BikeCo Tips & Tricks: Shifter Barrel Adjustment
In this How-To we have a video and write-up showing some basics of shifting trouble shooting as well as how to use your barrel adjusters.
Barrel adjusters are used for minute shifting corrections and are useful on new builds due to cable stretch (or housing shrink depending on how you look at it!).
MTB Shifter & Derailleur Concepts
Your bike changes gears as the shifter adds or releases tension on the cable. This pulls the derailleur up towards the larger cogs or drops it down to the smaller ones.
If you’re having shifting issues across the entire cassette its’ most likely a cable tension problem.
If the chain is slow to climb the gears and doesn’t want to settle into the largest cogs it’s likely you need to add tension to the cable.
Conversely if the chain is slow to descend gears or doesn’t reach the smallest cog you probably need less tension.
If the shifting problem is isolated to only a few gears it’s more likely that you have an issue with something bent, loose, or aged housing.
For this write-up we’re going to focus on the small tension changes the shifter’s barrel adjustment is capable of.
Using your Barrel Adjuster
The barrel adjuster makes small tension changes to your shift cable by increasing or decreasing the length of the housing, ferrules and mounts between the shifter and the rear derailleur.
The barrel adjuster is a hollow bolt which the shift cable is routed through.
When you need to add tension to the shift cable you need to increase the length of the housing between shifter and derailleur mounts. You achieve this by loosening the barrel adjuster.
Most barrel adjustments only require a coupe clicks. Don’t go crazy spinning the adjuster or you might end up further in the weeds than you started!
In the image below you see three oversimplified sketches.
The top sketch illustrates the barrel adjuster the furthest out, or loose. You see how this increases the length of the housing assembly.
On the other hand, the bottom image shows the shortened housing assembly by tightening in the barrel adjustment. This would relieve some cable tension allowing the chain to get into the smaller cogs and improve shifting down the cassette.
Other Possible Shifting Issues
If a barrel adjustment doesn’t solve your issues there are some other places to review.
Is the derailleur tight? Is the derailleur hanger tight? Are both of these straight?
Is the rear axle properly torqued?
Does the hub need adjustment?
Cable & Housing
What is the condition of the cable and housing? Worn housing creates an interesting and sometimes hard to identify set of problems.
Check if your housing has exposed “lady fingers” at the cable ends. These steel strands that extend as the housing retracts aren’t typically straight. At an angle with a rotating force they will change cable tension creating inconsistent shifting.
Does your cable slide easily in the housing? Old fouled housing creates inconsistent shifting.
Recently I was shooting a “how-not-to” concept and came across an issue I hadn’t seen. I was showing how to trim cable lady fingers back and tried to reuse the inner cable. It wasn’t a good plan and I articulated it in the video – but I didn’t know what a pain it was about to become.
The trimmed end of the old cable frayed as I reinstalled it. I trimmed some off to get it to clear the derailleur. Well, once I took the tension off those strands all hell broke loose. Suddenly something I’ve done countless times was near impossible.
I had to stop and think: what am I missing? I didn’t have all of the gears. It would hold a gear and suddenly not. Thinking back to “it’s either movement or tension” I finally decided to look at the shifter.
You can see the rats nest of cable strand that pulled itself all the way into the shifter.
Well, there was one in the housing too. No way this was going to work well!
Point is: cable and housing is critical to your shifting performance.