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  1. #1
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    Installing a rear derailleur tomorrow for first time...

    Hey all,

    I bought a used Trek 3700 mountain bike, and the very next day started having weird issues. Anyway, I am pretty sure that the derailleur hanger was bent, so I picked up a new one of those. The guy at the bike shop wasn't 100% sure that it was an exact match to the original, however. It looks pretty darn close. Do you think this will be an issue? Also, I am not going to have a front derailleur, for the time being, because at the moment I don't have the time/money to pick one up and install it.

    So if the hanger isn't an exact match to what came with the bike, will this be an issue? Also, will not having a front derailleur effect the back derailleur? I plan on not really shifting at all, until I get a front dee. I just need something to take up the slack in my chain (my chain tensioner also isn't working... I'm having all sorts of issues.)

    Thanks.

  2. #2
    Senior Member Miyata110's Avatar
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    It's hard to say without specifics, but you'll probably be okay. Post what the 2 RDs are and I'm sure someone will be able to say definitely.

    I can't see how the lack of a FD would affect anything (other than the obvious).

  3. #3
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    I would keep the bike in the middle cog on the front and you should be able to shift though all the gears in the rear.

  4. #4
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    Quote Originally Posted by bobotech View Post
    I would keep the bike in the middle cog on the front and you should be able to shift though all the gears in the rear.
    noted. Thank all

  5. #5
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    Quote Originally Posted by Miyata110 View Post
    It's hard to say without specifics, but you'll probably be okay. Post what the 2 RDs are and I'm sure someone will be able to say definitely.

    I can't see how the lack of a FD would affect anything (other than the obvious).

    I have the original RD, but not exactly sure what model # it is, etc. (it may say on the RD itself). And I know what Im buying is this;

    Shimano (don't know model, but either altus, acera, or alivio) 8 Speed Shifter - $10
    Shimano Altus 8 speed derailleur - $15

    Hopefully I'll get some info on these RD's compatibility. Thanks

  6. #6
    Senior Member Bill Kapaun's Avatar
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    Quote Originally Posted by FreakyFast View Post
    ......Shimano (don't know model, but either altus, acera, or alivio) 8 Speed Shifter - $10 Shimano Altus 8 speed derailleur - $15

    Hopefully I'll get some info on these RD's compatibility. Thanks
    These are all "mountain" components and compatible with each other.

  7. #7
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    FF, As long as the hanger's mounting holes match the dropout and the slot for the axle isn't blocked in some way, you should be good.

    As far as installation goes, there is a screw at the very rear of the RD. Make sure it clears the dropout before tightening the mounting bolt as it's designed to contact the rear of the hanger.

    Be sure to buy a FD from a mountain group when the time comes.

    Brad

  8. #8
    coprolite fietsbob's Avatar
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    Instruction sheets are commonly inside the box a new derailleur is shipped in.

  9. #9
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    Went to my LBS after giving up: I am not mechanically inclined. I managed to get the derailleur screwed on and run the cable (I had to use old cable housing cause I didn't buy enough, and cutting it without proper tools is a pain). My cassette was 7 speed, and the shifter was 8 speed, so I had some issues. I learned that I need to give up altogether on bike maintainence, or just have the right tools and supplies (like cable cutters and a bike stand) before attempting anything in the future.

  10. #10
    Senior Member Bill Kapaun's Avatar
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    You just MIGHT have stumbled on some good fortune!
    Many of the better 7 speed bikes actually use an 8/9 speed Free Hub body with a 7 speed cassette.
    In this case, there would be a 4.5MM? spacer that goes on the FH body before the cassette slides on.

    IF that's the case, all you need is a low cost 8 speed cassette and voila- You have an 8 speed.
    For example-
    http://www.loosescrews.com/index.cgi...d=904428827650

    You remove this-
    http://www.loosescrews.com/index.cgi...d=904428827650
    Last edited by Bill Kapaun; 02-15-12 at 10:42 PM.

  11. #11
    Senior Member LesterOfPuppets's Avatar
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    I've always been better off running the big ring sans FD, unless I shortened chain some. Even then I'd lose chain sometimes. Ideally get a FD or a singlespeed chainring - bigger teeth = less droppage!

    To dial in a 7sp cogset with 8sp shifter you have to pick which cog you don't want, set limit screws accordingly and just have an extra click. It often works OK
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Lemond Buenos Aires Triple

  12. #12
    Senior Member Bill Kapaun's Avatar
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    You can't "dial in" 8 speed shifters with a 7 speed cassette or vice versa.
    The spacing between cogs is .2MM different. 6 shifts and you are 1.2MM different or about 1/4 of 1 cog spacing.
    Just because you might be able to get it into all the gears, who wants to put up with the noise & chain rub?

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