“Fitting” the front derailleur
As the rear gear shifts, the direction from which the chain comes to the derailleur changes slightly. As a result, sometimes it becomes necessary to “adjust” the position of the derailleur when changing the reverse gear, even while remaining on the same front sprocket. “Fit” involves a slight movement of the frame by the shifter, but not enough to change gear, but only to eliminate friction against the sprocket.
On older shifters designed for friction shifters, “fit” was simply implied, but modern discrete shifters can almost always be set so that this fit is not necessary. For perfect shifting, you need to use a derailleur designed for the specific sprocket size, and the sprockets must be completely flat. The lower the derailleur frame is set to the sprocket, the less adjustment is required.
If the system requires a “fit”, you must do it. If the chain rubs against the switch frame, you will erase the frame so that you simply cannot expect any decent switching from it.
Often shifting problems are not caused by improper operation / setting of the derailleur, but by too much friction in the cable that controls it. High friction usually causes the frame to return slowly to the smaller sprocket under the force of the derailleur spring.
Typically, these problems occur in a short length of shirt leading from the pen to the switch. The front end of the shirt is exposed to dirt flying off the wheel and therefore rusts quickly, which seriously impairs shifting performance. This loop should be quite long so that there are no sharp bends. This loop is too short on most bikes.
Another problem area is where the cable runs under the carriage. In addition to slow shifting, friction can cause spontaneous shifting under load.
When you cut the shirt, the plastic flattens a little. It is useful after that to clean and round off the end, for example, with an awl. The shirt forms a strong loop just in front of the rear derailleur. I recommend that you first bend a piece of shirt to an approximate shape and only then cut it off completely.
If you cut a straight shirt, all the longitudinal wires are the same length, so when you bend it, the end of the shirt becomes oblique, since the wires going inside the bend and outside it travel a different path. I (of course, Sheldon) believe that cutting off already folded shirts makes the joint at the end of the shirt smoother. Also, there should be special tips at the end of the shirts; they maintain the correct shape of the end of the shirt, and also prevent the shirt from delamination.
With modern jackets, cable lubrication is no longer required. Indeed, it often only makes things worse because of the stickiness of the lubricant itself. However, a little light oil on the part of the shirt going to the switch won’t hurt. it will prevent rust.
Cables and shirts vary greatly in quality. I would recommend buying only the best cables and shirts. However, there are still situations where the switch spring cannot exceed the friction in this loop.
Front Derailleur Steering Angle Adjustment.
The front derailleur holder should be approximately parallel to the chain. Clarity depends on the accuracy of the angle of rotation.
- Shift the gears so that the chain is on the outer rear sprocket and the outer front drive sprocket.
- Examine the chain from above. The chain should be parallel to the outer plate of the derailleur holder (see photo).
- If the derailleur requires a turn, move the inner drive sprocket down to loosen the cable tension.
- Loosen the locking bolt and turn the speed selector to the correct position. Make sure this does not change the height. Tighten the locking bolt again (see photo).
- Move the outer sprocket back and check if the derailleur is level (see photo).
- Repeat this procedure until the speed selector plate is parallel to the circuit.
Note: The front derailleur clip usually leaves a mark on the frame to guide you when changing the steering angle.
Cable holder (front)
In the case of front derailleurs, some newer models are designed so that there are two ways to attach the cable. If the cable approaches the outside of the bolt (farther from the parallelogram pivot), the frame moves less for a given cable movement. This provides easier operation and easier fine adjustment. If the cable fits from the side of the parallelogram hinges to the bolt, the frame moves further for this cable movement. This is often required for discrete gear changes. Overshoot / Spontaneous Switching
Do the pedals sometimes slip when you put in a lot of effort? This is a common complaint, especially when the rider is pedaling. Indeed, this dangerous condition is a good reason to stay in the saddle and shift into low gears rather than standing up and riding high.
While a switch is often blamed for overshoot / jumping / spontaneous switching, it is very rarely caused by a switch malfunctioning.
Chain hopping can be associated with one of two unrelated problems: overshoot or spontaneous switching. The first step in solving a problem is to determine the type of problem: Overshoot involves the chain bouncing over the tops of the sprocket teeth under load. After this jump, the chain remains in the same gear. It is usually caused by wear on the chain and / or sprockets.
This is most likely to happen on the smallest star of the cassette, especially when used in conjunction with the smallest star in the system. This finding is discussed in more detail in the article on chain wear. Sometimes overshoot is also caused by bent links.
Spontaneous shifting feels exactly the same as overshooting, only after the jump, the chain is already in a different, higher gear (smaller sprocket). The reason for this is the combination of frame flexibility and cable friction.
If you’ve managed to tweak the rear derailleur, then tweaking the front derailleur will seem like child’s play. Everything is much easier and faster here.
Someone might ask: why did we mention the rear derailleur? Yes, because you can adjust the front derailleur only after successfully setting the rear (read how to do it).
Front derailleur height adjustment.
The first step to properly setting the front derailleur is to check your altitude. If the holder is too high above the drive sprocket, then it will not shift gears well. If it is too low, then it will not move the chain from star to star at all.
How To Adjust A Front Derailleur | Setup & Adjust Bike Gears
- Shift the derailleur so that the chain is on the middle drive sprocket. This will place the outer holder plate directly above the outer star.
- The distance between the teeth of the outer sprocket and the bottom edge of the outer holder plate must be 1.2 mm. A coin will serve as a tool for measuring the gap, since its thickness is approximately 1.5 mm. The coin should clearly fit into the slot (see photo).
- To change the derailleur height, first release the cable tension by shifting to the smallest drive sprocket. Then loosen the gear selector retaining bolt, adjust the height and retighten the bolt. Switch back to the middle guide sprocket and check the holder height (see photo).
- Repeat this procedure until the distance between the teeth on the outer drive sprocket and the bottom edge of the outer carrier plate is 1.2 mm.
Note: The front derailleur clip will usually leave a mark on. by which you can navigate when changing the height.
How to install?
Installing the front derailleur on a bicycle follows a few steps.
- The bike is mounted on. to make it easier to handle.
- Before installation, the mechanism must be thoroughly washed, and all rubbing parts must be properly lubricated.
- Attach the bike chain to the largest sprocket at the back and the smallest sprocket at the front.
- Loosen the cable adjusting screw.
- Slide the derailleur clamp onto the seat tube.
- Install a steel cable on the derailleur and tighten it.
- Check the position of the steel frame in sequential gear changes. If there is a skew or the distance between the frame and the stars is too large (small), then the mechanism must be removed and re-fastened to the seat tube.
- Tighten the fastening screw.
Just like the installation, the front derailleur on the bike is replaced.
Adjusting the screw “L” of the front derailleur.
Shift the chain to the inner rear sprocket and the inner driving chainring (see photo).
Check the tension of the cable. there should be no tension. To do this, turn the adjusting drum. If the cable still remains taut, loosen the cable tie bolt and retighten it (see photo).
Look at the gap between the holder’s inner plate and the chain. It should be one millimeter (see photo).
Why can’t I adjust the front derailleur
If you have not been able to clearly adjust the front derailleur of your bike several times, then most likely you have one of the following problems:.
- Wrong switch or star system.
- The switch is deformed or out of order.
- Tight running of the cable in the shirt.
- The shifter is out of order.
- The chain is too stretched.
- Derailleur, cable and chain are heavily soiled.
The configuration process can be described in several steps:
- We turn the adjusting screw L. It is necessary to set its position in such a way that the body of the mechanism places the chain at a minimum distance from its inner surface. It is important not to exaggerate and not bring the chain to the point of touching the frame. Thus, we have set up the upper border.
- Next, you need to secure the drive cable. To do this, you need to pull it up and tighten the fastening screw. In the case when the mount has an additional washer with a recess, fix the cable in this groove.
- After the work done, we transfer the chain to the star in the back of the smallest size and in the front to the largest. We start adjusting the lower limit of the switch. To do this, using the same L screw, we adjust the distance between the already outer boundary of the chain and the body of the mechanism. In both cases of border adjustment, a distance of 1-2 mm is recommended.
- It is important to check the work under load. The chain must run freely, without touching the frame. The throwing of the chain must be clear and fast. In this case, the setting can be considered correct.
Basic setup rules
The exact setting of the bike box depends on the set lift height and derailleur angle.
Switch / Big Star Mismatch
To keep the front derailleur as low as possible, the curvature of the bezel must match the curvature of the large star.
If your largest sprocket is larger than the derailleur is rated for, the rear of the frame will interfere with the sprocket teeth before the front of the frame is low enough to allow crisp shifting without the need for adjustment.
Front Derailleur Adjustment
If the largest sprocket is smaller than the derailleur rated, shifting will be fine, but adjustment will be necessary as the rear of the frame is higher than it should be, so the chain crosses far behind.
Low gear limiter “L” (“low”).
This limiter prevents the switch from dropping the circuit from the small star of the system. If it is too loose, the chain will fall off when trying to switch to the small star. If it is overly tightened, it will be difficult or almost impossible to switch to this star.
On older derailleurs, it is closer to the frame. On modern. the opposite. This is due exclusively to a slightly different switch arrangement.
First you need to place the chain on the smallest chainring in the front and the largest in the back. Then loosen the anchor bolt securing the cable, and also screw it in until it stops and unscrew the adjusting drum on the switch lever by one turn.
The chain should be as close as possible to the inner edge of the derailleur frame, but so that when pedaling, the chain does not touch it.
After that, you need to pull the cable and tighten the fastening bolt.
Front derailleur indexing adjustment.
- Switch to inner rear sprocket and middle front drive sprocket.
- The gap between the inner plate of the holder and the chain should be as small as possible, but there should be no friction. Spin the bike pedals to make sure that there is no friction in all places when spinning (see photo).
- To reduce the gap, increase the cable tension by rotating the adjusting drum (see photo).
- If the chain rubs against the inner plate of the holder, reduce the tension on the cable by rotating the adjusting drum (see photo).
- If the adjusting drum is unscrewed to the limit, then return the cable tension to its original position. Unscrew the adjusting drum all the way in the opposite direction. Switch to the inner chainring. Loosen the cable tightening bolt, pull gently and retighten the bolt. Repeat the cable tension adjustment as described above (see photo).