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Rear derailleur questions

Started by sfcycle · · Last activity · 7 posts · 676 views

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01 / Original postRear derailleur questionssfcycle · 3 Aug 2007 02 / This pagePosts 1–7Page 1 of 1 · chronological order 03 / Latest replyPost #7pistole · 3 Aug 2007

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Original section
Cycling Equipment
Published
3 August 2007
Last activity
3 August 2007
Original author
sfcycle
Posts
7
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Public discussion
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676
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0
Topics
Rear derailleursDrivetrain compatibilityGiant

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  1. Original post
    sfcycle
    Archived post
    #1

    Hi all,

    New to the board and new to fixing my own bike.

    I've got a 1997 Giant mountain bike that came with a Shimano 7 speed derailleur. The derailleur is bent and I want to replace it and somewhat upgrade the component. (Better component, but not crazy $$ component)

    As I look around at derailleurs, I see some 8 speed and a lot of 9 / 10 speed.

    It appears that the 8 speed could be used for a 7 speed, but how about a 9 speed? Is it a matter of limiting the derailleur travel to go through 7 gears instead of 9 or are there inherent differences that would make that not possible. Sorry for the basic questions, but trying to learn.

    Given the above, any recommendations on a quality, yet not grossly expensive derailleur for my 7 speed? I'll throw out $40 - $50 as a price range I consider reasonable for me.

    Thanks for any info you can offer.
    Mike

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  2. gclark8
    Archived post
    #2

    Mike, is the Derailleur frame mounted or axle mounted?

    Shimano have both and the quality is excellent, flow down from the higher level components. ... Look for:

    Quoted post said:

    RD-TX50 REAR DERAILLEUR 6/7-SPEED AXLE MOUNT
    RD-TX50 REAR DERAILLEUR 6/7-SPEED FRAME-MOUNT

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  3. John M
    Archived post
    #3

    9/10 will have too narrow of a cage for your chain. You could use a 9-s with a 9-s chain in your drivetrain, but to no advantage (and a front shifting diminished performance).

    If you can't find a suitable 7s, an 8s will work well.

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  4. Retro Grouch
    Archived post
    #4

    Not to worry.

    Rear derailleurs don't care about how many cogs you have on the back. They guide the chain from the center and all chains are the same width in the center.

    Rear derailleurs do have some differences in how they mount on the bike frame so you need to match what you have. There are also some differences in matching your shifters so, on a 1997 bike, you need to take that into account.

    Honestly, without seeing your derailleur, I'm not convinced you need to replace it. Generally, on a 7-speed bike, you should be able to "eyeball" your derailleur back into line accurately enough to repair your shifting.

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  5. sfcycle
    Archived post
    #5

    Thanks for the comments so far.

    The derailleur is frame mounted, just below the axle.

    The derailleur does shift generally ok. What made me wonder about replacing it is when I look down as I'm riding, the chain on the top and bottom are not in alignment and I am under the impression they should be in line to avoid side pressure on the cogs, almost like cross chaining (if my lingo is right). It appear the derailleur is bent inwards.

    From your comments it sounds as if I could "gently" coax the derailleur back in line...???

    I was thinking about nursing the old along and then replacing it this winter, but we'll see how the realignment goes.

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  6. gclark8
    Archived post
    #6

    "RD-TX50 REAR DERAILLEUR 6/7-SPEED FRAME-MOUNT"

    It should be no more than $20 and will be compatible with the existing chain and cassette profile. They are cheap enough to replace if you doubt the reliability of the one you currently have on the bike.

    The Frame Mounting RD-TX70 and RD-TX 30 will also be suitable.
    http://www.shimano.com.au/catalog/cycle/products/group.jsp?FOLDER%3C%3Efolder_id=2534374302037283&ASSORTMENT%3C%3East_id=1408474395181400&bmUID=1186178742185

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  7. pistole
    Archived post
    #7

    - just bend the thing back into line.
    .

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