Tuning Your Bicycle Gears

Before we jump into how to tune your bicycle gears, for those of you who are new to geared bicycles, it is important to understand bicycle gearing mechanisms function. Once you do, you will be able to better understand each aspect of the tuning process - I know I did! Geared bicycles have small levers on the handlebars - shifters, that control the shifting between individual gears. These shifters, when engaged, release specific amounts of the gear cable(s) to activate the front and rear gear mechanisms i.e. derailleurs. When the shifter has moved enough gear cable to make the derailleur shift the chain from one sprocket to another, it makes a small ‘click’ sound, to let you know you’ve achieved a single gear shift. Next, the ‘limit’ screws are in place to set the front and rear derailleurs’ shifting limits so as to not over shift the chain off of the final smallest and largest sprockets on the rear cassette and the inner and outer chainrings. The last aspect is cable tension - and to figure out how much of it is required to allow one click of the shifter to deliver a single gear change. Now, let’s dive into how to actually do this…

Firstly, check and ensure that the derailleur hanger is straight. The rear derailleur is fitted onto the derailleur hanger, which is a small piece of metal that hangs off the rear chainstay. To ensure that it is straight, view the hanger from behind and make sure that it is vertical when the bicycle is upright. A straight hanger ensures that the ‘jockey’ wheels line up directly underneath each sprocket as the gears are changed. Typically, the derailleur hanger can bend if your cycle falls on the derailleur or the derailleur is impacted by another object/ rough handling and improper storage. You can straighten out the hanger, if it is slightly bent, you might have to replace it if it is bent beyond repair. If you are a beginner, you might need to take your bicycle into a store to have this done, well. For the front derailleur, the derailleur cage must be in line with the chainrings, and the lower edge of the cage must not touch the tops of the chainring teeth. Ideally, about 1-3mm clearance is advised for optimal shifting.

To do this, you must first undo the cable anchor pinch bolts on the derailleurs. Next, move the inner cable in and out of the outer housing to check for damage. If you find that the cable feels rough or tough and not smooth, you will need to clean it and lubricate it well. If the cable looks rusted, you will need to replace it with a new one. Ensure the cable follows the correct route through the derailleurs, there are often specific channels, grooves and holes the wire must pass through in order for it to function accurately. Route the end of the cable through the cable anchor pinch bolt. Remember to completely tighten the bolts.

1. Adjust The Limit Screws

With no cable tension, the rear derailleur will be at rest - this is required to adjust the limit screws. To do this, ensure that the derailleurs upper jockey wheel is positioned directly under the smallest cassette sprocket. If it isn’t, turn the screw marked ‘H’ to adjust its position. Turn it clockwise or anti-clockwise until it is directly in line with the smallest sprocket. Similarly, adjust the largest sprocket by moving the derailleur to its furthest position and ensuring that it is under the largest rear sprocket. Make adjustments to the screw marked ‘L’ until the top jockey wheel is directly in-line with the largest sprocket. Let the derailleur return to its rest position under the smallest sprocket. Finally, turn the rear derailleur’s barrel adjuster fully in, then out for two full turns. This provides you some leeway for further adjustments.

2. Adjusting Cable Tension

To do this, it is most important to ensure that the rear shifter is fully downshifted i.e. at 1. Use a cable tension puller tool (or if you don’t have one - just pull on the cable with whatever you have), and place tension on the inner cable. As you reach full tension, the pull-force on the cable will start to try to move the derailleur inwards i.e. towards the second sprocket. At the point where the jockey wheel begins to twitch to do so (remember to not let it move more than .5mm), put the cable anchor pinch bolt up tight. The derailleur will relax the .5mm, leaving it directly under the smallest sprocket with the optimum starting tension on the inner cable.

3. Final Adjustments

To do this, you will have to have your bicycle off the ground - preferably on a stand. First, rotate the cranks forward and click to shift one gear on the rear gear shifter. You should have a clean movement of the rear derailleur inwards, shifting the chain onto the adjacent sprocket. If so, keep shifting one sprocket at a time all the way up and all the way back down. If the shifting has a lag, or is not precise, you will need to use the barrel adjuster to add or remove tension as required. To make this adjustment, you will need to shift the chain onto the middle of the cassette 4th or 5th sprocket and make the necessary adjustments with the barrel adjuster to ensure the jockey wheel lines up with the sprocket. Never adjust more than a quarter turn in any direction without checking the effect on shifting first.

1. Adjusting The Front Derailleur

To adjust the front derailleur, it must be positioned such that the outer cage plate is in line with the outer chainring. Any noise or poor shifting indicated that it is not in-line. Next, check and adjust the position of the lower edge of the derailleur cage so that it is 1-3 mm clear above the large chainrings teeth, and then tighten the fixing bolt. Next, turn the front derailleur barrel adjuster all the way into the shifter, then out for two full turns. To set the limit screws, shift the front derailleur into the smallest chainring and the rear derailleur into the largest rear sprocket. Turn the inner limit screw until the inner face of the derailleur cage is as close as possible to the chain without touching it. Adjust the cable tension by loosening the cable anchor pinch bolt, use a cable puller tool (or anything similar on hand) to pull the slack from the cable before retightening the cable anchor pinch bolt. To set your front derailleur outer limit screw, shift the front derailleur into largest chainring and the rear derailleur into the smallest sprocket. Turn the outer limit screw until the inside edge of the derailleurs outer cage plate is as close as possible to the chain without touching it.

2. Final Adjustments

Run through your front gears to assess the shifting performance, by placing your bicycle above the ground on a stand and moving the pedals forward. Use the shifters to shift between the front gears. The shifting should be smooth and crisp. If the derailleur is sluggish to reach the outer chainring, add some tension to the cable. Similarly, if the derailleurs inner cage plate is too close to the chain (over shifting), then reduce tension. Always make adjustments a quarter turn at a time and check performance between adjustments.