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  1. #1
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    1992 Trek 950 front derail-bottom pull???

    I have decided to keep this 15" Trek 950,and sell my 1993 Trek 930 (13") despite the 13" having a 3/4' lower standover.I just like the lugged frame with monotone paint more than the blended 2 tone 930 with triple butted OX II tubing(vs double butted OXII on the 950).
    The front derailleur that came with it sure seems to pull from the bottom.It matches the rea LX Deore derailleur just fine, but I don't see anywhere to screw attach a cable guide, and I don't see a print from a clamp on cable guide.
    My question.
    1)Was it the original derailleur? Doesn't seem it could be??
    2)If original how does it work-am I missing something?
    The guy I got it from was just going to bring it back in service,so he might very well have found a matching looking ft derail,and didn't notice the bottom pull problem.No stones at him-he didn't make any originality claims,and I don't give a "heck" about originality on a bike like this anyway.I bought it to play with/fix,and sell to a local student for maybe $180 or so.
    Thanks,
    Charlie
    PS I used this -CV)rather than MTB forum, because there are more older folks here,and it is "that"sort of question.I was out of biking from 1982-2000-so I missed these originally.
    The first picture-not good-is the bottom of the BB-it is supposed to show no screw holes.By the way,what is the boss with the 8 mm head screw in it??I have no idea?
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    Last edited by phoebeisis; 12-28-07 at 12:32 PM.

  2. #2
    Lanky Lass East Hill's Avatar
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    No experts out there who want to venture a guess?

    East Hill
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  3. #3
    juneeaa memba!
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    The banjo mounts on the top tube...there are three slots, right? If there are three places, the bike was intended for a top pull front derailleur. I don't recall for sure(someone else will) but I think that the way that this front derailleur was intended to work was by running a piece of cable housing from the rear set of cable stops on the top tube to the cable stop on the derailleur. you can sort of see the arrangement in this picture from first flight bikes (the derailleur is the same as yours, I think).
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  4. #4
    Senior Member Lamplight's Avatar
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    Some mountain bikes with top-tube cable routing still used bottom-pull front derailleurs. They did this by mounting a little wheel, usually plastic, below the derailleur on the seat tube. The cable routed down through the wheel and back up to the derailleur. It's hard to tell with the kickstand in the way, but that little boss you're seeing may be a wheel mount. However, it looks like it would be too low and not have nearly enough clearance for a wheel with the chainstays so close. Perhaps it had some other sort of adapter that mounted there. Your best bet is to either try to make an adaptor yourself, or just buy a new derailleur. That's a great bike, by the way.

  5. #5
    Senior Member raverson's Avatar
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    My Fuji Folder commuter/travel bike came with top tube cable routing and a bottom pull FD. As Lamplight mentioned, they routed the cable through a wheel mounted to a M5 boss on the back side of the seat tube, in this case positioned halfway between the FD clamp and the BB. A long way around the barn solution.

    When I upgraded the bike to modern Deore, I used a top pull, top swing LX FD. The clamp lined up directly over the wheel boss, so I ground it off with the dremel.
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    Last edited by raverson; 12-29-07 at 11:46 AM.

  6. #6
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    looks like a bottom pull to me

    yes it does like a bottom pull to me. you could get an adapter if there is a screw hole in the shell to run the cable underneath. if not you would need drill and tap some threads.

    you could also try to fund some onl shimano or suntour screw on cable stops to run on the down tube. if you have oversized tubing you probably wont find anything compatible.

    other than that **** can the der and hit a used shop and pick up a top pull if the frame is set to bring the cable down from above

  7. #7
    Senior Member balto charlie's Avatar
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    I just scored a late 80's early 90's Trek 990. It is mostly original(different wheels). It has 3 cables running along the top tube, with the FD being a top pull with XT non-indexed thumb shifter. The RD is indexed. I can't tell you more then this because the bike is at work. I'll let you know more next week. If I forget please email me and I'll get more info to you. Charlie(another one)

  8. #8
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    EastHill,Luker,Lamplight,Raverson
    Thanks for the help.Normally,I would have assumed the PO had just put on a derailleur that matched the RD , but hadn't gotten around to finding out it wouldn't work-just the usual bump in the road you get doing projects with a mix and match parts box(room).
    However,this one matches the rear derail in all respects-model/age/wear-and it matches the shifters.
    Shimano DEORE LX with the shiny black finish.
    Here is a much better picture of the boss.I took the side stand off.
    Raverson-yes the screw is 5mm(.193"-cheap caliper) with a 8mm head.
    Lamplight-I have substituted a top pull top swing 34.9 XTR derailleur,and shmmed it with a shim dohickey kit off an LX derailleur(31.8 clamp on the original derail-)I think it will work, but I never can be 100% sure until the cable is hooked up and it is working.I've tried so many things that "should work".
    Luker-yes there are three slots on the top tube-just as you would expect with a top pull derailleur.
    Thanks,
    Charlie
    PS-The old derailleur is fairly light-134 grams-less than current LX.The XTR is 109+7(shims)=116 grams
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  9. #9
    Senior Member Lamplight's Avatar
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    Quote Originally Posted by luker View Post
    The banjo mounts on the top tube...there are three slots, right? If there are three places, the bike was intended for a top pull front derailleur. I don't recall for sure(someone else will) but I think that the way that this front derailleur was intended to work was by running a piece of cable housing from the rear set of cable stops on the top tube to the cable stop on the derailleur. you can sort of see the arrangement in this picture from first flight bikes (the derailleur is the same as yours, I think).
    If the bike doesn't have another cable stop somewhere on the seat tube, then I bet luker's idea is the most likely to be correct. The boss on the bottom bracket shell may have been for some sort of cable stop which redirected the cable back up toward the derailleur. If you don't find another cable stop on the seat tube, then you may have to find an adapter like that.

  10. #10
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    Lamplight,
    Nope, no cable stops. Now,there is a hanger on the seat post that I might end up using for either the derailleur or the rear brakes.It is currently cantilever brakes, but I'll switch to V-brakes,so it won't need that hanger for the brakes.
    My Trek 930-which I think is one year later-no lugs-triple butted OX II has a brazed stop on the seat tube,and it has a fancy little brake hanger on the seat stay cross member. The fancy gadget is sprung,and adjustable. My Trek 950 has a hole in the cross member for it-and flats on the cross member to install one-but no sign-marring-that one was ever installed.The pictures-930 fancy gadget-950 no gadget-lie a little.The 950 surface looks slightly marred, but that is strictly my poor photo.
    I'm thinking about using the hole in the cross member as a cable stop for the derailleur.I would have to slightly "plug" un underside,so the cable would actually stop.
    Thanks,
    Charlie
    PS I think you guys are right.The bottom pull derailleur was original,and that boss with the screw in it had some sort of wheel to reverse direction of the cable.The seat tube hanger on the 950 must have been for the brakes.The original derailleur has a swivel cable stop on it,that I didn't really understand.
    It must have stopped the cable casing that came from above,allowed the cable thru it to go down to the wheel,and come back up to the cable fastening screw.The picture is showing the cable stop,and the cable fastening screw.Wow,that is certainly doing it the hard way.
    Thanks for the help.I absolutely could have never figured this out with help.I'll hunt for a reversing wheel, but I don't expect to find one.I'll see if I can find a clamp on cable stop for the seat tube.Hanging the derail cable from the brake stop cross member hole isn't very elegant, but it will do for now.
    Charlie
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  11. #11
    juneeaa memba!
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    lemme try again. The cable housing runs from the top tube stop to the cable housing stop on the derailleur. The cable passes through and is fixed to the bolt at the bottom. The derailleur is made to work by the housing pushing on the cable stop that is on the derailleur; the cable (in this setup) just provides the equal and opposite force to make the housing do the work. If you could find some other way to secure the cable housing that is needed to route the cable down...and a pulley that works with the bolt and boss at the bottom...then you could use a conventional bottom pull derailleur.

  12. #12
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    Luker,
    Yes,that is it.One peculiar aspect is that the stretch of housing from the top tube stop down to the cable stop on the derailleur is going to move downward as the arm is pulled from below.I will have to have about 3/8" of bow in that stretch of housing/cable.No problem (I think, but I will have to see it in action to be 100% sure), but kinda' odd.
    This seems incredibly complicated, but this is how they did it.No other good explanation.I think having the stop way down on the derailleur instead of on the seat tube-MIGHT-give the cable a more gently turn/angle,and a smoother action.We'll see.
    Thanks all.
    Charlie

  13. #13
    juneeaa memba!
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    what is the model number on that derailleur?

  14. #14
    Senior Member Lamplight's Avatar
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    Now that I see the picture of the original derailleur up close, I can see how it works. Very unusual, but at least you can make it work. BTW, that little V-shaped device for the brakes can work very well when adjusted carefully. V-brakes are still better though.

  15. #15
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    Luker,
    It is a Shimano M-550.
    Lamplighter-yes,the little V-shaped springloaded brake "thing" works fine, but it is one more twitchy adjustment on the cantilevers which are harder to adjust than the V-brakes.The Cantilevers seem to stop just as strongly as V brakes, but they sure take more initial fiddling.
    Thanks,
    Charlie

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