Set A Limit Screw On A Rear Derailleur

Introduction

The rear derailleur moves the chain left and right so it engages different cogs on the back wheel. A spring pushes it in one direction - usually towards the high gears, the small cogs. A cable pulls it in the other direction.

Step 1

<h3>Step 1</h3><p>The limit screws restrict the movement of the derailleur so it can’t move the chain into a position where there is no cog. They are usually labelled with a tiny letter ‘H’ and a tiny letter ‘L’ for HIGH and LOW.
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Limit Screw

The limit screws restrict the movement of the derailleur so it can’t move the chain into a position where there is no cog. They are usually labelled with a tiny letter ‘H’ and a tiny letter ‘L’ for HIGH and LOW.

Step 2

<h3>Step 2</h3><p>Some people prefer to set a limit screw before the cable is connected, or with the cable demounted so it can’t pull. That means even if the cable breaks in use there is no risk of the chain shifting off the cogs, although this is an optional step.
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Demount Or Release The Cable

Some people prefer to set a limit screw before the cable is connected, or with the cable demounted so it can’t pull. That means even if the cable breaks in use there is no risk of the chain shifting off the cogs, although this is an optional step.

Step 3

<h3>Step 3</h3><p>With the back wheel off the ground stand behind the bike with your head on the centre line. Turn the ‘H’ limit screw until the top jockey wheel sits directly under the smallest cog. Clockwise pushes the derailleur left, anti-clockwise allows the spring to push the derailleur right.
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High Limit

With the back wheel off the ground stand behind the bike with your head on the centre line. Turn the ‘H’ limit screw until the top jockey wheel sits directly under the smallest cog. Clockwise pushes the derailleur left, anti-clockwise allows the spring to push the derailleur right.

Step 4

<h3>Step 4</h3><p>Pedal the bike gently, push against the rear derailleur to shift into a lower gear. When you release the derailleur the chain should drop back promptly on to the highest gear. Turn the pedals faster and let the chain drop suddenly to be certain it won’t move too far right and jump over the smallest cog and fall off. Turn the pedals backwards and the chain should run smoothly through the derailleur when the derailleur is in it’s default – highest gear – position.
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Check

Pedal the bike gently, push against the rear derailleur to shift into a lower gear. When you release the derailleur the chain should drop back promptly on to the highest gear. Turn the pedals faster and let the chain drop suddenly to be certain it won’t move too far right and jump over the smallest cog and fall off. Turn the pedals backwards and the chain should run smoothly through the derailleur when the derailleur is in it’s default – highest gear – position.

Step 5

<h3>Step 5</h3><p>If you need to make further adjustments move the limit screw a quarter turn at a time and check again after each adjustment. That way if you go too far you know how much to go back.
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Small Adjustments

If you need to make further adjustments move the limit screw a quarter turn at a time and check again after each adjustment. That way if you go too far you know how much to go back.

Step 6

<h3>Step 6</h3><p>Pedal the bike gently and push the derailleur towards the lowest gear position.
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Low Limit – Diagnose

Pedal the bike gently and push the derailleur towards the lowest gear position.

Step 7

<h3>Step 7</h3><p>If the chain won’t go into first gear – the biggest cog – you need to turn the ‘L’ limit screw anti-clockwise to allow it to move further. If the arm of the derailleur starts to rattle on the spokes or the chain goes over the biggest cog and falls off you need to turn the ‘L’ limit screw clockwise to limit the derailleur's range of movement. As you get closer to the target make small defined adjustments so if you go too far you know how much to go back.
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Adjust

If the chain won’t go into first gear – the biggest cog – you need to turn the ‘L’ limit screw anti-clockwise to allow it to move further. If the arm of the derailleur starts to rattle on the spokes or the chain goes over the biggest cog and falls off you need to turn the ‘L’ limit screw clockwise to limit the derailleur's range of movement. As you get closer to the target make small defined adjustments so if you go too far you know how much to go back.

Step 8

<h3>Step 8</h3><p>Once you have the right position for the ‘L’ limit screw double check by pushing the derailleur hard as you pedal to try and get the chain to fall off behind the first gear cog or the derailleur arm to hit the spokes.
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Check

Once you have the right position for the ‘L’ limit screw double check by pushing the derailleur hard as you pedal to try and get the chain to fall off behind the first gear cog or the derailleur arm to hit the spokes.

Step 9

<h3>Step 9</h3><p>Some bikes are equipped with a plastic disc between the first gear cog and the spokes, this is a ‘spoke protector’ sometimes called a ‘dustbin lid’ or a ‘pie plate’. If the ‘L’ limit screw is kept in the right place you don’t need it. It can be removed by taking off the cassette or freewheel and unclipping it from the spokes.
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Dustbin Lid

Some bikes are equipped with a plastic disc between the first gear cog and the spokes, this is a ‘spoke protector’ sometimes called a ‘dustbin lid’ or a ‘pie plate’. If the ‘L’ limit screw is kept in the right place you don’t need it. It can be removed by taking off the cassette or freewheel and unclipping it from the spokes.

Step 10

<h3>Step 10</h3><p>Some derailleur work in the opposite direction. The spring pushes towards the low gears and the cable pulls toward the high gears. If you have one of these the process is roughly the same. Start by positioning the ‘L’ limit screw then connect the cabl(link) to pull the rear derailleur right to check – and if necessary adjust – the ‘H’ limit screw.
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Low Normal

Some derailleur work in the opposite direction. The spring pushes towards the low gears and the cable pulls toward the high gears. If you have one of these the process is roughly the same. Start by positioning the ‘L’ limit screw then connect the cabl(link) to pull the rear derailleur right to check – and if necessary adjust – the ‘H’ limit screw.