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===Einstellmöglichkeiten des Umwerfers===
===Einstellmöglichkeiten des Umwerfers===


#Chain slope and derailer selection<br>On a bicycle with a small rear wheel, high bottom bracket or steep seat tube, the chain slopes down more toward the rear wheel, and the chain cage of the front derailer needs to sit farther to the rear. Instructions for many clamp-on front derailers specify a range of angles. The front derailer of some bicycles attaches to a special slotted tab, which may be brazed, bolted or glued onto the frame. The tab limits the range of chainwheel sizes that can be used, but it can be aligned ideally for the particular bicycle. Another solution is a Shimano E-type front derailer, which attaches to the bottom bracket, so it can be rotated to any needed angle --though it can be used only with the particular chainwheel sizes for which it is designed.
====Kettenverlauf und Wahl des Umwerfers====
#Clamp Position<br>The most critical adjustment of a front derailer is its attachment to the bicycle frame. This must be set correctly before you attempt to adjust the limit stops. All derailers except the E-type derailer allow two adjustments, for angle (as seen from above) and height.
Bei eine Fahrrad mit einem kleinen [[Laufrad|Hinterrad]], hohem [[Tretlager]] oder einem steilen [[Sitzrohr]]winkel, verläuft die Kette abwärts gerichtet richtung Hinterrad. Daher muss der Umwerfer weiter nach hinten ausgerichtet werden. Die Anleitungen für klemmbare Umwerfer spezifizieren hierfür einen bestimmte Bandbreite an möglichen Winkeln. Bei manchen Fahrrädern werden die Umwerfer an einem speziellen [[Anlötsockel]] befestigt. Dies limiteirt deutlich die Auswahl an Umwerfern, die montiert werden können. Er kann jedoch für das jeweilige Fahrrad sehr exakt eingestellt werden. Eine weitere Lösung wäre eine [[Shimano]] [[E-Typ Umwerfer]], der am [[Innenlager]] befestigt wird und im notwendigen Winkel ausgerichtet werden kann. Dise können jedoch nur mit Kettenblattgrößen verwenmdet werden, für die sie spezifiziert wurden.
#*Angle<br>        of the front derailer is judged by looking down on the cage from above. Modern front derailers have very subtly shaped cages, so it is not always easy to tell when the ideal adjustment has been made. In general, the centerline of the cage should be parallel to the centerline of the frame. Rotating the derailer so that the back of the cage is farther out will sometimes improve shifting to the small ring of a triple by preventing overshifting, but may cause increased need for trimming on the larger rings. It may also cause the crank to strike the cage.<br>        Rotating the derailer so that the back of the cage is farther in will help reduce the need for trimming on the large chainwheel, and will provide crisper downshifting, but with a greater tendency to overshift on the inside. This may be appropriate on bicycles equipped with an anti-derailment device.
#*Height<br>        of the front derailer is a principal factor in how well it will shift. Manufacturers commonly recommend 2 mm clearance between the bottom of the outer cage plate and the teeth of the large chainwheel. This is a bit of an oversimplification. Best performance will result from the very lowest position that still just barely keeps the cage from hitting the chainwheel teeth. The lower you can get it, the better it will shift, and the less you will need to trim the front derailer.
#Derailer/Chainwheel Mismatch<br>    To get the front derailer as low as possible, the curvature of the outer cage plate has to match the curvature of the largest chainwheel.<br>    If you use a larger chainring than the derailer was designed for, the rear of the cage will hit the teeth of the big chainring before the front of the cage gets low enough to provide crisp shifting without the need for trimming.<br>    If you use a smaller chainring than the derailer was designed for, it will shift OK, but you'll have to do a fair amount of trimming, due to the rear of the cage being higher than it should be, so that the chain crosses through it farther back.<br>    Lately I've started modifying front derailers for improved shifting with larger rings. I have a Shimano RSX front derailer on a bike with 50/38/28 Biopace (the sweep of a 50 Biopace is comparable to that of a 52 round.) The RSX front derailer works great on its intended 46/36/26 setup, but the cage doesn't match the curve of the larger chainring. In a couple of minutes with a grinding wheel, I removed a good bit of metal from the bottom rear of the outer cage plate, and a bit from the bridge section where the inner and outer cage plates connect at the back. This made the derailer match the curvature of the larger chainwheel, and allowed me to set it low enough to provide good chain control. This setup now works fine with an STI indexed shifter that doesn't permit "trimming" the front derailer.
#Low-gear limit stop.<br>    The low-gear limit stop stops the derailer from shifting past the smallest chainwheel and throwing the chain onto the bottom bracket shell. If the stop is too loose, the chain will fall off when you try to downshift to the small chainwheel. If too tight, you will find it difficult or impossible to shift down to the small chainwheel.<br>    On older front derailers, the low-gear stop is the one closer to the frame. Many newer designs reverse this position for reasons relating to the mechanism used.<br>    The basic adjustment for the low-gear stop is to set it so that the chain just barely clears the inner plate of the cage when the lowest gear (small front, large rear) is selected. This will usually be the best position for double-chainwheel setups, and will permit the use of most or all of the rear sprockets with a minimum of trimming.<br>    For triple chainwheels, it will sometimes be necessary to adjust the low-gear stop a bit looser, so that the outer plate of the derailer can travel far enough to knock the chain off of the middle ring.
#*Anti-derailment devices<br>    In some instances, you may find that one adjustment of the low-gear stop causes the chain to derail past the small chainring, but a tighter setting results in slow downshifting to the small ring.<br>    In such cases, a good, if inelegant, solution is sometimes to install an anti-derailment device that clamps to the seat tube. These products, such as the 3rd Eye Chain Watcher ® and the N-Gear Jump Stop ® set up a barrier preventing the chain from overshooting the small ring, no matter how loose the low-gear stop is set. This allows the low-gear stop to be set to allow the derailer to move farther inboard for faster, more precise shifting, even under some load. These devices can often save the day when extra-wide range gearing is used on a mountain bike or tandem.
#High-gear limit stop<br>    The high-gear limit stop is pretty straightforward. It should be set so that the chain almost rubs on the outside plate of the front derailer cage when the bicycle is in its highest gear (large front/small rear). This will reduce the need for trimming as you shift the rear derailer.<br>    If the shift to the large chainwheel is slow, make sure that you aren't pedaling too hard: front upshifting requires being ready to have the cranks slow down when the shift takes place. If the shift is unreliable even when you are pedaling lightly, you may be able to improve it by loosening the high-gear stop a bit. If you do so, check to make sure that the derailer cage is not moving so far out that it can be struck by the crank as it goes by.<br>    Sometimes front upshifting may be improved by rebending the front edge of the inner cage plate outward a bit. This may be done with an adjustable wrench. This is rarely necessary on modern front derailers, but used to be a very common trick on older, cruder designs.


====Klemmposition====
Die kritischste Variable des Umwerfes ist die Montage des Umwerfers am Rahmen. Der Befestigungspunkt muss korrekt gewählt werden bevor man die Begrenzungsschrauben einstellt. Bis auf den E-Typ Umwerfer erlauben alle Umwerfer eine Justage in Höhe und Winkel (von oben gesehen).
;Winkel
Der Winkel des Umwerfers wird mit Blickrichtung von oben auf den [[Käfig]] bestimmt. Moderne Umwerfer haben subtil geformte Käfige. Daher ist es nicht immer leicht, die ideale Ausrichtung zu sehen. Im allgemeinen solte die Mittellinie des Umwerfes parallel zur Mitellinie des Rahmens ausgerichtet werden. Wenn man den Umwerfer so dreht, dass seine hintere Seite nach außen verdreht ist, kann das den Schaltvorgang auf das kleine Kettenblatt einer [[Dreifachkurbel]] verbessern und überschalten verhindern. Jedoch muss man sich mehr Mühen beim Trimmen der Einstellung auf dem großen Kettenblatt geben. Unter Umständen kann auch die Kurbel an den Käfig stoßen.<br>Wenn man den Käfig so ausrichtet, dass sein hinteres Ende eher nach inen gerichtet ist, reduziert das die Mühe beim Trimmen auf dem großen Kettenblatt, fördert knackigeres Schalten auf die kleiner Kettenblätter und erhöht die Tentenz über das kleinste Kettenblatt zu überschlaten. Deher solte man das nur bei Fahrrädern mit [[Kettenstopper]] machen.
;Höhe
Die Höhe des Umwerfers ist der prinzipielle Faktor für gutes Schaltverhalten. Hersteller empfehlen zumeist rund 2mm Abstand zwischen den Zähnen des Kettenblatts und der unteren Kante der Käfigaußenseite. Das ist jedoch eine starke Vereinfachung. Die beste Schaltperformance erhält man durch die tiefstmögliche Position, bei der gerade noch der Käfig nicht das Kettenblatt berührt. Je niedriger Du den Umwerfer montierst, desto besser wird er schalten und desto weniger Mühe musst Du Dir mit dem Trimmen des Umwerfes geben.
====Nicht passende Umeerfer-/Kettenblattkombination====
To get the front derailer as low as possible, the curvature of the outer cage plate has to match the curvature of the largest chainwheel.<br>    If you use a larger chainring than the derailer was designed for, the rear of the cage will hit the teeth of the big chainring before the front of the cage gets low enough to provide crisp shifting without the need for trimming.<br>    If you use a smaller chainring than the derailer was designed for, it will shift OK, but you'll have to do a fair amount of trimming, due to the rear of the cage being higher than it should be, so that the chain crosses through it farther back.<br>    Lately I've started modifying front derailers for improved shifting with larger rings. I have a Shimano RSX front derailer on a bike with 50/38/28 Biopace (the sweep of a 50 Biopace is comparable to that of a 52 round.) The RSX front derailer works great on its intended 46/36/26 setup, but the cage doesn't match the curve of the larger chainring. In a couple of minutes with a grinding wheel, I removed a good bit of metal from the bottom rear of the outer cage plate, and a bit from the bridge section where the inner and outer cage plates connect at the back. This made the derailer match the curvature of the larger chainwheel, and allowed me to set it low enough to provide good chain control. This setup now works fine with an STI indexed shifter that doesn't permit "trimming" the front derailer.
====Die Begrenzungsschraube für den kleinsten Gang====
The low-gear limit stop stops the derailer from shifting past the smallest chainwheel and throwing the chain onto the bottom bracket shell. If the stop is too loose, the chain will fall off when you try to downshift to the small chainwheel. If too tight, you will find it difficult or impossible to shift down to the small chainwheel.<br>    On older front derailers, the low-gear stop is the one closer to the frame. Many newer designs reverse this position for reasons relating to the mechanism used.<br>    The basic adjustment for the low-gear stop is to set it so that the chain just barely clears the inner plate of the cage when the lowest gear (small front, large rear) is selected. This will usually be the best position for double-chainwheel setups, and will permit the use of most or all of the rear sprockets with a minimum of trimming.<br>    For triple chainwheels, it will sometimes be necessary to adjust the low-gear stop a bit looser, so that the outer plate of the derailer can travel far enough to knock the chain off of the middle ring.
;Kettenstopper
In some instances, you may find that one adjustment of the low-gear stop causes the chain to derail past the small chainring, but a tighter setting results in slow downshifting to the small ring.<br>    In such cases, a good, if inelegant, solution is sometimes to install an anti-derailment device that clamps to the seat tube. These products, such as the 3rd Eye Chain Watcher ® and the N-Gear Jump Stop ® set up a barrier preventing the chain from overshooting the small ring, no matter how loose the low-gear stop is set. This allows the low-gear stop to be set to allow the derailer to move farther inboard for faster, more precise shifting, even under some load. These devices can often save the day when extra-wide range gearing is used on a mountain bike or tandem.
====Die Begrenzungsschraube für den größten Gang====
The high-gear limit stop is pretty straightforward. It should be set so that the chain almost rubs on the outside plate of the front derailer cage when the bicycle is in its highest gear (large front/small rear). This will reduce the need for trimming as you shift the rear derailer.<br>    If the shift to the large chainwheel is slow, make sure that you aren't pedaling too hard: front upshifting requires being ready to have the cranks slow down when the shift takes place. If the shift is unreliable even when you are pedaling lightly, you may be able to improve it by loosening the high-gear stop a bit. If you do so, check to make sure that the derailer cage is not moving so far out that it can be struck by the crank as it goes by.<br>    Sometimes front upshifting may be improved by rebending the front edge of the inner cage plate outward a bit. This may be done with an adjustable wrench. This is rarely necessary on modern front derailers, but used to be a very common trick on older, cruder designs.


===Umwerfer trimmen===
===Umwerfer trimmen===
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