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  1. #1
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    Front derailleur help

    I picked up a used bike with some nice components (SRAM X-0 shifters and Shimano XTR front derailleur) and I'm trying to learn to work on some of the mechanics. I was getting some chain rub so I'm trying to adjust the front derailleur. As I read all of the guides I have a question that doesn't seem to be addressed

    If I want to start over with the front derailleur set up, how should my set screws be set? They appear to both be screwed in all the way. When I release the tension on the cable, the front derailleur moves very far toward the frame. Some tutorials I've seen say to use the L set screw to set the inner limit with the cable loosened, but mine won't get anywhere near the smallest chainring. Maybe I'm missing something? Any help would be greatly appreciated. I'd really just like to be able to set everything to a neutral position so I could start fresh.

    Sent from my LG-H820 using Tapatalk

  2. #2
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    There are two limit screws, a high and low. As you might guess, the "H" screw limits the outboard travel of the derailleur and the "L" screw limits the inboard travel. The derailleur also has to be properly aligned. The outboard cage should generally be parallel to the chainring teeth. The height of the derailleur should be set so that it clears the teeth of the biggest chain ring with 1-2mm of space. Also confirm that the cable and housing are in good condition and properly sized. Additionally make sure the derailleur cage is not bent. Are the shifter and FD both either 2x or 3x? Mixing them can cause weirdness.

    Assuming the derailleur is aligned and the height is correct loosen the "L" screw so the chain drops cleanly onto the smallest chainring. Next loosen the "H" screw so the chain moves cleanly to the largest chainring without dropping off on the outboard side. If the chain won't drop onto the smallest ring despite loosening the "L" screw look into the derailleur at where the screw contacts the stop. If the the screw is not touching the stop, the cable is too tight and you must loosen it. If the screw is in the stop, loosen it until the chain drops cleanly onto the smallest cog. Similarly if the chain won't move cleanly to the largest chainring check if the "H" screw is touching the stop. If it's not, the cable is too loose. If the screw is on the stop loosen the "H" screw until the chain moves cleanly onto the the largest chainring.

    Once the high and low limit screws are more or less set, adjustment is through cable tension via the barrel adjuster at the shifter. You may still need to make slight adjustments of the limit screws. When dialing in cable tension or limit screws, make small adjustments at a time. Remember too that the chain angle changes drastically when shifting on the cassette. A chain that doesn't rub the FD on one cog may rub when the chain is on another cog. Run through the whole cassette. Setting the FD is a lot of trial and error.

    Pics of your setup might help if this description doesn't help you. You can also look at the Park Tool website; they usually have good info. From your description, if the limit screws are indeed screwed all the way down, the FD should move very little or not at all. You can look inside the FD and see whether the limit screws on the stop. I also don't see how the FD could move very much toward the frame and the chain not drop onto the smallest cog, particularly if everything is in good condition and the FD properly aligned.

  3. #3
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    "The outboard cage should generally be parallel to the chainring*teeth."

    This is where I'm having trouble. When I loosen the cable bolt, my cage is a good amount inside the teeth of the smallest chainring.

    Sent from my LG-H820 using Tapatalk

  4. #4
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    Quote Originally Posted by llcamino View Post
    "The outboard cage should generally be parallel to the chainring*teeth."

    This is where I'm having trouble. When I loosen the cable bolt, my cage is a good amount inside the teeth of the smallest chainring.

    Sent from my LG-H820 using Tapatalk
    Those are different issues. If the cable is loose, and the cage is "inside" the teeth of the smallest chainring (I assume that means between the chainring and the frame) then the low limit screw needs to be tightened. The FD default position, meaning without any cable tension is toward the bike frame. Screw in the low limit screw until the FD is more or less centered over the smallest chainring teeth. Next, push the cage with your hand to the high position. If the cage won't reach the biggest chainring teeth, loosen the high limit screw until it does. Make sure the shifter is set for the smallest chainring. Allow the FD cage to rest and attach the cable. There should be no slack. The barrel adjuster at the shifter should be unscrewed about 1/2 way before attaching the cable to allow adjustment later on. Now fine tune the adjustment running through all the gears.

    By parallel, I'm referring to the orientation of the outer cage plane relative to the chainring teeth plane. Picture a horizontal line running through the outer FD cage from front to back. Now picture another horizontal line tangent to the chainring and running in the same direction (front to back). Those two imaginary lines should be parallel.

    If I'm not explaining this well, or you still can't get the FD working pics would help.

  5. #5
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    Thanks for the replies. Your explanations make perfect sense. However, its still the first part that is the problem. The default position of the cage is inside of the smallest chainring (closer to frame). And the low limit screw is screwed all the way in. I can not get the cage to move outward (away from the frame) so that it lines up over the small ring teeth using the limit screws. Only by manually pulling on the cage.
    To answer an earlier question, everything is set for a 3 x 9 set up. I many need to adjust the height a little (maybe lower by 1mm) but I don't think that is causing the issue. I could possibly load pics later.

    I think the explanations for everything else make sense, I just can't get past step 1 of using the low limit screw to get the cage over the smallest ring with no cable tension.

    Hopefully I was able to explain it a little better that time.

    Sent from my LG-H820 using Tapatalk

  6. #6
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    Quote Originally Posted by llcamino View Post
    I can not get the cage to move outward (away from the frame) so that it lines up over the small ring teeth using the limit screws. Only by manually pulling on the cage.
    If the usual way doesn't work try another approach. Back off the low limit screw and pull the cable through until the derailleur gets to the same the position you achieve by manually pulling it. Then adjust the limit screw to just clear the inside of the smallest chain ring.

    Pictures would help.

    Tim

  7. #7
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    Ok. I'll try that. I just took it for a ride. My "time away from family messing with the bike" was better used riding today. I got minimal chainrub, but I'm missing some gear combinations. Ones that I don't need (large and large) but I think I have some bike OCD where I feel like it should all be flawless. I'll try the new approach in a few days and report back.

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  8. #8
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    Without visuals, I'm at a loss at this point other than that it sounds like the cage is not properly aligned. Bear in mind too there are times when fudging the cage angle is necessary to really dial in the FD. 3x drivetrains can be tough to dial in. The change in chain angle as it moves across the cassette is greater than the wide of the cage.

    If all else fails, you can be sure to fix it if you get a narrow/wide chainring and just go 1x. I ran 1x9 for many years. If you need more range, 1x11 is an easy conversion and prices have come way down, though it's not nothing. Otherwise bring it to a shop and stop banging your head against the bike frame.

  9. #9
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    I finally made some progress. As it turns out, the Limit screws were not all the way in. They felt like it because the spring of the derailleur was strong which caused the L screw to be extremely tight, making me think it was all the way in. I took slack off of the derailleur cage by hand and while holding it in place was able to get the limit screws turned in more which set the low limit where I wanted it. Its not completely dialed in, but I feel as though I can now follow all of the advice here and other tutorials I've read to get it where others to be.

    Thanks for all of the help.

    Sent from my LG-H820 using Tapatalk

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