# Direct Mount Front Derailleur



## DavidR1 (Jul 7, 2008)

What are the advantages and disadvantages of direct mount? Thinking of having one of these put on my custom build.


----------



## Walt (Jan 23, 2004)

*DM is great*

Advantages:
-No need for the seat tube to be in any particular location relative to the BB - ie, you can offset/curve/kink/interrupt the seat tube. E-types allow this too, but they're not with all crank systems, and their shifting perfomance kinda blows. 
-Easy to set up for any chainline by moving the mount in/out (ie, you can put the mount wherever it needs to be for even a Fatbike). 
-Stiffer/more secure mounting than clamp-on or e-type. In theory, this means better front shifting. In practice, well, it's a front derailleur, so it basically still sucks, but it sucks a little less. 
-The derailleurs themselves are a little lighter. The mount makes up the difference, though.

Disadvantages:
-Currently there are multiple mounting point standards. IMO the Shimano ("high direct mount") one-bolt system is the best but who knows which one will end up being the betamax of front derailleurs. 
-You might be able to make an argument that you could damage your frame if you pedal a broken link through the cage and tear it off the bike. If you destroy the mounting threads, you'd need to do some fairly involved/annoying repairs, potentially. 
-If you decide not to run the front derailleur anymore, the mount may not appeal to you aesthetically.

-Walt


----------



## TrailMaker (Sep 16, 2007)

Just in case...

You had not considered it, I might offer the Problem Solver direct mount fixture. Best of both worlds, perhaps? If you no likey or it no workie, you can just take it off. Tweakable too!


----------



## Blaster1200 (Feb 20, 2004)

I'm surprised Walt didn't mention it, and he was the one who turned me on to it, but the biggest advantage for the high DM for me is that it allows the most clearance for short chainstays on 29ers. No other mtb derailleur comes close, from what I've seen.


----------



## fanzy4 (Aug 19, 2004)

One thing that might be a disadvantage: the small range of vertical adjustment. If you place it at the correct position for a double crankset (like a 32/20 on a 29er), you won't be able to move to a triple (with 42T ring).


----------



## DavidR1 (Jul 7, 2008)

Blaster1200 said:


> I'm surprised Walt didn't mention it, and he was the one who turned me on to it, but the biggest advantage for the high DM for me is that it allows the most clearance for short chainstays on 29ers. No other mtb derailleur comes close, from what I've seen.


This is the reason we are thinking of going to dm.


----------



## Walt (Jan 23, 2004)

*Good point*

That's what I was trying to say when I mentioned the seat tube stuff, but I should have made it more explicit.

OP - if you look at the 29er forum archives, you can find a super-sweet AM 29er that Blaster1200 just built with a DM derailleur. Definitely a geometry that would be impossible with any other front shifting setup. I'm too lazy to look up the link, maybe Blaster can post it?

-Walt



Blaster1200 said:


> I'm surprised Walt didn't mention it, and he was the one who turned me on to it, but the biggest advantage for the high DM for me is that it allows the most clearance for short chainstays on 29ers. No other mtb derailleur comes close, from what I've seen.


----------



## Walt (Jan 23, 2004)

*Not an issue*

They actually have a huge range (probably almost 2cm?) of adjustment now. And they make several double-specific short-cage ones (which, btw, kick serious ass) as well. As long as you have a vaguely appropriate derailleur for your gearing, you're good to go.

The first generation only had about 5mm of adjustment and only came in one version, but that was 2010... this is now. 

-Walt



fanzy4 said:


> One thing that might be a disadvantage: the small range of vertical adjustment. If you place it at the correct position for a double crankset (like a 32/20 on a 29er), you won't be able to move to a triple (with 42T ring).


----------



## Blaster1200 (Feb 20, 2004)

fanzy4 said:


> One thing that might be a disadvantage: the small range of vertical adjustment. If you place it at the correct position for a double crankset (like a 32/20 on a 29er), you won't be able to move to a triple (with 42T ring).


The Shimano direct mount derailleurs are specific for double or triple cranksets - you buy the derailleur to match your cranks.

Except in the case of a double 32/20 (did you mean 22 or 24, of which Shimano offers?) where you use a triple derailleur mounted in the normal position for a triple crank. If you're doing goofy stuff like a 32/20 that's out of Shimano's design spec, you're on your own, anyway.


----------



## Blaster1200 (Feb 20, 2004)

Thanks Walt. http://forums.mtbr.com/29er-bikes/west-coast-am-hardtail-760939.html


----------



## fanzy4 (Aug 19, 2004)

Walt said:


> They actually have a huge range (probably almost 2cm?) of adjustment now. And they make several double-specific short-cage ones (which, btw, kick serious ass) as well. As long as you have a vaguely appropriate derailleur for your gearing, you're good to go.
> 
> The first generation only had about 5mm of adjustment and only came in one version, but that was 2010... this is now.
> 
> -Walt


Thanks for the update ! When I built my frame the DM version (XT or SLX) was only available with a triple cage (and 5mm of adjustment...).


----------



## pvd (Jan 4, 2006)

One great reason for doing a DM with Shimano is the self contained cable stop. It's so much nicer than needing a stop on the frame.


----------

