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That ad is for a top swing derailleur (also called low clamp). A bottom swing (aka high clamp) would have the clamp mounted above the derailleur like this


Bottom pull refers to a derailleur that must be activated by a cable that runs from under the bottom bracket. Top pull means the cable must run down the seat tube and into the derailleur. Dual pull means any cable set up will work.

The Mission uses top swing, bottom pull (or dual pull), 34.9mm clamp.

The XT in the ad says 31.8 clamp. If that's true, it will be too small. However, most derailleurs are built with a 34.9 clamp and come with a reducer shim to fit bikes with a 31.8mm seat tube.. So ask this seller if his derailleur is really 31.8 or if he's been using the adapter to make it that size.

Before you buy a used derailleur, make sure there's no play. FDs get loose with age and eventually start to rattle...
 

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Discussion Starter · #4 ·
Does it have to be a shimano since I have shimano shifters or can I mix sram derailleurs with shimano


is there a difference in derailleurs between road bikes and mtb?

If I went to the shop I may get the lower end stuff.. Due to the economy (for me anyways)
 

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You can use a Sram front derailleur with a Shimano shifter. Both brands use the same cable pull for the front.

This is not true for rear derailleurs. Sram uses 1:1 vs Shimano's 2:1 cable actuation.

I think most Sram front derailleurs are top clamp / bottom swing though.
 

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SRAM and Shimano front derailleurs are interchangeable. SRAM currently makes all their derailleurs with low clamp option, and the X5/X7 are both dual pull. I personally prefer SRAM because I think they hold up a bit longer, but there's not a major difference. Get whatever is cheaper. I'm running a Shimano SLX 2 speed FD these days to match my SLX double chainring + bash crankset.

I've never seen a low clamp road FD, so I don't think that will work. Anyways, I'd expect a road derailleur to be less durable than a beefed-up MTB design at the same price level. There's also a chance of having clearance issues. Road bike cranksets run big chainrings (50T+) and the FD will be designed to handle that instead of maximizing clearance as the suspension cycles. Bottom line: don't bother with a road derailleur.

I'd recommend a Shimano Deore, SLX, SRAM X5, or X7. The higher end stuff will be lighter and not much else. I've personally used the Deore and X7 in the past on my Mission, and both worked well.
 

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Discussion Starter · #7 ·
Thanks guys.. I just ordered a FD-m660 slx.

At a great price to hoot.. 20.29 shipped new.
 

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Right on :thumbsup:. Are you all set to install it yourself? Park Tools; website has a great step-by-step procedure.
 
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