Shimano Nexave Front derailleur FD-T401
The Nexave 400 series front derailleur is made to work with a triple crankset and is designed to work with a large chainring of 46 or 48 teeth for optimal shifting , the middle chain ring needs to be at least 10 teeth smaller then the large ring , and the small ring should not be smaller then 20 teeth of the large rings size , here are couple examples of combos are a match , 48-38-28 or 46-36-26 etc.
Nexave is Shimano’s dedicated Hybrid / Cross / Trekking / Urban Parts kit , there where four different quality levels of parts available that used the Nexave label ,The derailleur’s where available in the USA from the mid 1990s to 2006 (Shimano still produces them for other world markets).
This derailleur is compatible shimano mtn shifters , Sram trigger or grip shifters and shimano bar-con levers , they will not shift properly if you try to use them with Shimano road STI shift levers .
Here are the four Nexave levels of quality and their equivalent levels of quality in Shimanos mountain line up , higher quality derailleurs generally are made of harder alloys and have a longer wear life .
Nexave 600 series = Deore XT
Nexave 400 series = Deore
Nexave 300 series = Alivo
Nexave 200 series = Altus
The 600 series was designed for 9 speed systems or bicycles with 27 gears
The 400,300,200 series was designed for 7-8 speed systems or bicycles with 21or 24 gears
This FD-T401 (400 series) derailleur has a clamp size of 34.9 mm or 1-3/8 in , you can clamp this to the other two smaller sizes of 31.8mm and 28.6mm if you have derailleur clamp shims , they are not included with this derailleur but are available at most bicycle stores . the derailleur is top pull , this means that the cable is pulled from the top of the bicycle .
These are great choice for fixing or putting together hybrid or touring bicycles , also many older mtn bikes used larger chainring combos especially previous to 1993 and these derailleurs will work with older five and six speed drivetrains .
Shimano tech documents for this derailleur are at http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Nexave/FrontDriveSystem/F570C_EN_v1_m56577569830605628.pdf