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Crank Brothers Cobalt 3: Seat post



Beautiful post scuppered by a silly clamp

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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Crank Brothers Cobalt 3 Seatpost is an elegant, lightweight alternative to common as muck carbon for powerful riders of semi/compact road/TT bikes. However, the sample's clamp was poorly conceived and exceeding fiddly to adjust-not what I'd expect on an £80 seat post.

Measuring a whopping 400mm long and available in the standard 27.2,30.9 and 31.6 diameters, the cobalt continues the brand's trademark flawless, almost fluid and undeniably seductive lines. It's fashioned from 7075 series aluminium which is in many respects ideal for finishing kit-especially lofty seatposts thanks to a superior strength to weight ratio. Detailing and accuracy of machining is pin sharp, our 27.2 slipped seamlessly inside the seat tube, snugged tight by the frames binder bolt in a matter of turns.

There's even a series of embossed dots designed so you can put a drop of paint to denote exact in-a-glance saddle height. Objectively a 10p cable tie will serve precisely the same purpose but then, to paraphrase Wilde, the cynic knows the price of everything and the value of nothing. Ours was the inline model designed to place the rider in a more aggressive, aerodynamic stance-perfect for time trial duties but there's also a version with twenty-degree layback (to counteract ultra steep frame angles while providing that extra bit of momentum on the climbs).

Despite the relative thin gauge tubing, ours has never felt remotely whippy-even with 300mm exposed. 70 kilos shouldn't overly stress fitting kit but provocatively lashing the tagalong aboard and heading for some very challenging descents it didn't flinch allowing me to concentrate on turning a steady, even cadence so, theoretically more powerfully built riders shouldn't have any problems. By the same token, it never felt like a pneumatic drill after two hours or so chasing through rutted lanes and trails. For all this, the cradle is a prime example of form over function being time consuming to set up and developing an unnerving habit of loosening mid ride- a real pain if your multi-tool hasn't a torx bit.


Beautiful post scuppered by a silly clamp.

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Make and model: Crankbrothers Cobalt 3: seatpost

Size tested: Cobalt 3 xc mtb seatpost - iron black

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?

"The Crank Brothers Cobalt 3 seatpost is constructed from strong 7075 aluminum alloy for exceptional strength with no weight penalty. Zero setback positions you forward over your bars for a more aerodynamic position".

7075 aluminum alloy is strong and lightweight

Zero setback for a more aerodynamic position

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

DIAMETER: 27.2mm, 30.9mm, 31.6mm

LENGTH: 400mm

MATERIAL: Aluminum


WEIGHT: 254g (31.6mm)

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

Clamp aside, it should prove a very reliable alternative to carbon.

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

Tell us how the product performed overall when used for its designed purpose

As a lightweight alternative to carbon, the cobalt 3 potentially has a lot to offer taller riders using smaller compact/mtb framesets thanks to strength, rigidity and high quality machining. However,the seat clamp proved frustrating to adjust and ours developed a disconcerting habit of loosening mid ride-not acceptable on a post nudging £80

Tell us what you particularly liked about the product

Slick design and quality of machining.

Tell us what you particularly disliked about the product

Clamp proved a major disappointment.

Did you enjoy using the product? Form very much presided over function.

Would you consider buying the product? Only with a redesigned clamp

Would you recommend the product to a friend? Not in its present guise

Overall rating: 6/10

About the tester

Age: 37  Height: 1m 81  Weight: 70 kilos

I usually ride: Rough Stuff Tourer Based around 4130 Univega mtb Frameset  My best bike is: 1955 Holdsworth Road Path and several others including cross & traditional road

I've been riding for: Over 20 years  I ride: Most days  I would class myself as: Experienced

I regularly do the following types of riding: cyclo cross, commuting, touring, fixed/singlespeed, mtb,

Shaun Audane is a freelance writer/product tester with over twenty-eight years riding experience, the last twelve (120,000 miles) spent putting bikes and kit through their paces for a variety of publications. Previous generations of his family worked at manufacturing's sharp end, thus Shaun can weld, has a sound understanding of frame building practice and a preference for steel or titanium framesets.
Citing Richard Ballantine and an Au pair as his earliest cycling influences, he is presently writing a cycling book with particular focus upon women, families and disabled audiences (Having been a registered care manager and coached children at Herne Hill Velodrome in earlier careers)

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