Your next weight saving is at the heart of your bike. Darimo Sigma carbon cranks start at just 240g for both arms, spindle, fixing bolt and preload adjuster. Handmade in Spain for road, gravel and MTB, they bring Darimo’s obsessive carbon engineering to your drivetrain.
Take your build lighter: crank assemblies from just 240g
Keep power measurement: accepts compatible 8-bolt spider-based power meters
Preserve your preferred fit: five lengths, with mixed arm lengths at no extra cost
Get extra support without extra cost: free reinforcement for heavier riders or greater stiffness
A build you’ll be proud to pick up
There’s satisfaction in lifting your bike and knowing where the weight has gone. Sigma brings that attention to the centre of your build, with hollow carbon arms, a hollow carbon spindle and six finishes to make it your own.
The left arm and spindle are laminated as one continuous carbon piece. There is no bonded joint between them: the fibres run directly from the spindle into the arm to carry the pedalling loads.
Each crank length has its own optimised laminate, combining unidirectional and braided carbon. Sigma exceeds ISO 4210 test requirements, backing its exceptionally low weight with structural testing.
Your drivetrain. With more Darimo.
The 8-bolt direct-mount interface supports single and double chainring setups using direct-mount rings or an 8-bolt spider. It also accepts compatible spider-based power meters, so a lightweight build can still have the training data you rely on.
Four spindle configurations accommodate road, gravel and mountain bike frames, with Q-factor starting at 148mm. A fine preload adjuster sets bearing preload for smooth rotation without lateral play.
Featured on a Dangerholm custom build
Gustav Gullholm, known as Dangerholm, is a custom bike builder recognised for extreme lightweight projects. Sigma cranks featured on his custom Scott Scale RC SL gravel build.
See the Sigma-equipped Scott in BikeRumor’s coverage.
Specifications
Design: One-piece left arm and spindle, without a bonded joint
Spindle diameter: 28.99mm, DUB-compatible
Crank lengths: 155, 160, 165, 170 and 172.5mm
Mixed arm lengths: Available at no extra cost
Interface: 8-bolt direct mount for single or double chainring setups
Preload: Millimetric preload adjuster
Standard rider weight limit: 90kg, with free reinforcement available
Testing: Exceeds ISO 4210 requirements
Finishes: 3K Gloss, 3K Matte, UD Gloss, UD Matte, Forged Gloss and Forged Matte
Manufacture: Handmade in Llíria, Valencia, Spain
Spindle options
Road: 240g
148mm Q-factor · 44.75mm chainline
Road-Wide / Gravel: 240g
153mm Q-factor · 47.25mm chainline
MTB: 260g
163mm Q-factor · 51.5mm chainline
MTB Wide: 260g
169mm Q-factor · 54.5mm chainline
Published weights use 165mm arms and include spindle, fixing bolt and preload adjuster. Excludes chainrings, spider or power meter, and bottom bracket.
Chainlines shown use a 6.5mm-offset chainring for Road/Road-Wide and a 3mm-offset chainring for MTB versions. Chainline varies with chainring offset. Q-factor is the width between the outer faces of the crank arms at the pedal threads.
Darimo does not apply clear coat or varnish. Small surface voids can be visible as part of the carbon manufacturing finish.
FAQs
How much weight will I save?
Road and Road-Wide versions weigh 240g with 165mm arms. MTB versions weigh 260g. Compare that with your existing arms, spindle and fixing hardware to calculate the saving. Chainrings, power meter and bottom bracket are accounted for separately.
Can I use Sigma with Shimano or SRAM gears?
Yes. You can retain your Shimano or SRAM gears and configure Sigma with chainrings selected for that drivetrain. The 8-bolt mounting interface supports both single and double chainring setups.
Can I use my existing chainrings or power meter?
Sigma accepts 8-bolt direct-mount single chainrings, 8-bolt spiders and compatible spider-based power meters. Existing chainrings can be retained when they fit a suitable 8-bolt spider and match the drivetrain. Shimano chainrings do not attach directly to the Sigma arm.
Will I need a different bottom bracket?
If your bike has a Shimano 24mm bottom bracket, it will need a DUB-compatible bottom bracket for Sigma’s 28.99mm spindle. This is a normal component replacement using a bottom bracket suited to your frame. If you already use DUB, a replacement may not be necessary.
Can I retain my current crank length?
Yes, if you currently use 155, 160, 165, 170 or 172.5mm cranks. Select the matching length to retain that part of your fit. Darimo also offers different left and right arm lengths at no extra cost for riders with a mixed-length fit prescription.
Can riders over 90kg use Sigma?
Yes. Darimo offers reinforcement at no extra cost for riders over the standard 90kg limit. Include your rider weight and reinforcement request in your order notes. Riders under 90kg can also request reinforcement for a stiffer version.
Less weight. More Darimo. Select your Sigma configuration and order above.