What size Cranks do I need?

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The correct BMX crank arm length is crucial for performance, comfort, and injury prevention. Here's a breakdown of why it's important and how it impacts your riding:


🔧 1. Power and Leverage

• Longer crank arms (e.g., 175mm+) give you more leverage, which can help with:
  
  
  
  • Explosive starts in racing.
    
    
    
    
• Shorter crank arms (e.g., 165mm or shorter) reduce leverage slightly but:
  
  
  
  • Allow for faster, more efficient pedaling.
    
    
    
  • Can help spinners or tech riders keep tighter control.
    

🦵 2. Rider Size and Leg Length

• Crank length should be somewhat proportional to leg length.
  
  
  
  • Taller riders generally benefit from 170–175mm.
    
    
    
  • Shorter riders or younger riders might prefer 160–165mm.
    
    
    
• A mismatch (too long or too short) can cause:
  
  
  
  • Knee pain.
    
    
    
  • Awkward pedaling motion.
    
    
    
  • Decreased efficiency or trick execution.
    
    

✅ 5. Comfort and Knee Health

• Proper crank length helps maintain a natural pedal stroke.
  
  
  
• Improper length can lead to:
  
  
  
  • Overextension or compression of the knees.
    
    
    
  • Long-term joint issues, especially with aggressive riding.
    
    

💡 Summary ChartRider Height
Suggested Crank Length

Under 5’5” (165cm)
160–165mm

5’6”–6’0” (167–183cm)
165–175mm

Over 6’0” (183cm)
175–180mm


📌 Final Tip:Crank length also affects bottom bracket height and bike geometry, so it's worth testing different lengths if you're upgrading or customizing your BMX setup.