OK,1st I am a newb as far as parts and repairs...so,here goes...
I need a new front derailleur and am wanting to order 1 online,and get the LBS to put it on for me.How do I determine exactly which one will fit? I chatted with a tech at the LBS and he asked if mine was top pull(and it is) and the diameter of the tube? I mean seems that there are quite a few things to consider,but perhaps Im over thinking it.Any help will be appreciated as Im gonna try to find something on sale or clearance to fit my bike.

https://www.jamisbikes.com/canada/the...gro1_spec.html

If you have a Sram X3 Front Derailleur as the bike in the link does, then it is compatible with top and bottom pull frames.
The frame you have is set up for a bottom pull derailleur not a top pull derailleur.
Some derailleurs can be used as either top pull or bottom pull, some derailleurs can only be used as top pull, some derailleurs can only be used as bottom pull.
Derailleurs can have different swings too, they can be top swing or bottom swing.


What's wrong with your current derailleur ?

Why not get your LBS to get you one, and fit, you don't seem to know what size / type you need and can't fit yourself, they can get this right for you, and you will make more friends with your LBS in giving them some trade, rather that buying at the cheapest price and getting them to fit, they will probably charge you the max they can for fitting if you don't buy the part from them.

If you're going to have the bike shop install the FD, have them figure out which is the right one to order. FD's are so cheap you won't save much money trying to order it yourself, given shipping, but you will be responsible for any errors/defects if you do so. Just have the bike shop order one and install it, then any problems are their responsibility.

I agree that it is bad karma to order discount parts online and then expect the LBS to get it to work for you. I have at times gone to the LBS and had them help me decide which component was right for me and then checked out the prices online, but if I order online, I always install them myself, never at the LBS. More often than not, the prices at the LBS have been comparable to the online plus shipping. If the difference is 10% or less, I usually order from the LBS just for the good will. Sometimes they will even match price as they make more money on the labor than on the markup. A good LBS knows that a $5-$10 discount on a part today can translate into years of customer loyalty and lots of good word of mouth publicity. Excessive haggling can get you labeled as "cheap" but it never hurts to make a simple request for a price match.

Front derailleur selection can get crazy. Seat tube diameter, top pull vs. bottom pull, top swing vs. bottom swing, road vs. mountain, and I'm not sertain that I haven't missed one. Picking the wrong one can grab you in ways that you don't expect. The clamp needs to go where the bottle mount is located, or where the seat tube flares. The arc of the derailleur doesn't match your chainring.

One of the nice things about buying a front derailleur through your LBS is that they take the risk of ordering the wrong thing.

OK,I get it...order from the LBS As far as whats wrong with it?Technically nothing,however sense day one have had problems with either A-Chain rub+hard to go into 3 on the chainset+chain coming off sometimes when going into 1....or B-Chain rub+goes into 3 most of the time+hard to go into 1...Now when I got it I had these problems and I tryed to adjust.I couldnt do it,took it to 1 LBS,they adjusted and said that my front derailleur was the problem(cheap) and I needed to replace it w/a better product.(I thought they were just trying to make a sale) Then took it to another LBS with a great rep,they adjusted it,and seemed good,still experiencing chain rub,but shifting seemed better...for about 2 days,then right back to the way it was.As I have looked into this derailleur I have discovered a few reviews saying the same thing I have been experiencing.Now why would sram put on an inferior derailleur is beyond me?...Also one review suggested the "X"models were designed to only work with a maximum number teeth of only 48,and mine has 52 which would explain a lot.