually ride: Steel audax bike My best bike is:
I've been riding for: 10-20 years I ride: Every day I would class myself as: Experienced
I regularly do the following types of riding: commuting, touring, club rides, sportives,