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  1. #1
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    New question here. HELP: no "B-tension" screw on Shimano Tourney rear derailluer (RD-FT30) ?

    Hi folks,

    So I recently picked up an used '09/'10 Hotrock for my daughter, and it has a Shimano Tourney rear derailluer (RD-FT30).

    When in the lightest/largest cassette cog, the upper pulley hits it, being too close to each other. So, I thought to adjust the B-tension screw as usual, only to find that there's no such on this rear derailluer. (There're only the usual high- and low-range adjuster screws.)

    So, without the B-tension screw, how do I make this adjustment with this rear derailluer?

    Shimano tech docs: Tourney

    Thanks for your info in advance,
    - PiroChu
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  2. #2
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    Based on that tech-doc the b-tension screw is in the body of the derailleur right by the cable adjuster barrel. Part #4 on those diagrams.
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  3. #3
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    Quote Originally Posted by Shayne View Post
    Part #4 on those diagrams.
    Sorry, my bad, I should've specified (just edited/specified in my original title/post now.)

    It's RD-FT30 of the Tourney line, and that model doesn't have the "part#4" (B-tension); hence my question.

    http://techdocs.shimano.com/media/te...9830607125.pdf
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  4. #4
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    Quote Originally Posted by PiroChu View Post
    Sorry, my bad, I should've specified (just edited/specified in my original title/post now.)

    It's RD-FT30 of the Tourney line, and that model doesn't have the "part#4" (B-tension); hence my question.

    http://techdocs.shimano.com/media/te...9830607125.pdf
    I chose to upgrade that derailleur for this for 16 bucks problem solved
    Shimano Tourney TX55 6 7 Speed Rear Derailleur Direct Attach | eBay
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  5. #5
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    Figured it out...

    So, the B-tension for RD-FT30 is simply "adjusted" by the length of the last piece of cable housing ("X + 10mm" per PDF manual), LOL.

    It was too long before. Anyway, upon re-adjustment, it works fine now, thanks.


    {EDIT}
    And here's a pic (taken on 7/11/'13)...
    HELP: no "B-tension" screw on Shimano Tourney rear derailluer (RD-FT30) ?-img_1318.jpg
    Last edited by PiroChu; 07-16-2013 at 01:07 PM. Reason: added a pic
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  6. #6
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    Huh? I admit there's a ton I don't know about bikes, but how does the length of housing change anything? I can see how the cable tension (relative length of cable housing to the cable) might change things, but you can adjust that by loosening the set screw and tightening or loosening the inner cable.

    Can someone tell me what I'm missing here?

  7. #7
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    Quote Originally Posted by evandy View Post
    I can see how the cable tension ... might change things
    Basically, think of "B-tension" as an "angle" (rather than "tension") adjustment.

    I'm not the best to explain this, so here's a quote from Sheldon's...
    Most derailers have an angle adjustment screw (Shimano calls it "B-tension adjustment"). This adjusts the tension of the upper ("b") spring of the parallelogram, and thus the height of the jockey pulley. The looser this screw is, the closer the jockey pulley will be to the cluster.
    Derailer Adjustment by Sheldon Brown
    Park Tool Co. ParkTool Blog Rear Derailler Adjustments (derailleur)

    So, normally the screw holds the derailluer angle, which is not affected by the length of the last piece of cable housing. (eg. If too long, it'll just flare out, while the screw still keeps in the same angle.) However, in the case of this cheapo rear derailluer, there's no screw to hold it to an set angle, so the length of the last-segment housing has to (sorta) "functionally act" as such.

    Again, probably not best describing it, but anyways it works now.
    - PiroChu
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  8. #8
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    Ok. That's weird and worrysome, but makes some sense at least.

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    Quote Originally Posted by PiroChu View Post
    Figured it out...

    So, the B-tension for RD-FT30 is simply "adjusted" by the length of the last piece of cable housing ("X + 10mm" per PDF manual), LOL.

    It was too long before. Anyway, upon re-adjustment, it works fine now, thanks.
    I've got exactly the same issue with the B-tension on a Shimano Tourney so I'm really pleased to have found such a recent thread on it. Can you explain how to measure the length of cable housing required, or point me in the direction of a manual?

    Would I be right in thinking that the cable housing needs to be shortened?

    Thanks

  10. #10
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    Quote Originally Posted by Tobyedward View Post
    Can you explain how to measure the length of cable housing required, or point me in the direction of a manual? Would I be right in thinking that the cable housing needs to be shortened?
    The Shimano online PDF manual (links in above posts) says the following:

    Cable securing and stroke adjustment
    If routing the casing upward:
    Add 10 mm to the length of the outer casing
    from the end that is inserted into the outer
    casing holder to the end which is inserted into
    the link.
    If routing the casing downward:
    Set the length of the outer casing so that it describes a smooth arc
    So, the measuring method is slightly different, depending on whether your rearl-derailluer cable runs along the seatstay ("upward") or the chainstay ("downward").

    My daughter's '09 Hotrock runs it along the seatstay, so I followed the "(distance) + 10mm" formula, and now it works fine. The original piece was too long, and I had to cut it down by about an inch or so. (I actually kept a tad extra, about "distance + 15mm-ish".)

    To measure this "distance" portion of the "(distance) + 10mm" formula with the seatstay route, make sure to note the 'angle/position' of the rear-derailluer when it's in the largest cassette cog, then measure it from the last cable stop on the frame to the first cable entrance on rear derailleur.)


    Regardless of whichever cable routing, if the last piece of cable housing is too long, the upper pulley will hit the largest cassette cog. If too short, I'd imagine that they'll be too far apart (also not desirable). They say that the "width-of-a-pencil apart" cog-to-pulley is appropriate.

    Good luck,
    - PiroChu
    Last edited by PiroChu; 07-12-2013 at 10:21 AM.
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  11. #11
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    Thanks PiroChu - that's really helpful. Mine runs along the chainstay so I'll go for the smooth arc as described, but as the housing is currently too long, I'll probably cut it down gradually and test as I go to avoid going too short.

    Thanks again.

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