[BruceBrown]

I've searched the threads enough and found some good posts from 4 years ago on choosing a light front derailleur for a 2 x 9 set up. I just got a new Niner JET 9 XL size frame and need to get a lighter derailleur.

Now, for the moment, remove the irony of building a weight weenie 29"er full suspension bike. My idea of weight weenie success will be if I end up in the 22.x - 24.x lb range. On paper I'm there, but that's on paper. And keep in mind this is a size XL full suspension XC race bike in the 29"er wheel size.

Back to the derailleur...

Niner recommends the XT M771 in 34.9 clamp, bottom pull, bottom swing (traditional) due to some clearance issues, blah, blah, blah. Again, I'll be running 2 x 9 with 27T/40T rings on 180mm Race Face Turbines - square taper so I can really dial in my chainline and Q-factor.

I've got the Shimano XT M761 traditional in dual pull that I was running on my Sugar, but it is a porky pig at 178g!!! The question is, and I believe Nino raised this issue back in a thread I just read from 2004, can one run a Dura Ace double on a full suspension frame? Would a triple be better?

As you can see in the photographs, the swing arm and clearance issues noted by Niner. The new XT M771 is a design that takes clearance issues into account:

Increased tire clearance through modified cage tail shape. More clearance behind the seat tube for down swing FD, mud guard, or suspension. With front SIS, Dual Pull, Multi Clamp Band, and Offset Adjust Bolt.



But before I hit the buy button, I just wanted to think it through to see if there are other, lighter options. XTR, Dura Ace, etc...

Here's a shot of my porky pig M761 mounted on the frame with an example of a 2 x 9 crank (not the one I'll be running, but one from my parts bin):

(cable is not hooked up, so the cage is sitting way in in the "limp" position)



Another angle...



Profile...



It sounds like the latest XT mountain FD's would save me 20 - 40g over my older XT, but if I'm going to buy a new derailleur I might as well shed some more. That's why I am wondering about the Dura Ace. I'll be running a SRAM Twist to trim the front derailleur for the best shifting.

Any suggestions on a 34.9 clamp, bottom pull, bottom swing light derailleur that would work on this JET 9?

Thanks.

 

[Tiffster]

You could run a Sram Red front derr.

Im running one on my full suss. 86 grams, awesome shifting and the cage has an odd profile in that it is slighty bent outwards which should take care of any clearance issues.

As your frame is bottom pull you wont need to modify it for top pull which is a bonus.

Dura Ace double will work too - as your using gripshift you can trim it out to stop rubbing (although my Sram Red doesnt rub in any combination)

So it's up to you, either will work.

 

[nino]

Dura Ace will work...

4 years ago i was always suggesting the "old" 9s FD-7700 derailleur. this one will work also with triple rings up front. now you use only 2 rings so go ahead and get the newer FD-7800 from the 10s group.

with the integrated 34,9mm clamp it weighs just 78g. i don't see any clearance issues and it also has bottom pull...should install in minutes and works great too.

 

[BruceBrown]

4 years ago i was always suggesting the "old" 9s FD-7700 derailleur. this one will work also with triple rings up front. now you use only 2 rings so go ahead and get the newer FD-7800 from the 10s group.

with the integrated 34,9mm clamp it weighs just 78g. i don't see any clearance issues and it also has bottom pull...should install in minutes and works great too.

Thanks Tiffster and Nino. Obviously, I am excited about dropping down from 178g to the 78-85g range for the front mechanical.

BB

 

[Broccoli]

I use SLX double (665) front derailleur on my AM bike, and it works great with 22-36 gap, but I do not think it can be used with 44 or 42. Short cage..

 

[BruceBrown]

I use SLX double (665) front derailleur on my AM bike, and it works great with 22-36 gap, but I do not think it can be used with 44 or 42. Short cage..

Looks good, but won't work with my need for a bottom swing 27T/40T combo according to the specs:

It can accommodate a maximum chainring size of 36 teeth.

The Shimano FD-M665 SLX front derailleur is Top-Swing and Dual Pull so it can run in harmony with all types of cable routing.

 

[Broccoli]

Looks good, but won't work with my need for a bottom swing 27T/40T combo according to the specs:
It can accommodate a maximum chainring size of 36 teeth.

You should try, Shimano is usually very conservative about capacities. It definitely shifts better for a larger gap on the SLX double.. Also depends on the chainline, this is for granny/middle. There is the Saint double, designed for 83bb, so it will accommodate wider chainline, that may be an option.

 

[Tiffster]

Not to mention SLX will probably be heavier than the current XT on you have.

 

[Broccoli]

Not to mention SLX will probably be heavier than the current XT on you have.

Downswing SLX double is 142g, current XT is 155g.

 

[BruceBrown]

Downswing SLX double is 142g, current XT is 155g.

Both of which are lighter than my older XT 761.

As long as I'm spending, I'm going Dura Ace and welcoming the shaved additional grams.

BB

 

[Broccoli]

As long as I'm spending, I'm going Dura Ace and welcoming the shaved additional grams.

That makes sense. SLX and Saint chainlines are really for the AM cranksets with a bashguard. They work very well in that application though.