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  1. #1
    Desert Rat
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    Old MTB/Crankset ?

    I have an old GT Timberline with a 7 speed cassette on it. The chainrings are still the original bio pace shimanos and they are worn out or soon will be.

    I am wondering if I get this crankset will it work with the 7 speed chain and cassette? Will it work with the current shifters I have? What would I need to change to make it compatible? Remember that I don't want to buy a completely new drive train if I can avoid it.

    The ideal scenario is to just install the crankset and bottom bracket. What issues would I run into if I just do that? If I have to change to an 8 or 9 speed cassette will I have to replace the rear hub as well?

    Currently I have all shimano components except the cassette which is shimano compatible. I'm pretty sure the derailers will work unless there is an issue with the index spacing. The shifters are shimano revoshift (twist grip).

    Thanks in advance for the help.
    Have I mentioned that I love riding my bikes?
    GT Timberline (1989), Home build (2012), Giant OCR3 (2007)

    Jack aka:makeitso

  2. #2
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    The only potential problems I can think of is that the chainline may not be perfect and that this one may be the wrong size. Some MTB's were built with 73mm bottom bracket shells and I don't think that a 68mm bottom bracket will work.

    You can measure the shell pretty easily. You want to measure the length of the pipe, basically, not the diameter. If it's 73mm, you'll need a 73mm bottom bracket.

    The external bearing bottom brackets are more sensitive to alignment as well, so you may need to take the frame in and get the BB shell faced before you install the new one.

    Alternatively, you can purchase and install new chainrings for a pretty reasonable price. You could look into this at aebike.com or biketoolsetc.com. You would be best with chainrings that are ramped and pinned.
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  3. #3
    Senior Member TimJ's Avatar
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    Quote Originally Posted by Makeitso View Post
    I have an old GT Timberline with a 7 speed cassette on it. The chainrings are still the original bio pace shimanos and they are worn out or soon will be.

    I am wondering if I get this crankset will it work with the 7 speed chain and cassette? Will it work with the current shifters I have? What would I need to change to make it compatible? Remember that I don't want to buy a completely new drive train if I can avoid it.

    The ideal scenario is to just install the crankset and bottom bracket. What issues would I run into if I just do that? If I have to change to an 8 or 9 speed cassette will I have to replace the rear hub as well?

    Currently I have all shimano components except the cassette which is shimano compatible. I'm pretty sure the derailers will work unless there is an issue with the index spacing. The shifters are shimano revoshift (twist grip).

    Thanks in advance for the help.

    You could just buy new chainrings. You could also get a decent crankset for a lot cheaper. I found a new deore hollowtech crankset w/ octalink bb on ebay for $50, and it's a nice piece of gear.

    Anyway, your 7 speed hub won't be able to take an 8 or 9 speed cassette. If you got a 9 speed crankset you could use it w/ your 7 speed rear, I'm not sure but you may want to use a "9 speed" chain. 7 and 8 are the same width (chains), 9 is slightly narrower, but the only reason a 7/8 speed chain would be a problem on a "9 speed" crankset is if the rings were a bit closer together so you'd get rubbing easier, but I don't know if the rings are closer together, so...

    Basically no, you don't have to replace the whole drivetrain. You can get whatever cranket you want, if it's "9 speed" crankset there's a chance you will want to get a 9 speed chain.

    Oh yeah- I seriously doubt your bb is anything but 68mm.
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  4. #4
    Desert Rat
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    The BB is 68mm for sure. I just put a new one in about 6 months ago.

    This bike has the bio-pace shimano rings on it. Can I use something else or do I have to find them? I was told I could not replace those with anything but bio-pace rings.
    Have I mentioned that I love riding my bikes?
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  5. #5
    Senior Member Bill Kapaun's Avatar
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    What are the current tooth counts on your rings?
    Looking at bikeapedia.com, the range of ring sizes for your brand and model ran from 28-38-48 to 22-32-42 for the 3 I checked.
    http://www.bikepedia.com/QuickBike/B...line&Type=bike

    You might possibly have clearance issues if say, your bike is equipped with a 42T big ring. Better to check that out first. You might also have FDER issues if you have no vertical adjustment on the FDER.

    Personally, if the BB is good, I'd just look for a lower cost sq. taper crank set. Youur bike has relatively lower end parts and it just seems like too much money for what you want to do.
    IF you want a cheap 28-38-48 sq, taper crank with SHORT arms, see-
    http://www.nashbar.com/profile.cfm?c...20ATB%20Cranks

  6. #6
    Desert Rat
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    It has the 28-38-48 on it right now. I don't want the cheapo riveted crankset from nashbar. It has too short of arms on it. My current ones are 175mm.
    Have I mentioned that I love riding my bikes?
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  7. #7
    Senior Member TimJ's Avatar
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    Quote Originally Posted by Makeitso View Post
    The BB is 68mm for sure. I just put a new one in about 6 months ago.

    This bike has the bio-pace shimano rings on it. Can I use something else or do I have to find them? I was told I could not replace those with anything but bio-pace rings.
    No, you can replace the rings with whatever you want. Biopace only had to do with the shape of the rings, there was nothing different about the crankarms. Chainrings can be pretty pricey though. For instance:

    http://www.jensonusa.com/store/produ...nring+Set.aspx
    fun facts: Psychopaths have trouble understanding abstract concepts.
    "Incompetent individuals, compared with their more competent peers, will dramatically overestimate their ability and performance relative to objective criteria."

  8. #8
    Desert Rat
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    Quote Originally Posted by TimJ View Post
    No, you can replace the rings with whatever you want. Biopace only had to do with the shape of the rings, there was nothing different about the crankarms. Chainrings can be pretty pricey though. For instance:

    http://www.jensonusa.com/store/produ...nring+Set.aspx
    That's why I thought I would just replace the whole Crankset with the one at the link in the original post.

    I have some great feed back here but no one has answered my question with certainty. Given the information contained in this thread will this crankset and BB work with what I have on the bike right now?

    I have a 7 speed cassette.
    The current BB is 68mm.
    The current rings are 28-38-48.
    I am keeping the bike either way so I want something that will last.

    The main questions are these:
    If I put this crankset on my bike do I need to change the chain, cassette, both or neither?
    Can I install this crankset/BB and ride off into the sunrise?
    Will the indexing on the front shifter match the spacing on the chainrings?

    As far as I know:
    7 speed chains are the same as 8, 9 or 10 speed chains except the side plates are narrower and the rivets are shorter.
    The cassettes on an 8, 9 or 10 speeds have less space between the individual sprokets but are the same tthickness.
    I don't know about the indexing (this is only a concern for the front shifter).
    Last edited by Makeitso; 09-02-08 at 06:57 PM.
    Have I mentioned that I love riding my bikes?
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  9. #9
    Senior Member BCRider's Avatar
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    Yes that one will work and it'll work wiht the correct chain line since you're replacing all the stuff.

    That's pretty pricey considering it's the "old" Octalink stuff and the external cup setups are all the rage now. I've seen some places selling the old Octalink stuff for just over 1/2 the price BikeUSA wants.

    Shop around some more. Hell, Jenson's has an FSA Mega EXO external bearing crank and BB setup for $90. That's a major upgrade and a nicer setup for $40 less than the one in the link. And that's all just from one quick check.

    Look at Jensons, Nashbar, Performance and Cambria. There's others as well. You can find links to them either with Google or in the listing of online shops at www.mtbr.com .

    Don't worry about using 7 speed chain on 9 speed rings. It'll work just fine. The only other issue is that most all modern MTB cranksets use big rings that are 44 while yours is 46. Unless you often speed along on the 11 on the rear, big ring on the front and find yourself wishing for more it won't be a problem.
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  10. #10
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by BCRider View Post
    Yes that one will work and it'll work wiht the correct chain line since you're replacing all the stuff.

    That's pretty pricey considering it's the "old" Octalink stuff and the external cup setups are all the rage now. I've seen some places selling the old Octalink stuff for just over 1/2 the price BikeUSA wants.

    Shop around some more. Hell, Jenson's has an FSA Mega EXO external bearing crank and BB setup for $90. That's a major upgrade and a nicer setup for $40 less than the one in the link. And that's all just from one quick check.

    Look at Jensons, Nashbar, Performance and Cambria. There's others as well. You can find links to them either with Google or in the listing of online shops at www.mtbr.com .

    Don't worry about using 7 speed chain on 9 speed rings. It'll work just fine. The only other issue is that most all modern MTB cranksets use big rings that are 44 while yours is 46. Unless you often speed along on the 11 on the rear, big ring on the front and find yourself wishing for more it won't be a problem.
    That crank is a Hollowtech II which is external bearing. However the price is somewhat high for Deore. Check around for an LX (although most of those are going to be 44/32/22 and not 48/36/26). I've seen them at about the same price.
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  11. #11
    Desert Rat
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    Cool, thanks. I will do some shopping around. I just need to know it works. I'm not in a hurry to get this exact one.

    Thanks all for the input.
    Have I mentioned that I love riding my bikes?
    GT Timberline (1989), Home build (2012), Giant OCR3 (2007)

    Jack aka:makeitso

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