Indexing Gears

Having your gears properly indexed, that is, one “click” in the lever moving the chain precisely to the next cog, makes your cycling experience safer and more enjoyable.

indexing gears

Gears that aren’t indexing properly can also be a sign that there is something wrong with your transmission.

If you want to learn about indexing gears and find out why they are not clicking in sync, then you have come to the right place.

When you know that all the components that contribute to accurate gear shifting are in good working order, the next stage is to set up the indexing correctly. This task is much easier to perform if you use a work stand. It makes the multitasking involved in indexing gears so much easier.

indexing gears

Parts of the derailleur

Limit screws- These 2 little screws don’t control the indexing. Their job is to stop the derailleur when it reaches the lowest or highest gear.

They prevent the derailleur from throwing the chain into the wheel or the frame. The limit screws on the front and rear derailleurs are normally set up by the cycle retailer. Once they have been set up they shouldn’t be touched again. 

“B” tension screw or body tension screw- This is only found on the rear derailleur. Its function is to set up the distance between the cogs and the top jockey wheel. Done correctly it will make the gear changing more responsive. 

Barrel adjuster– This is found on most rear derailleurs. It is a bolt with a knurled piece of plastic around it and is used to adjust indexing by loosening or tightening your gear cable.

If your derailleur doesn’t have one or you want to tune your front gears, then the barrel adjuster is placed on or near the shifter.

Indexing gears– adjusting the rear gears.

1. Move the shifter to the highest gear.

Some levers have numbers on them. The highest number indicates the highest lever.

indexing gears

If you’re not sure how to do this then for drop bars watch the video here

2. Loosen the cable on the derailleur.

3. Reset the barrel adjuster.

Turn it clockwise until it stops and then turn it anticlockwise two revolutions.

4. Remove the slack from the gear cable.

Hold the cable and move the shifter to the lowest gear.

While still holding the cable, pull it and shift to the highest gear.  

Don’t release the cable until you have tightened it. 

5. Set up the B-tension screw.

Shift the gears to the lowest cog at the back.

Check the gap between the cog and the top jockey wheel. The top pulley should be as close to the sprocket as possible without rubbing, about 6mm.

If the jockey wheel is too far from the sprocket then turn the B-tension screw anticlockwise until it is in the right position.

If the top pulley rubs on the cog then turn it clockwise until it is in the right position.

6. Adjust the rear gears.

When to loosen the cable

Now shift the gear up one click and see if the chain derails to the next gear. If the top pulley doesn’t move enough to align with the desired cog then the gear cable needs to be loosened.

Using the gear shifter, move the chain to the highest gear, shift two clicks down.

The gears might make a noise or even shift to the cog that doesn’t match the gear shifter position. While spinning the cranks turn the barrel adjuster clockwise half a turn at the time and monitor the chain position.

Repeat the process until the chain moves smoothly and quietly in the correct gear.

When to tighten the cable

If the top pulley moves too far to align with the desired cog, then the gear cable needs to be tightened.

Move to the highest gear and then shift two clicks down. The gears might make a noise and/or not reach the desired cog. While spinning the cranks turn the barrel adjuster anticlockwise half a turn at a time and monitor the chain position.

Repeat the process until the chain moves smoothly and quietly in the correct gear.

7. Test the gears.

Move the right hand gear lever so that the chain moves up and down the sprockets making sure that the gears are indexing correctly. This is a good time to do fine tuning to make sure that the gears are moving evenly in both directions. 

Indexing gears– adjusting the front gears

Indexing front gears means not only accurate shifting but also being able to use all the rear gears on each chainring without chain rub. However, if the front derailleur is not fitted correctly or not compatible with the frame, chainset or shifter you will be less likely to achieve perfect indexing. 

1. Move the shifter to the lowest gear.

2. Loosen the cable on the derailleur.

3. Reset the barrel adjuster.

Turn it clockwise until it stops and then turn it anticlockwise two revolutions.

4. Remove the slack from the gear cable.

Hold the cable and move the shifter to the highest gear. While still holding the cable, pull it and shift to the lowest gear. Tighten the pinch bolt but don’t release the cable until you have secured it.

5. Adjust the front gears.

Move the gear lever and see if the chain derails to the next gear. If the derailleur struggles to move the chain to the next gear then the cable needs to be tightened.

While spinning the cranks turn the barrel adjuster anticlockwise half a turn at a time until the chain moves to the next cog.

Now shift the rear gear to the largest cog.

If the chain rubs on the back plate of the front derailleur, you will need to loosen the cable.

Turn the barrel adjuster clockwise until the chain just clears the back plate.  

Shift the rear derailleur to the highest gear. If the chain rubs on the front plate of the front derailleur

then you will need to tighten the cable by turning the barrel adjuster anticlockwise.

If the derailleur moves the chain to the next cog, shift the rear derailleur to the lowest gear.

If the chain rubs on the back plate of the front derailleur then the cable will need to be loosened.

Turn the barrel adjuster clockwise until it just clears the back plate.  

Move the rear derailleur to the highest gear.

If the chain rubs on the outer plate then you will need to tighten the cable by turning the barrel adjuster anticlockwise just enough to stop rubbing. 

6. Test the gears.

Go up and down the front gears to make sure that they are indexing correctly and that there is no chain rub on the front derailleur while using any of the rear gears. 

If you cannot find the balance then your problem is not with the indexing and you will need to seek further help from a friend or bicycle repair shop.

Setting the limit screws 

If you know that your limit screws aren’t adjusted properly, then you will need to do this. 

Rear limit screw.

  1. Loosen the cable.
  2. Locate the high and the low screws.  The High gear screw should have an “H” next to it and the low an “L”.
  3. Pedal the crank forward and manually push the derailleur to the largest cog. If this action causes the chain to come off the cog you will need to turn the “L” screw clockwise. To do this, hold the derailleur so that the top jockey wheel is under the largest cog.  Screw the limit screw until you feel some resistance.  It should now be set. If the same action causes the derailleur not to reach the biggest cog then turn the “L” screw anticlockwise until it moves the chain to the biggest cog.
  4. To adjust the high gears, stand behind the bike and make sure that the smallest cog and the jockey wheels are in line. If it’s out of alignment then turn the screw anti clockwise to bring it away from the lower gears and clockwise to move it away from the frame and onto the smallest cog.
  5. Tighten the cable.

Front limit screw

  1. To adjust the front limit screw, start with a loose derailleur cable. Move the rear derailleur to the lowest gear and spin the cranks. If the chain is rubbing on the back-plate of the front derailleur, then turn the low limit screw, labelled “L” anti-clockwise until it just stops rubbing. 
  2. Shift the rear gears so that the chain moves to the highest gear. See if the chain is rubbing on the front plate of the derailleur.  If it is, then you will need to turn the “L” screw clockwise.
  3. Check to see if you have adjusted it correctly by going back to the lowest gear and make sure that it doesn’t rub on the back plate.  If you can’t adjust the low limit screw to not rub then either you have an incompatible front derailleur or chainset, the derailleur is set at the wrong height and/or angle or the chainset is bent.
  4. Tighten the cable.
  5. To set the high or “H” screw, put the front derailleur on the largest cog at the front and the smallest at the back. Manually pull the cable. If the chain rubs on the outer plate, then turn the high screw anti clockwise and recheck our cable tension. If it rubs on the inner plate, turn the “H” screw clockwise.

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