Aluminum Bottom Bracket Socket FSA MegaEvo

FSA's MegaEvo is the company's external bottom bracket cup that sits in the 16-notch HT2-compatible family. A 24 mm Shimano-pattern spindle, an outer engagement that follows the broader 16-notch standard, and Cinch-system cranks that thread into it.

The 1671 Aluminum BB Socket cut for FSA MegaEvo is sized specifically to the MegaEvo cup's outer profile. The splines mesh across the engagement; the aluminum body matches the cup's hardness so there's no metallic scarring after multiple service cycles. For shops that mainly see Shimano-equipped builds, the BBR60 or 16-notch generic socket covers most jobs; the FSA-specific socket is the right call when a workshop services FSA-equipped frames regularly enough that the cup's specific fit matters.

Compatibility

• FSA MegaEvo external bottom brackets (24 mm spindle, Shimano-compatible)
• FSA Cinch-system BBs where the outer cup follows the MegaEvo notch profile
• Not for 30 mm-spindle FSA cups; those use a different socket pattern in the line

Specs

• Drive: 1/2" square drive (use with a torque wrench, ratchet, or fixed handle such as the Pro Socket Handle)
• Material: CNC-machined aluminum, red-anodized
• Notch fit: FSA MegaEvo outer profile
• Includes: the socket itself; pair with the Bottom Bracket Socket Retaining Tool when servicing low-profile cups

Built in Zreče

Unior has been forging hand tools in Zreče since 1919, and is the official technical partner of multiple World Tour and downhill teams. The MegaEvo socket exists because FSA's cup geometry differs from Shimano's by enough to round a generic wrench's notches over a few service cycles; a cut sized to FSA's specific profile is what keeps both the socket and the cup serviceable past the first install.

Pro tip from our mechanics

FSA cups thread the same direction as Shimano-pattern BSA: drive-side reverse-threaded, non-drive normally threaded. The direction sticks for most mechanics; what catches people out on FSA is the install torque. FSA publishes a tighter band than Shimano's 35–50 Nm range on current MegaEvo cups, so verify the current FSA service documentation before applying torque, especially on carbon shells where the frame manufacturer may specify a value lower than FSA's recommendation.

For the BB install procedure and thread-direction reference: Replace or clean your bottom bracket →.