How to tighten bike chain

If the chain on your single speed or hub gear bike keeps falling off or if it feels loose then it may need to be tightened. The chain gets loose over time because it wears and stretches. In this guide we explain how to tighten bike chain correctly. 

The bike chain can only be tightened if it doesn’t have the derailleur. If the chain on your derailleur is loose or slipping then that is a different problem.

How to tighten bike chain- preparation

• If you have a BMX or a child’s bike, you will need to make sure that the saddle is high enough to lift the rear wheel off the floor when the bike is turned upside down.

• If necessary move any fittings on the handlebars such as bells and reflectors so that they don’t get damaged.

• Put some cardboard or cloths on the floor to protect the saddle and bars and turn the bike upside down.

• Make sure that the chain is on the teeth of the chainset and the rear sprocket.

• Loosen the wheel nuts. 

• Some bikes with no derailleur have a brake that attaches to the chainstay. It is important to release this before you attempt to move the wheel as the task can’t be performed while the brake is attached. If you have a roller or coaster brake, undo and remove the bolt that holds the brake arm onto the chain stay. 

How to tighten bike chain

• Stand in front of the rear wheel on the non-drive side.

• With your left hand push the wheel against the right hand chain stay, pushing the axle back into the dropout. 

• While still holding the wheel in position use your right hand to tighten the right hand wheel nut.

• Release the wheel and it will spring towards the centre but won’t necessarily be exactly in the middle. 

• Now stand behind the rear wheel on the drive side.

• With your left hand push the wheel across to the left side until it sits centrally in the frame. 

• Using your right hand, tighten the left hand wheel nut.

• Turn the cranks and check the chain. If it is too loose or too tight then repeat the process until you are happy. If you don’t tighten it enough then it may come off while you’re riding and if you overstretch the chain it might make a crunching sound and accelerate the wear on the chain and sprockets. 

• Because the chainset and sprocket are never perfectly concentric, there will be spots where the chain is loose and spots where the chain is tight.  If the loose spots don’t cause the chain to come off and the tight spots don’t cause the chain to bind, then the chain is the best tension that it can be. If the chain has a very tight spot then loosen the right hand wheel nut and gently push the wheel to the left, only 1 or 2 mm. The goal is to get the chain as even tension as possible while keeping the wheel central.  The best way to do this is to always keep one of the wheel nuts tight.
• When you are happy with the chain tension, give the wheel nuts a final check.

• If you have a roller or coaster brake, refit the brake arm to the chainstay.  

Chain tensioning bolts

These are sometimes called tug nuts and are often found on BMXs and single speeds with track ends. 

• Undo the wheel nuts.

• Start tightening the chain tensioning bolts alternately, a little at a time so that the wheel doesn’t move too far away from the central position.

• Tightening the bolts draws the wheel back and to the side you are adjusting. By swapping the sides as you tighten you will be able to achieve a well-tensioned chain and keep the wheel central.

• During the process, spin the wheel to check the chain tension.

• When you are satisfied, tighten the wheel nuts.

Turn the bike the right way up and reposition the stuff on the handlebars and lower the seat if necessary.