My front derailleur is broken. The front derailleur is of the shimano group Nexave, which apparently they don't produce anymore. I am trying to find out which type I should buy that is compatible with my shifter. My shifter is a Shimano Deore SLM570. I now bought a Shimano Tiagra FD-4703-B front derailleur, but I don't want to unpack it before I now it will be compatible (since I can't bring it back anymore once I unpack). I tried searching on the website of shimano itself (https://productinfo.shimano.com/en/compatibility), but I can't find the specific type of shifters I have (i.e. SLM570). Is this type also very old and is that why I can't find it? Any help would be much appreciated! Thanks a lot in advance.
1 Answer
In the 2005 Specifications list on the Shimano technical documents, one finds that the SL-M570 is a Deore LX model (LX is no longer made either) from the mountain 9 speed rear class. The front shifter is a triple (2 clicks moving the chain along a triple chainwheel crankset). One can also see the M570 front derailleur is used on a triple crankset with the largest chainwheel being 44 teeth. Is your large chainwheel 44 teeth?
The size of your largest chainwheel is important as the front derailleur's cage must closely follow the contour of the large chainring. The FD-4703, while designed for a triple chainring is designed for a 50 tooth large chainring and an 11 tooth difference between the large and middle ring. Also, it's designed for a 45mm chain line and most mountain cranksets are 48.5-50mm. See the FD-R4703 Specs here. Thus, if your current large chainring is smaller than that, the FD-R4703 is not the optimum choice of front derailleur.
One positive here is that with front derailleurs, most all have the same actuation ratio. This means that many models will respond correctly to many models of front shifter input. Your best bet is to find a mountain 9 speed front derailleur that has a band clamp (ease of use and broad compatibility with bike frames), is designed for the amount of teeth of your large ring, and is a triple front derailleur (designed for 3 chainwheel set-ups. You'll also want to pay attention to chainline compatibility. Front chainline is measured from the center of the bottom bracket shell to the tips of the teeth of the middle chainring of a triple. As mentioned, most mountain triples will have 48.5-50mm chainline. A mountain triple front derailleur marketed as 8,9 or 10 speed will work given the large chainring size and chainline are accounted for in its specs.
