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Front derailleur adjustment

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Front derailleur adjustment

Old 06-04-18, 02:41 PM
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kasmma
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Front derailleur adjustment

I am in the midst of switching my Trek 520 from bar end shifters to brifters. This is my first time replacing shifters or brakes.
I've gotten the brifters (Shimano Sora (3x9)) installed on the bike and threaded through cabling. The rear shifter works relatively well, could be a little smoother, but I can get to fine-tuning later. I'm really struggling with the front derailleur (Alivio down-pull). The derailleur worked fine with my bar end shifters, so, in principle, it should work here too, as I understand it.
Here's the symptom: I can get the chain to either successfully move between the smallest and medium chain ring or the medium and largest, but not across all three. As soon as I have enough cable tension to reach the largest chain ring, I am no longer able to shift down to the smallest chain ring. If I loosen it just enough to have it slip on to the smallest chain ring, I can't get it up to the largest chain ring anymore (and the chain rubs against the cage a ton)

Here's the latest iteration of my attempt:
  • To start - checked that the derailleur can travel the full distance between the small and large chain ring (so confirmed here that the high adjustment bolt is not preventing me from reaching the large chain ring)
  • Following Shimano's instructions for the Alivio...
    • With no tension on the cable, adjusted the lower adjustment bolt until I could hear a bit of rub between chain and cage on the inside (bike-side), then backed off just enough to no longer hear a rub
    • Applied tension to cable and tightened down the fixing bolt
    • Shifted to the middle chain ring
    • Adjusted tension in the cable with the barrel adjuster using same "do I hear rubbing?" method as above
    • Tried to shift onto the largest chain ring...a click, a twitch of the derailleur, but no success
At this stage, I was played around a bit - I was able to shift to the smallest chain ring and back to the middle no issue. When I tightened the barrel adjuster a bit further, I could get the chain to jump to the largest chain ring by cranking fast on the pedal, but it took a bunch of turns. Similarly, when I tried to shift into the smallest gear, I also had to crank quickly to get it to shift. When I then tightened the barrel adjuster even further, I could shift fine between the middle and large chain ring, but no success on getting to the smallest anymore - just a lot of rubbing on the derailleur cage.

I've tried reading around forums here, as well as following instructions from ParkTool and Art's Cyclery, but most of the instructions follow the above rubric or are very similar. So far all I've looked at has led to similar results. Does anyone have any ideas for what else I could try to make this shifting work? (Or have links to posts I might have missed in my searches?)

Thanks in advance for your help!
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Old 06-05-18, 12:39 PM
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Andrew R Stewart 
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The first thing I think of is the lack of intended compatibility between road and ATB when it concerns front systems. There's a reason why Trek speced the bar ends in the first place. This compatibility challenge continues to the ATB crankset that's been the OEM on the 520 for many years too. While the differences of cable pull/der movement per index point/chainring spacing are not large they do usually result in a system that sort of works but has chain rub in some/many combos.

So if I were the shop that did this to you I would want to talk about alternatives. Returning to bar ends, Using one of the thumb lever attachment conversions which locate the levers on or close to the brake blades. Swapping out the ft der and the crank/BB to road too. Swapping only the controls to x3 brifters but include a Shiftmate 7 adapterhttps://www.jtekengineering.com/shiftmate/shiftmate-compatibility-charts-choices/ . Andy
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Old 06-11-18, 12:21 PM
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Ooph. That's disappointing. I was advised by a friend who is a bike mechanic (from across an ocean), so no bike shop for me to go back to, unfortunately. I had read about the issue with road and MTB systems, but didn't realize that that which isn't road is MTB-ish. (And didn't do the deep compatibility check because of aforementioned friend.)

Thanks for the advice on options to go with to make things work - I'll take a look through them and figure out my next steps.
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Old 06-11-18, 12:36 PM
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It's not ideal but you can use a road triple front derailleur with that setup. It'll index correctly but won't be shaped perfectly for your rings--but a 48/36/26 crankset isn't too different from a 50/39/30 that, for example, current Sora 3x9 uses. You may have to run the FD a little higher than normal relative to the large chainring to get the inner cage to clear the middle chainring. There's also the IRD Alphina-D which is designed to index with a Shimano road triple shifter with a touring triple crank like yours.
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Old 06-11-18, 01:08 PM
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Actual front derailleur adjustments are placement; height , angle , and between limit screw stoke,

Everything else is problems with your STI shifter*, or the cables and housing.

*love friction shifters for their eliminating that, myself..



...
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