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Full Speed Ahead K-Force Stem



Impressively stiff stem but it's not the lightest and it's far from a cheap investment

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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The FSA K-Force Light stem, isn't the lightest, especially considering the hefty price, but it is incredibly stiff, making it perfect for powerful cyclists and sprinters.

The stem gets the high price on account of the fact it is entirely made from unidirectional carbon fibre. That helps keep the weight down despite its impressive girth. At the front it features a reverse carbon covered aluminum faceplate - they've removed the metal inserts from the stem body and located them in the faceplate.They've also removed metal threads from the steerer clamp too, and instead the Allen bolts thread into opposing bolts, requiring two Allen tools to tighten them up. All the bolts are titanium to further keep the weight down.

It weighs 172g. FSA's own SL-K stem is only a smidgen heavier and a heck of a lot cheaper. However, it's clear from the massive size of the K-Force Light that producing the lightest stem wasn't a key design criterion. Instead, the stiffness of the stem is impressive especially when compared to several other regular, and spindly in comparison, stems I compared it to. It reminds me of the Cavendish Pro signature stem and Zipp SL Sprint stem, also designed for Mark Cavendish, and it's obvious that's the sort of stem they're trying to offer here.

The steerer clamp is a 1 1/4in size, using a slim collar to space it out to fit a regular 1 1/8in stem. This means it'll fit a Giant with its OverDrive 2 setup or a Canyon, two of the big players using the oversized steerer tube at the moment. This small measure does future-proof the stem against any frame and fork upgrades, and in case any other manufacturers also adopt the larger tapered steerer tube size.

Fitting the stem is a bit more involving than a regular stem. The bolts securing the faceplate into position aren't as easily accessed and you'll struggle with a typical multi tool. A longer ball-ended Allen tool is preferable. Likewise for the steerer clamp bolts, you'll need a pair of Allen tools to tighten them up.

Testing the stiffness of a stem in the real-world isn't filled with accuracy, but it was clear that my bike with the K-Force stem fitted produced a stiffer feeling front end. I've been using it in a range of situations and it's in racing with the frequent out of the saddle accelerations and sudden changes of direction that the stem makes a difference. Admittedly it's a small difference, but it is noticeable - there's less flex at the ends of the drops when you're heaving heavily on them. That will be more important to some cyclists. If you're racing such a benefit is appreciated, but at the high price of this stem you might decide it's too costly a benefit.

The aesthetics of a stem are also important, as they are with handlebars and the seatpost. Many cyclists will readily admit to buying these components based purely on how they look over any weight or supposed performance gains, and critically how they look on their bike. The K-Force Light stem is a chunky piece of kit and didn't look too out of sorts on the Supersix Evo it was tested on, but on anything with skinnier tubes it could look a bit top heavy. It certainly won't satisfy all aesthetic preferences.

If you're a big powerful cyclist and want a stiff, yet light, stem, or a racer with sprinting as your trump card, the K-Force is well worth a look. For most cyclists there are more affordable stems that function just as well.

The K-Force Light is available in 100, 110, 120 and 130mm lengths with a 40mm fork clamp stack height in unidirectional carbon finish with a choice of red or black graphics.


Impressively stiff stem but it's not the lightest and it's far from a cheap investment test report

Make and model: Full Speed Ahead K-Force Stem

Size tested: 120mm

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?

Designed for the ultimate combination of lightweight, style, and performance the K-Force Light stem removes all alloy or steel components from stem body. K-Force Light features the latest in carbon fibre technology and is the choice of the top Pro Tour teams who count on their components to make their living.

Tell us some more about the technical aspects of the product?


* Monocoque Carbon body

* Carbon faceplate

* Titanium hardware


* - 6° x L100, 110,120, 130mm

* Ø31.8mm fork clamp diameter

(Ø28.6mm with included shim)

* Ø31.8mm handlebar clamp diameter

* 40mm fork clamp stack height

* Shim to adapt 1-1/4' stem to 1-1/8' steer tube



* UD Carbon finish

* Color graphics options - Red, Black


* 160 grams (100mm)

Rate the product for quality of construction:
Rate the product for performance:

If you want a stiff front-end the K-Force Light is impressive, without a weight penalty.

Rate the product for weight, if applicable:

It's not heavy as such, nor is it the lightest stem on the market. Considering its stiffness though, the low weight is impressive.

Rate the product for comfort, if applicable:
Rate the product for value:

Value for money goes out the window when you're looking at high-end products like this. It's clear you can pay a lot less and get a stem that is the same weight, lighter even, but the trump card of this stem is the high level of stiffness at a competitive weight.

Tell us what you particularly liked about the product

The stiffness, great for racing and hard riding.

Tell us what you particularly disliked about the product

All things considered, it's jolly expensive.

Did you enjoy using the product? Yes.

Would you consider buying the product? Not at this price.

Would you recommend the product to a friend? A racer/sprinter friend, yes.

Overall rating: 7/10

About the tester

Age: 31  Height: 180  Weight: 67

I usually ride:   My best bike is:

I've been riding for: 10-20 years  I ride: Every day  I would class myself as: Expert

I regularly do the following types of riding: road racing, time trialling, cyclo cross, commuting, touring, mtb,


David worked on the tech team from 2012-2020. Previously he was editor of and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds, and you can now find him over on his own YouTube channel David Arthur - Just Ride Bikes

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notfastenough | 10 years ago

Ooh, black red and white. Such an original colour scheme. Honestly, manufacturers should be banned from using these three in combination. Sure, if they're your thing you can buy pretty much anything to match, from frame to finishing kit, from helmet to shoes and anything in between, but it's just so so boring!

And if I had the cash to drop £250 on a stem, you can be sure I'd not want my bike to look the same as everyone else's.

/rant over.

Nick T | 10 years ago

I wouldn't be surprised at all if any of that theoretical stiffness is lost once you put a shim in the clamp. It looks the part though, I'm sure there's a place in the market somewhere for heavy and expensive pure carbon stems and not the carbon wrapped alloy compromises that seem more popular with manufacturers.

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