How to Keep a BMX Chain Tight

BMX style bicycles are made short and stout to withstand the incredible stresses placed on the frame. Unlike other bicycles, the BMX rear drop-outs -- where the wheel connects to the frame -- have the wheel placement directly behind the frame versus perpendicular to it. This gives the BMX frame added strength for the jumps and bumps associated with the sport. This also means there is no place for a derailleur, making it difficult to keep needed tension to the chain. Use a BMX chain tensioner to tighten and adjust the chain as needed. Failure to keep the chain tight results in the chain sliding off the drivetrain, which can lead to a dangerous situation.

Things You'll Need

  • BMX chain tensioner
  • Adjustable or cone wrench
  • Chain sag measuring tool
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Instructions

    • 1

      Flip the bike upside down and rest it on flat ground at the seat and handlebars. Pull the chain off the drivetrain and let it hang off the cranks. Unscrew the rear-wheel axle using an adjustable or cone wrench.

    • 2

      Insert the chain tensioner onto the axle on the right side of the rear wheel. Push the rear wheel back onto the drop-outs, with the tensioner resting in the axle. A chain tensioner looks like a large hexagonal-shaped nut.

    • 3

      Screw the axle and wheel back onto the bike. Thread the chain back over the drivetrain.

    • 4

      Push the chain up and down and use a chain tensioner measuring tool, which is available at bicycle shops. Check the chain sag, and then turn the tensioner nut with the adjustable tool. Turn it clockwise to tighten the chain.

    • 5

      Feel for slack and take the chain tension measurement with the measuring tool and make micro-adjustments with the tensioner until reaching the desired tightness on the chain.