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Discussion Starter · #1 ·
To make a long story short: are there any disadvantages to using
a MTB rear derailler, XT for example, with a 9-speed 105 triple
crank (52/42/X) and front derailler, for normal road riding?

Here's why I'm asking:

I plan to modify my 9-speed 105 triple so that I can get up some
long steep hills, like Mount Washington, NH. Current plan is to
change the small chainring from 30t to 26t, and use an 11-34 MTB
cassette. I'm hoping to use this new setup for other road rides also.

I'd need the MTB rear derailler because the required chain wrap in
the planned setup is 49 teeth ((34-11) + (52-26)), which far exceeds
the rated 37t capacity of my current 105 long-cage derailler. Even
an XT long-cage rear derailler only has a 45t capacity, but I'm
hoping that's close enough.

Thanks for any comments.
 

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I see more of a problem with the front derailluer then with the rear. A Shimano triple front derailluer has a total capcity of 24 teeth between the large and small chainrings(large chainring-small chainring) You would be exceeding that by only 2 teeth. You may want to convert to a touring crankset (46/36/26 or 48/38/28) to accomidate the capcity you want.

That also depends on the bank account or finance commettee, better known as the wife.
 

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I wouldn't worry about chain wrap. You generally only use the granny ring with the largest two or three cogs so you're not very likely to ever get into the little/little combination. I'm a strong believer, by the way, in making sure that your chain is long enough to safely cover the big/big combination even though you aren't likely to use that one either.

Other than that, it'll shift just fine - at least on the rear. The only drawback I can see is the big steps between gears but that's more likely to be aggrivating on flat roads.
 

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it should work fine...

for years i've used an xt rear derailleur with road components for the same reasons you're working. through.
at first i used it with a shimano 600 double. i used an 11-34 and an 11-32 and an 11-30 rear mtb cassette. it worked fine.
the last year, i've used an xt rear derailleur with a 105 nine speed set up and with campy veloce 10 speed stuff. (i run it as a 9 speed. its a nice little setup that you can find out about online, if you're interested.) i run the same three cassettes with both. running mtb stuff works fine, from my experience. in fact, it definitely gives you more flexibility than road components.
also, i like sram chains and cassettes best. i've just had better luck with them. i've just had slight problems with shimano cassettes that i havent had with sram stuff.
 

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While we are on this subject, is a Deore XT front derailleur incompatible with STI shifters? I have 9-speed 105 STI shifters, XT RD, 11-32 cassette, 48/38/28 crank, and XT FD. The RD works perfectly but I cannot get the FD adjusted to where it it will shift between all three rings. I can get it to work well with only two rings. It seems like there isn't enough range of movement in the derailleur, and someone in the Bikes & Frames forum mentioned that this may be because of a compatibility issue between the XT front derailleur and STI shifters.

Any second opinions?
 

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Discussion Starter · #7 ·
Thanks

Thanks for the feedback, guys. Sounds like it'll work, so I may go
for it. I already have an SRAM PG-970 11-34 cassette. I'm looking
at a long cage "top normal" XT derailler, RD-M751-SGS. I'll see if it
works with 52/42/26 in the front - I'm not expecting very good shifting
between the two smaller rings, but I'll likely not be shifting out of the
granny during the bulk of the rides when I'll need the granny at all.
 

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I shall now answer my own question regarding the front derailleur, in case someone searches on this later:

I went to the LBS this morning and they looked up my question in their Shimano maintenance book. Indeed, the Deore LX and Deore XT front derailleurs are not recommended for use with road STI shifters. I have a Tiagra FD on order.
 

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Old, slow, and fat.
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Even better: make an XTegra (or 105Tegra) rear derailleur.

Pull the cage off the XT and mate it to the top of the Ultegra/105 derailleur.

Best of both worlds if you don't wanna buy a triple rear derailleur (and have an XT laying around like I did)

M
 

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MShaw said:
Even better: make an XTegra (or 105Tegra) rear derailleur.

Pull the cage off the XT and mate it to the top of the Ultegra/105 derailleur.

Best of both worlds if you don't wanna buy a triple rear derailleur (and have an XT laying around like I did)

M
I don't see how that could handle a 34 cog. The upper part of the 105 is rated at 27, will probably take a 30, but a 34??
 

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If you're going to run a 34 in the back I doubt that you'll want a 26 in the front, that would be a bit extreme. I'll bet a 30 X 34 will handle Mt Washington. I'd even try a 28 in the front but I think a 26 will be overkill.
A 12-34 cassette and XT rear derailleur would eliminate any chainwrap problems, especially if you stay with the 30 on the front.

Al
 

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Been using it for a year, NP

Sir Psychlo said:
Thanks for the feedback, guys. Sounds like it'll work, so I may go
for it. I already have an SRAM PG-970 11-34 cassette. I'm looking
at a long cage "top normal" XT derailler, RD-M751-SGS. I'll see if it
works with 52/42/26 in the front - I'm not expecting very good shifting
between the two smaller rings, but I'll likely not be shifting out of the
granny during the bulk of the rides when I'll need the granny at all.
I set up my Surly Cross Check for touring. Using an Ultegra triple crankset (now Truvativ Elita since it was cheaper than new rings), Dura Ace triple STI brifters, an Ultegra triple FD, an old school XT long cage rear (available from Jenson USA a few weeks ago and www.bikeman.com I think) and an 11-34 XT cassette. I did not go lower than a 30t granny. Be sure you use the correct BB. Worked flawlessly once I set it up. Still does and when the bike is loaded with stuff, it's appreciated.

When this stuff was on the road bike for Mt Washington, I had that Ultegra crank with a 24t granny and the Ultegra deraileur. Shifting from 24 to 42 worked fine, a bit slow but it works. I had a 12-27 in the back and an Ultegra long cage.

It'll work.
 

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Al1943 said:
I don't see how that could handle a 34 cog. The upper part of the 105 is rated at 27, will probably take a 30, but a 34??
What's the upper got to do with how much chain the cage wraps? The pivots are in the same spot, right?

Basically, doing what I suggested is a looks thing.

M
 
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