1/4" Drive Torx Bit

Torx-recessed fasteners earn their place in cycling because the six-pointed star recess delivers more grip area than hex at the same fastener size. That matters most where the bolt head is small and the torque is high: rotor bolts (M5 head, 4–6 Nm), some crank-arm bolts, headset top caps on modern integrated systems. A Torx bit that meets spec doesn't cam out under torque; a cheap one does.

The 187/2TX bits are the 1/4-drive Torx tips sized to bike-shop work, paired to any 1/4-drive ratchet or torque wrench.

Why Torx matters on bikes

Rotor bolts moved to Torx because the M5 head doesn't have enough material for a deep hex recess without weakening the bolt. The six-pointed star recess uses more of the available head material for the engagement surface, which means more torque before cam-out and less chance of stripping the recess on installation.

The standard Torx sizes in modern cycling:

• T10: small accessory fasteners
• T15: some shifter and brake-lever clamp bolts
• T20: modern stem caps, some brake-caliper bolts
• T25: the rotor-bolt standard; most disc-brake systems
• T27: some cleat bolts, some crank-bolt designs
• T30: some crank-arm bolts, especially Shimano Hollowtech II generations

T25 is the most-cycled Torx size in a bike shop. A worn T25 bit will round the rotor-bolt recess; replace it the moment it shows tip rounding.

Pairing with the torque wrench

For rotor bolts running 4–6 Nm, the 2-24 Nm Slipper Torque Wrench is the right driver, with this bit set providing the Torx tips. Torx fasteners need a calibrated torque wrench more than hex fasteners do, because the higher grip area lets you over-torque before you feel the resistance change at the wrench; the bit doesn't cam out to warn you. The torque wrench's audible click and slip-release replaces that warning.

When to step up to TX Plus

For higher-torque fasteners (crank-arm bolts running 50+ Nm with Torx heads), the TX Plus profile 1/2-drive socket is the better tool. TX Plus adds a small additional engagement surface inside the standard Torx recess, giving extra grip at the top of the torque range. For routine rotor-bolt work, standard Torx is fine; for high-torque applications, TX Plus.

Specs

• Drive size: 1/4 inch square
• Bit tip: tool steel, anti-corrosive finish
• Socket body: chrome-vanadium steel, hardened and tempered
• Dimensional standard: DIN 7422 (Torx geometry per industry spec)

Made in Slovenia, since 1919

Unior has been forging hand tools in Zreče since 1919, and is the official technical partner of multiple World Tour and downhill teams. Torx geometry is unforgiving of dimensional drift: a tip that's a few hundredths off-spec will round either the bit or the fastener recess on the first cycle. The DIN-spec dimensional tolerances on this bit set are what keep the cycle count high; the tool-steel tip is what keeps the geometry from wearing back into spec drift over time.

Pro tip from our mechanics

Replace your T25 bit the moment you see any rounding at the tip. A worn T25 will round an entire shop's worth of rotor bolts before you notice. For the broader bit and socket framework: Sockets and bits for bike work →.