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New BB - can't shift front derailleur onto large chainring
I recently replaced my worn-out bottom bracket. I didn't have the part with me when I went to the bike shop, but I gave them the width of the bottom bracket when I ordered the part. The guy told me that this one was "slightly wider" but that it wouldn't matter.
After installing the new bottom bracket, I am having difficulty adjusting the front derailleur.
It appears that the derailleur is unable to move far enough out to properly shift the chain onto the large chainring. It is a 3-chainring mountain bike. Even if I pull the cable by hand and remove the H-limit screw, the derailleur does not move far enough out. It gets close, grinds a lot, and sometimes makes the shift.
My question is whether this means that the bottom bracket is simply too wide (it is only maybe a couple mm wider than the old one) and I should get a new bottom bracket or if my front derailleur somehow is faulty in that it can't shift far enough out?
The bike is 15+ years old so it wouldn't surprise me if the part were worn out.

To me it sounds as if the BB axle is indeed too wide. The front derailleur has a range it can move. If it was a narrow fit before you replaced it, it won't work now. And "a couple mm" can be quite a bit (as my colleague recently found out... here, the BB was too narrow, you live and learn...).

Yes you have the wrong BB for your bike.What you need if you still have the old one is take that to your LBS and have them order you the right one or you can order it your self at they don't cost that much. I hope you still have the old one to look at.or if you are sure it is only 2mm wider then get one that is 2mm smaller.Any way you have to get the right part or you will always have problem. I went back and re read your post I think the guy you talk to don't know much about bicycle if he told you it would not matter as you found out it does. Hope you get the right part soon and let us know the out come of it. But this is a good way for you to find out more about your bicycle we all learn some of us the hard way I sure have lean the hard way on a lot of stuff lol.
My dad always told me a Sledge a matic can fix any thing.

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