Derailleur questions (XT)
 

Hey folks.

So I scored this in a parts bin today for $5. Some surface scratches and it's muddy, but all in all looks to be in great condition:

(Shimano Deore XT RD-M739)
http://i32.tinypic.com/ruz9ub.jpg

I ride a Surly Crosscheck (9-spd Tiagra) that I intend to change to a triple-crank up front, so I'll need the longer cage at the back that the XT offers eventually so here are my questions:

1. Is the XT derailleur compatible with my 9-speed cassette and indexed bar-ends?

2. With my current 2 ring crankset (and assuming the XT derailleur is in perfect working order), is it an upgrade over the new-ish Tiagra derailleur that is currently on there? Or would I be better off to wait 'til I get that triple up front?

3. Should I bother at all or just flip this part on CL/Ebay for now?

Thanks for your input!

I'd say:

1) Yes. I have an XT der on my wife's 9-speed otherwise Ultegra bike. Shifts beautifully, as well as the original road derailleur. If you're worried about longevity, put in a couple of pulleys with bearings rather than bushings.

2) Probably one step up from Tiagra - probably about equivalent to 105 from the 9-speed days.

3) Your call. Me, I'd do the replacement in a heartbeat if I needed the extra wrap and ability to handle larger cogs.

Sorry Charlie, but I think that is an 8 speed rear deraileur and won't work well with your 9 speed cassette and shifters. For confirmation, look it up or go to the Mountain bike or Mechanics forum.

robow you may be correct in this case, but I have had pretty good luck jumping between 8 and 9 speeds with the same rear derailleur. It is the shifter that governs the amount of indexing travel; the derailleur is just along for the ride. If the 8 and 9 speed cassettes are close to the same width, and the cogs are the same size; it seems like the durailleur should be able to handle the swing.

Incorrect.

The upper pulley *must* be a bushing to enable the pulley to shift laterally to align its self with the cog.
Even the latest XT RD's which have a little cartridge bearing in the lower pulley,
still use the ceramic bushing in the upper pulley for that reason.

It will probably work with a bearing in the upper pulley, but not as well.

Doug, not saying you can't make it work but it's not likely to shift as cleanly and IMO, not to be considered an upgrade.

Get a set of thumbies, set 'em to 'friction' and forget about indexing! Oooh I've come over all nostalgic...

Personally, I would keep it because it should have enough lateral movement to support 9sp plus some. I used the M735 (7sp generation) with a 9sp XT cassette without problems except there was rubbing when pedaling backwards on the 34T cog- I like to pedal backwards, but most people will likely not be pedaling backwards on the 34T. (The width of an 8sp and 9sp Shimano MTB cassette is very similiar, but the spacing between cogs is different.)

I've found these M739 (and M737) at bike swap meets occasionally for $10, and now I've got about 10 of them. The M739 also came in a shorter pivot bolt version.

The classic Bikepro webpage has an article on the M737 derailleur, http://www.bikepro.com/products/rear...tb_rrder.shtml, and the M739 originally retailed for about $42.99 (another link on the Bikepro webpage has prices), and works about as well as modern XT derailleurs costing more than twice as much.

-Lance

Update:

I figured I'd give it a trial run tonight and installed it.

Way more than enough lateral movement to work with my 9-speed and upon disassembling and cleaning you realize what a quality part it is. All the parts are rugged and well made, all with excellent threads.

Shifting seems great, took a bit more finesse to fine tune it than the newer derailleur but once I found the sweet spot I'd say it performs great.

I have to be honest though, I don't "feel" much of a difference between the modern Tiagra and the LX (mind you the LX is older). I'll probably keep riding it and keep the Tiagra as fall-back for the future.

Thanks for everyone's advice and please if you have any more input on Tiagra or LX derailleurs please share.

ryth,
Just curious if you have a 34 T in back because that's where I had trouble getting it to work cleanly?

Currently (although this will change soon) I'm still running the stock (non-touring) cassette. It's a Tiargra 9-speed 12-13-14-15-17-19-21-23-25t . Up front I have 36-48.

Fortunately I haven't hit any insane hills yet in my travels :innocent:

Yea, if you go to a larger 11-34 in the rear, you might have problems. I thought it was just my worthless mechanical and tuning skills but later on read that some others had the same difficulty. Hopefuly if needed, you can make it work.

When I swap out cassettes I'll let you know, probably won't be till spring however.

I have one of those RD's on my C'dale M700 with a largest cog of 32T.
I am pretty sure at the time those were mfg'd, 32T was the largest cog available.
So it wouldn't surprise me if they could not handle a 34T.