What front derailleur?
 

I've installed a SHIMANO DEORE FC-M590 48-36-26t MTB crankset on a touring frameset. I'm using Shimano bar-end shifters. The bike has 9 speed cassette & chain.

I've installed a Tiagra for triple front derailleur. The cage rubs on the big ring, even after loosening the high-gear limit stop screw.

Should I use a Deore MTB front derailleur? Will a MTB front derailleur work with a bar end shifter.

The nice thing about barend shifters is that, because they are friction for the front derailleur, they will shift nearly anything. So, yes, they will shift an MTB front derailleur.

BTW, I'm surprised the Tiagra fd won't swing far enough outboard. Are you sure the cable slack has nearly all been removed when the fd is in the granny position? Have you tried shifting the fd by hand with the cable detached to see if it will swing further?

Hi H-R

I'll reinstall the cable and try shifting by hand to see if I can eliminate the chain rub. I only need another mm.

Michael

Like HillRider said, try the easy stuff first. Removing all of the cable slack in the granny position may sound elementary, but you wouldn't be the first guy who overlooked that. Check how the cable attaches to the derailleur arm too. If your derailleur has a little tab on the back of the arm, the cable goes over that.

What's your rear dropout spacing? Mountain bike cranksets and BBs are generally designed to work with 135mm dropouts. If your spacing is narrower, you'll probably be able to use a shorter BB spindle. It's only a couple of millimeters difference, but that might be all that you need.

The Crankset is a Hollowtech II, so changing the BB is not an option.

If I go with a mountain front derailleur, which model?

M772 Low clamp, bottom swing 48t front chainring max

M773 High clamp, top swing 48t front chainring max

The model you choose depends on your frame as the clamp needs to fit the seattube where it is positioned and where the shift cable enters from. Some frames won't let you position the clamp very low as the seat tube flairs out near the bottom bracket shell.

No problem, the frame is steel and positioning the clamp is easy. The cable feeds under the BB shell. Do all of these derailleurs accept a road bike style cable feed?

I'm not that familiar with MTB front derailleurs but I do know some of them want the cable to enter from the top so be sure the model you choose will work with road-style cable routing.

Most current mountain bike front derailers work with either top pull or bottom pull cable routing.

With external bottom brackets, you can change the spacer behind the drive side cup to adjust the chainline. If you have 2 spacers on the drive side, try removing one spacer or you can get thinner spacers from your local shop for a couple of bucks. You can get them on-line but shipping will boost the price several fold.

Right now I'm using one spacer on each side, the Crankset came with 3 spacers. It's a 68mm wide BB shell, can I take the one spacer out from behind the BB cup on the drive side? Should I move it to the non-drive side to keep the spacing between the arms, or can I just remove it & forget it.

I'm starting to think that a MTB FD is my best solution.

Shimano, got one years, 10+, back made for 48t outers, MTBs were all 110-74 cranks then ,
have a 48,36,24 combo, [its on the winter studded tire bike now]
now thats called a Trekking crankset setup.
with compact/microdrive MTB being 44t outers, these days.

Yes and yes. I'm not sure about the new 10-speed stuff, but from experience, Deore 9-speed FDs designed for 44T top ring work fine with a 48T trekking crank and barends. In fact, I think they work better than road FD's because MTB FD's are designed to pull more cable, so friction-shifting the front is less touchy than with an FD designed for STI levers.

Shimano used to list an FD model specifically made for the 48T trekking crank, so that would be even better if you can find one. But good luck with that.

Those descriptions are somewhat contradictory. I think low clamp implies top swing, and high clamp implies bottom swing, but everyone seems to use different terminology, so who knows. This link gives a pretty good summary of the two major types:

http://www.bikeman.com/bicycle-repai...derailleur-101

You may also see different variants designed for different chainstay angles as well as top or bottom cable pull, though most FDs these days are "bi-puller", as someone already mentioned.

Since you already tried a Tiagra FD, and it fit on the seat tube and didn't overlap any bottle cage bosses, I would say trying the more traditional high-clamp style first is a reasonable guess. I had to go with a low-clamp design on my last build (involving a Nashbar touring frame) because my old FD's clamp ended up right on top of a bottle cage boss.

You may need to move the spacer from the drive side to the non-drive side since the spindle is a fixed length. You might also try a slightly thinner spacer. If you are only a little way away from not rubbing, a thinner spacer could move it just enough.

Before you tear things apart, take a look at the range of motion and alignment on the Tiagra. You said that the derailer rubs in the larger gear. Can you move the derailer outboard by hand? If so, then it's a cabling issue. Also check to see that the derailer is properly aligned with the crankset.

It looks like the SHIMANO XT M773 front derailluer is my best bet. It features a high clamp mount, bottom swing like the road derailleurs. The cage is shaped for a 48 or 44t chainring. The cable pull ratio is a better match for bar-ends in friction mode.

Edit: added content for more detail

Honestly, I'd go with a different model of Shimano or with a Sram X-7 (or X-9). The XT derailers suffer from the same problem as the high end road derailers. They are too sculpted which makes them futzy to set up.

The cage on the M773 is shaped for a 48t chainring.

The Tiagra FD might work, after all. The range of motion has increased. The cable attachment is the same, but the parallelogram arms are less stiff and easier to extend.