How to Change the Front Gears for a BMX

Competitive BMX racers are often faced with the need to change the front gears on their bikes. Replacing the front sprocket can change the racing dynamic of your BMX bike by creating a different gear ratio. Larger front gears create taller gearing, allowing for faster high-speed sprinting but slower accelerations. Smaller front gears make it easier to accelerate from a stop, but limit the top-end speed you can achieve on your BMX bike.

Things You'll Need

  • 6mm Allen wrench
  • 8mm Allen wrench
  • Rag
  • Anti-seize
  • Chain lube
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Instructions

    • 1

      Locate and loosen the pinch bolts from the right crank arm. The pinch bolts are the bolts that hold the crank arm onto the bottom bracket spindle. Most pinch bolts can be loosened with a 6mm Allen wrench, but a small number require a different size of Allen wrench.

    • 2

      Remove the sprocket bolt; this is the bolt that attaches the chain ring to the crank arm, and its head can be located on the interior side of the sprocket. The sprocket bolt is usually removable with a 6mm Allen wrench.

    • 3

      Use an 8mm Allen wrench or crank arm puller to remove the spindle bolt; this is the bolt in the middle of the front chain ring.

    • 4

      Pull the crank arm away from the bike.

    • 5

      Remove the front sprocket from the spindle, allowing the chain to rest on the bike's frame.

    • 6

      Slide your new sprocket onto the spindle, and pull the chain onto the sprocket's teeth.

    • 7

      Slide your crank arm back onto the spindle.

    • 8

      Secure the sprocket onto the crank arm by tightening the sprocket bolt. Ensure that it is fully tightened and that there is no play between the sprocket and the crank arm.

    • 9

      Tighten the spindle bolt down, securing the crank arm and sprocket assembly onto the bottom bracket.

    • 10

      Screw down the crank arm's pinch bolts. Alternate between tightening the two, ensuring that pressure is evenly applied to the crank arm.

    • 11

      Apply chain lube to your chain, allowing for the new sprocket to gel better with your existing drive line components.