front derailleur replacement

RMichael

I need a replacement for my shimano acera front derailleur.
the exact model is FD-M390 and the bike is a 2012 GT Karakoram 2.0.
my budget is 30$ so i guess i can get something like a shimano SLX
I'd like some help in finding the exact model that will fit my bike (there are things like chainstay angle which i don't really understand :oops: ).
also, should i get it from EBAY or chainreactioncycles ?(which means the derailleur should cost 20$ because the shipping costs another 10...)

Thanks!

coulddobetter

You need to know a couple of things ...... diameter of the seat tube ( derailleur clamp will vary ) .where the cable enters the derailleur i.e top or bottom ( hence the term top or bottom pull ) ( photos show top pull ) number of front and rear gears it look s like 3 front 9 rear then measure the seat tube diameter where the existing derailleur is clamped and you have all the info you need for ordering .( a 3 x 9 front top pull derailleur with a clamp of the correct diameter ) ( clamps are often sized in a range so bare in mind they will obviously tighten as they clamp to the tube

Front derailleurs are pretty simple and tough . Are you sure you don't just need new cables and adjustment ?

The Rookie

Aftermarket Shimano mechs are all 34.9mm with shims for 31.8 and 28.6mm tubes, they are also dual pull, just leaving you to choose high or low mount or triple or double front ring.
Looking here
viewtopic.php?f=10004&t=12936627&p=18487540#p18487540
you want triple and low mount.

slindborg

Ahh I had that 390 mech... Managed to bend it into my top ring (fnaaaahhhh) last week.

I got the 772 deore xtr from wiggle as it was about the only top swing, top pull 34.9 9spd 44t compatible mech in stock at any of the main suppliers. About £22 job done.
Just fitted it this evening and I'm impressed how slick and smooth something as simple and agricultural as a font mech can be.

I now have upgradeitis and want a new rear mech

Giraffoto

slindborg wrote:

I now have upgradeitis and want a new rear mech

If your new front mech is an XTR and you have the urge to have your whole geartrain the same spec., it'll actually be cheaper to get a lower spec (Deore, SLX, XT) front mech and shifters/rear mech to match than to get XTR shifters and rear mech.

slindborg

Giraffoto wrote:

slindborg wrote:

I now have upgradeitis and want a new rear mech

If your new front mech is an XTR and you have the urge to have your whole geartrain the same spec., it'll actually be cheaper to get a lower spec (Deore, SLX, XT) front mech and shifters/rear mech to match than to get XTR shifters and rear mech.

The 772 is deore xt, not xtr.

RMichael

will a 10 speed derailleur work with my 9 speed drivetrain?
and also, does the chainstay angle matter? because there are derailleurs with an angle of 63-66deg and others with 66-69.

cooldad

Yes, although you may get a tiny bit of rubbing and yes.

RMichael

is it true that 63-66deg derailleurs are made for small frame sizes? (i read this somewhere).
right now i'm wondering whether to get the SLX (fd-m660) or XT (fd-m770), the SLX is 32$ and XT 44$ (on ebay)
is there any significant difference in shifting performance between the two that's worth the extra money?

thanks for your help!

slindborg

Just get a 772. Job done