Small things can ruin potentially great rides. Let’s take a minute to go over one very simple adjustment that can make a world of difference on your bike. Many of you might already know how to properly use the barrel adjuster on your rear derailleur, but I know there are also a lot of cyclists out there who could use a few hints.
Barrel adjusters are simply a type of bolt that essentially lengthens or shortens the cable housing, depending which way you turn them. They are found on all mechanical cable gears and brakes, today we’ll cover the rear derailleur. On road bikes you will find the barrel adjuster on the rear derailleur itself, and sometimes an additional one on the frame, while on mountain bike set ups it is normally found on the shifter, and sometimes on both.
A mis-aligned derailleur can cause the chain to “jump” around between gears, cause loud rubbing noise, missed-shifts, etc. In short, it can put a real damper on your ride. The barrel adjuster allows you to re-align your derailleur with the cogs.
Turning the adjuster clockwise shortens your cable housing, therefor slackening the cable, as the same length of cable now has less distance to travel. This moves the derailleur to the outside of the bike, towards your smallest cogs (harder gears). Turning it counter-clockwise will tighten the cable, moving the derailleur towards the spokes and your bigger cogs (easier gears). This may seem counter-intuitive at first, but once you do it several times it becomes easier.
*There are some “high-low” derailleurs out there, though they are not common today. If you have one, the barrel adjuster will move in the opposite direction described above when turning the barrel adjuster.
You want the chain to be centred between the cogs, when looking at then from behind (like in the picture). When it is properly aligned, the chain should shift smoothly from one cog to the next, without getting stuck between gears and jumping from one to another.
There are many variables such as derailleur quality, condition, chain lubrication, chainline, etc. that affect shifting, but knowing how to align your rear derailleur properly is a great first step to keeping your bike shifting well and identifying the source of rubbing chains and poorly shifting gears.
Understanding simple bicycle maintenance can have a profound impact on your rides, never be afraid to take your bike to your local shop for help, but learning how to do simple adjustments on your own.