text: Separate chain tensioning devices, such as the type that attaches to the dropout (commonly used on single speed mountain bikes) cannot be used because they are damaged as soon as the lower part of the chain becomes tight.
  Chainline
  Additional adjustments or modification may be needed to ensure a good chainline. The chain should run straight from the chainring to the sprocket, therefore both must be the same distance away from the bicycle's centerline. Matched groupsets of track components are normally designed to give a chainline of 42 mm, but conversions using road or mountain bike cranksets often use more chainline. Some hubs, such as White Industries' ENO, or the British Goldtec track hub, are better suited to this task as they have a chainline greater than standard. Failure to achieve good chainline, at best, leads to a noisy chain and increased wear, and at worst can throw the chain off the sprocket. This can result in rear wheel lockup and a wrecked frame if the chain falls between the rear sprocket and the spokes. Chainline can be adjusted in a number of ways, which may be used in combination with each other:
  Obtaining a bottom bracket with a different spindle length, to move the chainring inboard or outboard
  Choosing a bottom bracket with two lockrings, which gives fine adjustment of chainring position
  Respacing and redishing the rear wheel, where permitted by the hub design