Front derailleur contacts the seat tube before it can drop my chain to the small chainring. Is there any trick to solve this apart from getting a longer bottom bracket?
by ggratty
Front derailleur contacts the seat tube before it can drop my chain to the small chainring. Is there any trick to solve this apart from getting a longer bottom bracket?
by ggratty
8 Comments
Get a wider bottom bracket.
It’s either a wider BB or grinding a way a part of your seat tube. You could *theoretically* shim the chainrings, but that would look horrible with that crankset.
Does it need to be that far over? Could adjusting the low limit help
Looks to me like the derailleur cage isn’t parallel to the chain and rings.
It seems very far up. Move it down so you have just a couple of mm between the derailleur and the top of the protective ring – you could even get rid of the protector and move the derailleur down even further. That way, you don’t try to shift with the bottom wider part of the derailleur.
Can you also route the cable on the dérailleur correctly?
Joining the chorus here:
1) It’s way too high. Kice the clamp down about 1cm or more. Usually the cage should be about 3-8mm above the chainring itself when it’s lined up.
2) it’s not parallel to the chainline. Rotate it so the tail and the nose of the outer cage are parallel to the chainline when it’s in the middle of the range.
3) adjust the low limit so it doesn’t contact the frame. This will also reduce chain drops.
4) make sure the clamp is tightened to spec and throw a very light coating of grease on the inside of the clamp to keep corrosion at bay.
Your derailleur is too high, so the wrong portion of the cage is hitting the chain. Reset it so that the bottom edge of the cage is 2 mm above the tallest tooth on your large chain ring when the cage is in the smallest chaining position.
Double check that when you pull it to the large ring, it still clears the large ring by at least 1 mm.
Reset the lower limit screw based on the chain position in the small chainring. Typically half a millimeter of clearance to the chain.
If you still have an issue with a hitting the frame before it will shift the chain into the small ring, then you need a longer bottom bracket so that your limit screws are set the derailleur positions farther away from the frame.
Hope that helps