Shimano Front Derailleur Adjustment: A Guide to Cable Tension, Limit Screws, and More

Published on 05/30/2023 · 5 min readTo most of us, bike maintenance can be intimidating! In this guide, Cycling Expert Mikael Hanson gives a step-by-step on how to adjust a Shimano front derailleur!
Mikael Hanson, Cycling Expert
By Cycling Expert Mikael Hanson

Photo by Tim Foster

There is nothing quite like the allure of cruising along an open country road on your bicycle—taking in the sun and scenery while getting a bit of exercise at the same time. However, a bike that is not functioning properly can quickly turn a terrific day on the road for the worst. Missed shifts or dropping a chain while shifting is something that can make for a long day in the saddle—especially if you are a long way from home. Simple tasks like fixing a flat, repairing a broken chain, and adjusting front derailleurs can not only get you back on the road faster, but also save you money.

A front derailleur is the mechanism on the bike attached to the seat tube just above the crankset that is responsible for moving the chain between the various chain rings. This piece will focus on Shimano front derailleurs, and, specifically, how one goes about adjusting them for optimal performance. Shimano is the largest bicycle component manufacturer in the world, so it is likely your bike has Shimano derailleurs.

Most modern derailleurs are mechanical in nature, meaning they use a cable and a lever to shift the gears. The models of mechanical front derailleurs from Shimano include Dura-Ace and Ultegra (which are also available in electronic), 105, Tourney, Claris, Sora, and Tiagra to name a few. Keep in mind, mechanical front derailleurs from other manufacturers like SRAM and Campagnolo will largely operate in the same manner; so the adjustment steps outlined here should also apply.

Basic Front Derailleur Parts

Shimano Ultegra front derailleur attached to frame via Braze on mount. Photo by Mikael Hanson

A front derailleur consists of…

  • A main body with an arm and pivots (for moving the cage)
  • A cage that straddles the chain and chainrings
  • A cable anchor point and two limit screws (a high and low)

Here are the steps one needs to follow for front derailleur adjustment:

Step 1: Cleaning

Like any mechanical part, when a front derailleur is clean, it will always perform better than when covered in years’ worth or grease and road grime! Personally, I wipe down the chain on my bicycle after every ride with a cloth and some simple degreaser cleaning fluid. I pour a small amount on a cloth, wrap it over the chain, then slowly pedal backward to let the chain run through the cloth. After several rotations, I then put a few drops of my favorite bike lube on the chain and again pedal the bike backward to allow the lube to work into the links. I then wipe it down with a clean cloth. It takes five minutes at most!

Another part that goes along with keeping a bike clean and well-maintained is its cables. If the bike has been stored outside or is many years old, chances are the cables could have some buildup or even corrosion on them inside the housing, which will greatly impact the shifting action. I replace the derailleur (and brake) cables on my bikes every other season and let my local bike shop handle that job!

Step 2: Height and Angle

Proper front derailleur height is important to ensure proper shifting action. You want to make sure there is 1–3mm of clearance between the cage and the teeth of the largest chainring. A penny is a good guide in measuring this distance, as it is typically 1.5mm wide.

The front derailleur is attached to the bike frame either by a clamp or bolted to a braze-on. Either way, one would need to loosen the bolt holding the derailleur in place when the bike is in the lowest gear (so there is enough cable slack) and move up or down to arrive at proper spacing.

Additionally, you should also check the alignment of the front derailleur cage. Make sure the outer edge of the derailleur cage runs parallel to the chain.

Step 3: Cable Tension

With your bike shifted into the smallest (or easiest) gear up front, pull the front derailleur cable tight and secure by tightening down the anchor bolt. Most bikes will also have a barrel adjuster on the cable to the front shifter; this will allow you to fine-tune the cable adjustment here.

Step 4: Limit Screws

High / low limit screws - most common place for limit screws is on the top of derailleur. Photo by Mikael Hanson

The next step is to check the limit screws (see picture above) to ensure the derailleur is not shifting the chain off the inner or outer chainring.

There are two limit screws; the first, the upper limit screw, might be marked “H” and is located close to the large outer chainring. The other, the lower limit screw, might be marked “L” and is inside closer to the frame and inner chainring.

The lower limit screw prevents the cage from moving too far in and allows the chain to drop inside of the small chainring, while the outer/high limit screw is used to make sure the cage does not shift the chain out over the large chain ring. A small Phillips screwdriver will move these limit screws.

Step 5: Testing

At home bike stand - a simple rear wheel bike stand allows for ease adjustment. Photo by Mikael Hanson

Once you have gone through the steps outlined above, it is time to test your adjustments. This is best done by having your bike in a bike stand like found at a bike shop. Or, one can get a simple stand that attaches to your bike’s rear triangle and lifts the rear wheels off the ground to allow you to pedal your bike and shift gears (see picture above).

However, testing the shifting while your bike is on a stand might not offer enough tension to truly see if your adjustments are sound. Taking the bike for a quick spin will be the ultimate test of your adjustments.

Final Thoughts

Once you’ve mastered adjusting the front derailleur, then you can turn your attention to the rear derailleur. This largely works in the same fashion and has similar limit screws and anchor bolts for cable! To explore more Cycling articles as you pursue your journey in the sport, check out the Expert Journal here on Curated.

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