Choosing between a 24mm, 30mm, or DUB spindle can significantly impact crankset performance. The 30mm spindle, found in many high-end models like QO and ROTOR, offers excellent stiffness-to-weight ratio. The 24mm spindle, popularized by Shimano, is known for reliability and long-term durability.
SRAM’s DUB spindle attempts to combine both advantages—30mm stiffness with a more robust sealing and interface system. For cyclists, spindle diameter affects frame compatibility, bearing wear, and even pedaling feel.
When choosing a crankset for performance cycling, the spindle diameter is one of the most underrated yet critical factors. While often overlooked compared to crankarm length or chainring type, the spindle size directly impacts stiffness, weight, bearing life, and frame compatibility. The three primary standards dominating the market are 24mm, 30mm, and DUB.
24mm: Proven Durability
The 24mm spindle—pioneered by Shimano and found in their Hollowtech II cranks—is a staple in the cycling world. Its appeal lies in long-term reliability and wide compatibility with bottom brackets. Many bikes are still designed around this standard, especially in endurance and touring categories.
Its steel construction makes it heavier than 30mm alternatives but contributes to its robust bearing interface, which tends to resist contamination and wear. Riders who prioritize low maintenance and proven reliability often gravitate toward this size.
However, for high-performance applications where grams and stiffness matter, the 24mm can be a limiting factor—especially in sprinting and aggressive climbing scenarios where flex becomes noticeable.
30mm: Stiffness and Performance
The 30mm spindle—widely adopted by high-performance brands like QO, ROTOR, Race Face, and Easton—was designed to improve the stiffness-to-weight ratio of cranksets. Often made of aluminum, 30mm spindles allow engineers to create lighter crank arms with larger interfaces, improving both power transfer and durability.
At QO, for example, cranksets like the QO-RACE and QO-GRAVA use a 30mm aluminum spindle precisely for this reason—offering elite-level stiffness without adding weight. Similarly, ROTOR’s ALDHU and VEGAST cranks leverage the 30mm standard for modular setups with high torsional resistance.
The tradeoff? Bearing size and sealing. Because the outer diameter of most bottom brackets remains fixed, a larger spindle diameter means smaller bearings. This can lead to faster bearing wear, especially in poor weather conditions, unless high-quality seals are used.
DUB: Hybrid Efficiency
SRAM’s DUB (Durable Unified Bottom Bracket) system aims to unify the benefits of both standards: the durability of 24mm with the stiffness of 30mm. With a 28.99mm spindle, it allows for slightly larger bearings than 30mm systems and tighter integration with SRAM’s own bottom brackets and cranksets.
While DUB is mostly limited to SRAM-compatible drivetrains, it has gained traction for its simplicity and sealing, especially in MTB and gravel setups where contamination can be a concern.
However, DUB is not truly universal—you’ll still need DUB-specific bottom brackets and compatible frames, which may limit component flexibility in mixed-brand builds.
Which One is Right for You?
If you value ease of service, wide compatibility, and long-term reliability—24mm remains a strong contender. It’s still used in many Shimano and FSA cranksets and is ideal for recreational riders or commuters.
If your goals are max power transfer and light weight, 30mm is the performance winner. It’s found in QO, ROTOR, and other elite brands for a reason. Just be sure to use high-quality bottom brackets and seals.
If you’re already riding a SRAM setup or want a well-balanced system with easier BB installation, DUB may be the answer—especially in mixed-surface disciplines like gravel or enduro MTB.
Conclusion
In summary:
- 24mm = proven durability, ideal for all-weather riding, heavier.
- 30mm = best for stiffness and weight, ideal for racing setups.
- DUB = hybrid option with good sealing and compatibility in SRAM systems.
For cyclists pushing performance boundaries, understanding spindle size is essential. Whether you’re riding QO’s carbon cranksets or building a mixed drivetrain with ROTOR or SRAM, the right spindle can enhance every pedal stroke.