View Single Post
Old 04-09-15 | 08:32 AM
  #2  
Phil_gretz's Avatar
Phil_gretz
Zip tie Karen
 
Joined: Aug 2009
Posts: 7,005
Likes: 1,546
From: Fair Oaks Ranch, TX

Bikes: '13 Motobecane Fantom29 HT, '16 Motobecane Turino Pro Disc, '18 Velobuild VB-R-022, '21 Tsunami SNM-100

Okay. Well, now you'll start from the beginning. Is the chain on the bicycle? If not, remove and thoroughly clean the front derailleur, then lubricate all of the pivot points. While you're handling it, notice how the two adjustment screws are labeled "H" and "L", for setting high and low limits. These screws make contact with a cam that defines the motion of the derailleur cage from its base. One on each extreme of the cam's movement.

Re-mount the derailleur, paying attention to align the main axis of the cage parallel to the chainrings. Height should be so that the cage (when swung outward) clears the large chainring by ~3 mm or so.

High is 'normally' on the large chainring, and limits the outer most motion of the derailleur cage while under cable tension from your front shifter. Low is 'normally' on the small chainring, and limits the inward movement of the cage, which you've described as "towards the frame" once you undid the cable.

You begin with the Low screw. Chain back in place, and on the inner chainring and rear innermost (lowest) cog. Begin to tighten the L screw and watch the cage move outward, until the inner edge of the cage (that contains the chain) just makes contact with the inner edge of the chain. Back it off until there's 0.5mm or so between the cage and the chain.

Shift down to the smallest (high) cog on the rear.

Now attach the shift cable. Make certain that it moves freely through its cable and guides, and that your shifter is in the "lowest" or most slack position. Pull the cable somewhat taught, paying particular attention to the binding bolt area. If there's a small metal tab just before the bolt, then make sure that the cable passes OVER that tab before clamping it.

Shift the front onto the front chainring. Note the position of the cage's outer edge and the chain. Cage too far? Then tighten the "H" screw until it limits the movement of the cage to within 0.5mm or so of the chain.

Unable to shift upward to the large chainring? The derailleur cam may be blocked by the "H" screw being too tight. Back the "H" screw off and watch the movement of the cage/cam as you attempt to shift.

There will also be a technical note on your particular derailleur, if you get the model # from the edge of the cage. Search technical documents and that model number. There will be diagrams.

Good luck. PG
Phil_gretz is offline  
Reply