How to Tighten a BMX Bike Chain


To help transmit power into motion with optimal efficiency, a bicycle chain must be properly adjusted. A chain that is too tight can cause the drive train to bind, and one that is too loose can slip off the front chain ring, resulting in a sudden and dangerous loss of pedaling resistance (References, No. 1). Chain tension on single-speed bikes, such as BMX bikes, is regulated by moving the rear axle along the fork end. Establishing ideal chain tension allows the cranks to turn efficiently and prevents potential accidents caused by sudden chain slippage.

Things You'll Need

  • Socket wrench and socket (or adjustable wrench)
  • Bike work stand (optional)
  • Elevate the rear wheel of the bike by placing the bike in a work stand or by turning it over so that it’s resting on its seat and handlebars.

  • Use a proper size socket and socket wrench or adjustable wrench, and turn each of the rear axle nuts counterclockwise. The nuts are located on both ends of the axle. You do not need to remove the nuts, only loosen them.

  • Slide the wheel (now that the axle nuts are loose) toward the rear of the bike. This will in turn tighten the chain, which is attached to the wheel by way of the drive sprocket.

  • Check the chain for proper tension. Grab the chain midway along the chainstay (the lower portion of frame that parallels the chain) and wriggle it up and down. Ideally there should no more than a half-inch of play (see References, No. 2). Continue to move the wheel back if necessary, and re-check the tension.

  • Re-tighten each of the axle nuts, securing the wheel and chain in place.

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  • Photo Credit bmx weels image by Alexey Klementiev from
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