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  1. #1
    Senior Member BezO's Avatar
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    Replacing Crankset - Questions

    Trying to read up on this confused me more than it helped.

    If I want to use my current bottom bracket, what should I be concerned with regarding the new crankset?
    My BB is 68x103 tapered square. Not sure it's relevant, but my current chainring is 46T with a 130 BCD(according to this chart).

    Is it better to change the BB along with the crankset to be sure everything is compatible?

    Either way, since my freewheel is involved in creating the chainline, are there measurements back there I need to be concerned with?

    Because I want a chain guard, and they seem non-existant for 46/48T chainrings, I'm considering the Sugino XD2 w/guard. There's no BB compatibility info listed and I'm not sure what to ask.

    Any info would be appreciated.

  2. #2
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    Oh yay I get apply what i've learned.
    Step 1: Pick Crankset
    Step 2. find bb that fits cranks

    If you want to re-use your bb then find a crankset that is compatible with a 103mm and Square Taper spindle. Like this one : Click me baby!

  3. #3
    Senior Member BezO's Avatar
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    Thanks for the quick reply!

    So it's the length of the BB that's important? I'm guessing because of the chainline.

    That RD2 has the chain/tooth size & crank length I'm looking for. I just wonder why chain guards don't come in larger sizes? It's really the only reason I was looking at the XD2 that comes with the guard. But they don't list the BB length.

    I'm also realizing that I was mistaking the XD2 for the RD2.

  4. #4
    Senior Member Bat56's Avatar
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    These guys say the chainline with a 103mm is 45mm.

    See this post where dude says 110mm gives 45mm. The rest of that thread seems to indicate that 110 is the outer ring. Which makes sense.

    I think it's all a load of crap and you are screwed!

    46T bashguard $26 shipped

  5. #5
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    Quote Originally Posted by BezO View Post
    Thanks for the quick reply!

    So it's the length of the BB that's important?...
    yes...if by length you mean the spindle length to work with a particular crankset & you know whether taper is jis or iso.
    Crandrew gave you good advice & you could do worse than take it. rd2 is fine as a ss crankset, i had my ring on the outside & had perfect 43mm chainline. while there are many other cranks that could work with your bb, do you really need/want to spend more time & effort looking thru them?

    get smart & stop worrying about a chain/bashguard...

  6. #6
    Senior Member Kayce's Avatar
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    Why do you want a chaingaurd?
    If You Meet The Buddha On The Road, Kill Him

  7. #7
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    cause its JDM.

    edit: wrong forum

  8. #8
    Senior Member BezO's Avatar
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    Quote Originally Posted by Bat56 View Post
    These guys say the chainline with a 103mm is 45mm.
    According to a Sheldon Brown article, my chainline is likely 42mm. Now that I know how to measure it, I'll do so.
    Quote Originally Posted by Bat56 View Post
    46T bashguard $26 shipped
    I came across this site at some point. No 46T in silver. And I'll likely be going with a 48T crankset and they don't carry that size guard at all.
    Quote Originally Posted by markaitch View Post
    yes...if by length you mean the spindle length to work with a particular crankset & you know whether taper is jis or iso.
    Not sure about JIS vs ISO. I'll have to look into that.

    Quote Originally Posted by markaitch View Post
    get smart & stop worrying about a chain/bashguard...
    Quote Originally Posted by Kayce View Post
    Why do you want a chaingaurd?
    I've ruined 2 pairs of pants so far. Not a terrible ratio as I commute to work almost every day, but I'd prefer not to ruin another pair of pants.

    Thanks folks

  9. #9
    Senior Member Bat56's Avatar
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    Bashguard won't save pants. For real.

  10. #10
    The Stark Fist of Reality Scrodzilla's Avatar
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    FWIW, the Sugino RD2/Messenger claims to have a chainline of 45mm when using the proper 103mm BB but the set on my lady's bike measures closer to 43mm.

    OP - roll up your damn pant leg like the rest of us.

  11. #11
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    Quote Originally Posted by Scrodzilla View Post
    OP - roll up your damn pant leg like the rest of us.
    +1
    Its what the cool kids do.

  12. #12
    Senior Member thewilson's Avatar
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    Quote Originally Posted by BezO View Post
    Not sure about JIS vs ISO. I'll have to look into that.
    Thanks folks
    I might get some hate for this, But I wouldn't worry about iso - jis TOO much. I'm running an iso crank on a jis bb and have yet to have a single problem. But yes, ideally you'd want to have an iso with iso and jis with jis.

  13. #13
    The Stark Fist of Reality Scrodzilla's Avatar
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    True, but

    Quote Originally Posted by Sheldon Brown
    If you install an ISO crank on a J.I.S. spindle, it will sit about 4.5 mm farther out than it would on an ISO spindle of the same length.

    Confersely, if you install a J.I.S. crank on an ISO spindle, it will wind up about 4.5 mm farther in than it would on a J.I.S spindle of the same length.

  14. #14
    Senior Member Bat56's Avatar
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    Quote Originally Posted by Scrodzilla View Post
    True, but
    Quote Originally Posted by Sheldon Brown
    If you install an ISO crank on a J.I.S. spindle, it will sit about 4.5 mm farther out than it would on an ISO spindle of the same length.

    Confersely, if you install a J.I.S. crank on an ISO spindle, it will wind up about 4.5 mm farther in than it would on a J.I.S spindle of the same length.
    Confersely?

    Anyhoo - I love this little diddy. After making the mistake a few times over the years I have a bucket of bottom brackets and a few cranks. I don't know if they are JIS, or ISO, or WTF. Plus, it does not matter because some of the cranks are used a bit compressed (the tapers). I just slap stuff together until it works.

    I know this does not work with new stuff. And I apologize for that. But when splitting hairs over 2 mm here or there I do not believe that even new matched parts are going to work out perfectly every time. (Notice - I said "every" time.)

    All that said, know the information above allows you to mix and match your parts and use that too-long or too-short bottom bracket that you got a great deal on.

  15. #15
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    Chainguards are useless, unless they enclose the whole drivetrain. False sense of security. You will still suck your pants leg into it, just a little less often.
    Quote Originally Posted by Santaria View Post
    because physics has more street cred than tarckstars.

  16. #16
    Brown Bear, Sqrl Hunter Jaytron's Avatar
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    You can also get the sweet reflective bands that hold your pants tighter to your leg.

    Or just wear skinnier jeans.

    Or just roll your pant leg up.


    lol'd at replacing a crankset to solve the problem
    PedalRoom

    Hey I just met you,
    and this is crazy,
    but here's my Strava,
    follow me maybe.

  17. #17
    Senior Member BezO's Avatar
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    Quote Originally Posted by Scrodzilla View Post
    OP - roll up your damn pant leg like the rest of us.
    C'mon man. It's the 1 time out of 100 that I forget that's the problem.

    Quote Originally Posted by Jaytron View Post
    lol'd at replacing a crankset to solve the problem
    Yeah, it is funnier if you assume I'm changing my crankset instead of rolling my pant leg up.

    Quote Originally Posted by ianjk View Post
    Chainguards are useless, unless they enclose the whole drivetrain. False sense of security. You will still suck your pants leg into it, just a little less often.
    I've never actually had my pants leg eaten by the chain/crank. What happened each time was that I forgot to tuck my pants in my sock, went to put my foot in the strap & brushed my pants on the chain. The cleaners was not able to remove the stain.



    Fellas, chain/bash guard or not, I'm changing my crankset. I purchased the bike used for the frame. Many of the parts were old and/or cheap. I've been replacing them as I go. The cranks are next in line.

    I've seen the RD2 suggested a few times. The price & quality fit in with the rest of my bike. I mistook the XD2 for the RD2 & thought I found a great solution to 2 problems.

    But again, I get it. It's much more fun to set up jokes. I'm happy for the few serious answers. Thank you!
    Last edited by BezO; 08-23-12 at 12:27 PM.

  18. #18
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    We are just having fun. Im sure after the one pair of $200 pants are ruined you will remember to roll

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