How to adjust limit screws

In this blog we are going to teach you how to adjust limit screws. Every front and rear derailleur will have two screws that control how far it moves at its limits.

Without them the derailleur wouldn’t be able to stop when reaching the highest and lowest gear pushing the chain of the cogs.

On rear mechs the limit screws are usually placed either at the back or at the front of the derailleur body.

Front derailleurs have the limit screws at the top.

How to adjust limit screws when you can’t see which is H and which is L:

The other, usually marked as L (for low gear) stops the chain from falling off the smallest chainring at the front and biggest cog at the rear.

The end of the screw embedded in the derailleur body has either a crosshead screwdriver fitting

or an allen key fitting.

Rear

Undo the gear cable and stand behind the mech. Choose any of the limit screws and start turning it anti-clockwise. If it is the high gear limit screw then the derailleur arm will move right towards the frame. If it doesn’t move then this is a low limit screw.

Front

For the front derailleur first move the chain onto the lowest gear. Undo the front gear cable. While looking from the top choose any of the limit screws and turn it anticlockwise. If it is the low limit screw then the derailleur will move left towards the frame. If it doesn’t move then this is a high limit screw.

Will limit screw adjustment help with my gears slipping/clicking/not moving properly?

Often limit screws are wrongly seen as a solution to gear changing problems. Be aware that turning them will not improve indexing and may cause the chain to come off creating more serious problems.

When do I need to know how to adjust limit screws?

When setting up a new bike. Sometimes the new bike may require further set up of the limit screws.

When replacing the derailleur. The limit screws on a new derailleur are set up below the reach limits so they don’t cause the chain to come off before the mech is adjusted. 

How do I know if mine are adjusted properly?

If the low limiter on either the front or the rear derailleur is screwed in too far then the chain will not shift to the lowest gear.

If the low limiter on either the front or the rear derailleur is not screwed in enough then the chain will come off the lowest gear.

If the high limiter on either the front or the rear derailleur is screwed in too far then the chain will not shift to the highest gear.

If the high limiter on either the front or the rear derailleur is not screwed in enough then the chain will come off the highest gear.

Be aware that if your limit screws were set up correctly and any of these symptoms occurred later in time, it is less likely that limiters need to be adjusted and it is an indication of other gear problems. 

So before you jump to adjusting the limit screws, first check and sort out the following:

Rear checks:

Is the hanger bent?

Is the cable loose or tight?

Is the derailleur bent, damaged or seized?

Front checks:

Is the derailleur aligned with the chain?

Is the derailleur mounted too high?

Is the cable too loose or too tight?

Is the derailleur damaged or seized?

If the crankset was replaced recently, does it sit either further or closer to the frame than the previous one?

Setting up the rear derailleur limit screws:

• Put the bike on a stand.

• Move the rear derailleur to the highest gear.

• Loosen the gear cable.

• Locate the high limit screw.  
• If there is no marking to indicate which one is which then to work this out choose any of the limit screws and start turning it anti-clockwise. If it is the high gear limit screw then the derailleur arm will move right, towards the frame. If it doesn’t move then this is a low limit screw.
• To adjust the high limit screw, make sure that the smallest cog and the jockey wheels are in line. 

• If the top jockey wheel is offset to the right then turn the high limit screw clockwise quarter of a turn at a time until it lines up with the smallest sprocket.

• If the top jockey wheel is offset to the left then turn the high limit screw anticlockwise quarter of a turn at a time until it lines up with the smallest sprocket.

• To adjust the low limit screw pedal the crank forward and manually push the derailleur to the largest cog. 

• If the top jockey wheel is offset to the left then turn the low limit screw clockwise quarter of a turn at a time until it lines up with the largest sprocket.

• If the top jockey wheel is offset to the right then turn the low limit screw anticlockwise quarter of a turn at a time until it lines up with the largest sprocket.

•  Once you’re happy with both limit screws, move the chain back to the highest gear, tighten the cable and check the gears.

Setting up the front derailleur limit screws:

• To adjust the front limit screws, first move the front and rear derailleur to the lowest gear. 

• Loosen the gear cable. 

• Locate the low limit screw.
• If there is no marking to indicate which one is which then to work this out, while looking from the top, choose any of the limit screws and turn it anticlockwise. If it is the low limit screw then the derailleur will move left towards the frame. If it doesn’t move then this is a high limit screw.
• If the gap between the chain and the backplate of the front derailleur is more than 2-3 mm, then turn the low limit screw clockwise quarter of a turn at a time until you achieve a 2-3 mm gap. 

• If the chain is rubbing on the back-plate of the front derailleur, then turn the low limit screw, anti-clockwise quarter of a turn at a time until you have a 2-3 mm gap.

• Now shift the rear gears so that the chain moves to the highest gear.

• Tighten the front gear cable. 

• Change the front gears to the largest chainring.
• If the chain comes off or the gap between the chain and the front plate of the derailleur is more than 2-3 mm, then turn the high limit screw clockwise quarter of a turn at a time until you achieve a 2-3 mm gap. 

• If the chain is rubbing on the front plate of the derailleur, then turn the high limit screw anti-clockwise quarter of a turn at a time until you have a 2-3 mm gap.

• If the gap is changing while spinning the crank then the chainring is bent and replacing the crank will be the next step.

Now you should know how to adjust limit screws, but if you still feel unsure, check out our handy video or bring your bike down to our repair shop and we can take a look at it for you. After setting up correctly and barring any accidents, you can be sure that you can cycle without your chain coming off.