Bicycle Mechanics - Question regarding Front Derailer, sequel to Question regarding Cranks :)

Well I took someone's good advice from here and bought a narrower bottom bracket, that worked well and now the cranks are where they should be. However I now have a different problem. There is no way that I can see to get the front derailer to shift into the big ring, it will only go far enough to make the chain rub but not catch. I have taken the limit screws out, so that isn't the problem, I've played around with the mounting for the derailer, moving it up and down obviously dosen't help. What is wrong with it, do I need a new derailer that has a wider shift range or what?

do I need a new derailer that has a wider shift range or what?


possibly, it's hard to tell without looking at the bike (imo) however if you made the bottom bracket narrower, then the cranks should be closer to the frame, so the derailleur should still work, although if you have taken the correct limit screw all the way out, then it appears as though you are at the limit. :rolleyes:

you could purchase a front derailleur which is designed for a triple crankset, and would have a wider range....

Yeah the old crankset was also a triple, so it should still work, but it dosen't.

lube/wax might help... or tighten the cables

By chance do you have a braze-on clamp holding this derailleur on???

Yeah, like tFUnk said, check the Front cable tension. Is it real loose when in granny? Also, maybe try turning the front of the derailleur outward a tad. that might help push the chain onto the big ring.

You tried up and down, but did you try twisting it? Sometimes a little angle is all you need.

hi man I had same problem as you did. the spindle length of my bike is 126mm and the current front deraileur works well. I tried to change my crank set to a new shimano one which I think only takes 110-113mm spindle, then I came up the same problem as yours, the deraileuo does not go to the outer chain ring, I still wonder that if I change BB and get the 110-113 spindle length, then the front deraileur will work? still wonder

That's exactly what the problem is. That's what I did, I also tryed everything you guys mentioned, nothing seemed to work.

If you can, post a pic. Are the chainrings the same size (# of teeth)? What type of shifters do you have?

You tried up and down, but did you try twisting it? Sometimes a little angle is all you need.

DUDE! Wrong forum! :p

Sorry can't post a pic, but the shifters are cheap 8spd Rapid Fire, and the new crank has the same number of teeth as the old one. By the way the bike is a 2002 Trek 4300.

Question, when you are trying to shift into the big ring, where is the chain on the rear cassett? If you are in the big cogs in back it could cause the chain not to engage the big ring do to the alignment.

Another thing, when you swapped the cranks, did you loosen the derailer? If you did, check to be sure all the cable housing is still in the mounts on the frame. Some times it will slip out causing to much slack.

DUDE! Wrong forum!

LMAO :roflmao:

I think dirt might be onto something here. When you shift to the small ring is there slack in the cable? If so, that would be the problem. The shifter can't pull the derailer enought to move to the big ring. Try tightening the cable.

Finally swallowed my pride and went to my LBS to see what the problem was. Turns out nothing is wrong with the derailer, they gave me the wrong size bottom bracket. So because they screwed up the mechanic gave me a $90 XTR bottom bracket in exchange for the $35 one that they had given me the day before. So needless to say I'm happy, the bike works awesome now, I tweaked my brakes and rear derailer into adjustment so now it's ready to role with pretty much an entirely new drivetrain. Anyway, Thanks to everyone for all the helpful advice.