X-post: Chainline Issue?- Mtbr.com
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  1. #1
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    New question here. X-post: Chainline Issue?

    Hello, Homers. Thougt I'd post over here as well to gather your collective wisdom as my bike is not shifting as well as I thought, so I thought I could improve it to get rid of the derailleur cage rub from the chain. It irritates me to no end. Thus far I've had no such luck after after an hour or so of fiddling with the barrel adjusters and rotating the FD.

    The parts list (I do not have a chain tensioner/guide anymore):
    1. Raceface Atlas cranks with X-type BB
    2. 73mm BB shell of a 2005 Six Pack/RFX
    3. 24/34/bash chainring set up
    4. Top pull/bottom swing Shimano XT front derailleur
    5. 11-32t 8-speed SRAM cassette
    6. SRAM 8 speed chain

    Initially I did not add any BB spacers to the driveside, but after looking at the directions from Raceface it said to add 2.5mm worth of BB spacers to the drive side, which I did. (I added non-raceface spacers as I lost the originals from raceface), but things have just been not quite right since then. Should I even bother following directions? To make matters worse, my LBS lost one of the spindle spacers too.

    Anyhow, just seeing if any other homers out there use the same cranks and how, where and how many BB spacers and spindle spacers they used to avoid chain rub on the derailleur. My goal is to have the drivetrain run silent when in the middle ring and any cog in the rear. Is this even possible?

    One of the responses I got from the other post was that maybe my ring choices could be an issue as there is only a 10 tooth difference between the middle and granny ring, but I doubt it. Most three chain bikes are 44/32/22, right? There's still only a 10 tooth difference in that set-up as well.

    One last thing, could anyone give me a basic lesson about chainline? I've got sort of a basic, nebulous idea, but don't know happens to chainline if I add spacers here or there.

    Thanks!

  2. #2
    No, that's not phonetic
    Reputation: tscheezy's Avatar
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    Quote Originally Posted by oreo
    My goal is to have the drivetrain run silent when in the middle ring and any cog in the rear. Is this even possible?
    No, this is quite simply not possible. Had you read the sheet which came with the front der you would know this. We all read ALL the directions, right? You can either trim the der not to rub in the low gears, or in the high gears, but NOT BOTH. Thanks Shimano...

    Anyway, switching to a grip shift up front would allow you to trim the der. An iPod works well too. Or hold your thumb on the paddle for those rare instance when you are in the 11t. I can get my front der to not rub in all but like one cog in the back. I can live with that.

    Aside from that, I recommend putting all the spacers on the non-drive side. I prefer narrower chain spacing personally.
    My video techniques can be found in this thread.

  3. #3
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    Quote Originally Posted by tscheezy
    Aside from that, I recommend putting all the spacers on the non-drive side. I prefer narrower chain spacing personally.
    Out of curiousity, why do you prefer the narrow chain spacing?

  4. #4
    No, that's not phonetic
    Reputation: tscheezy's Avatar
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    I spend more time in the "lower" end of the cassette (larger cogs) and am exerting more long-term chain torque in those gears (climbing as opposed to spinning on the flats). There is less cross chaining that way when it matters. Also, the chain does not "drop" onto larger cogs when you are bouncing around, only smaller ones. Cuts down on that too.
    My video techniques can be found in this thread.

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