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  1. #1
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    Can I fit a road Chainset on an MTB BB?

    Hello all.....
    Quick question.
    Can I use a road chainset like a 105 on a mountain bike frame with a mountain bike BB?
    If not could I fit a road BB to a Mountainbike frame and fit the 105 chainset on that. (Old Orange C16R)

    I understand that I will need to use a road front mech for the new ring diameter, but can I still use the MTB shifter pod (3 spd)?

    Many thanks,
    Tom

  2. #2
    Senior Member sydney's Avatar
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    Quote Originally Posted by KinesisTom
    Hello all.....
    Quick question.
    Can I use a road chainset like a 105 on a mountain bike frame with a mountain bike BB?
    If not could I fit a road BB to a Mountainbike frame and fit the 105 chainset on that. (Old Orange C16R)

    I understand that I will need to use a road front mech for the new ring diameter, but can I still use the MTB shifter pod (3 spd)?

    Many thanks,
    Tom
    The mtb shifter may or may not work with the road FD. Chainline for MTB is different for road and mtb triples. Your only option for the 105 crank other than the road 109 and 118 spindles is the XTR BB. Bigger chainings may create a chainstay clearance problem.. Bottom line, given the differences in requirements between mtb and road, it may be made to work or may not work for cr@p.

  3. #3
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    If you set the limit screws on the front derailleur, in theory you'd be able to use the front shifter that you've already got. The adjustment will take some time to dial in I'd imagine, but if you're patient in setting everything up it should work relatively well. I'm in a similar situation with an old mountain frame that I'm doing a cross conversion on, but I'm just going to run a flat bar with a triple and appropriate shifters until winter when I may get more brave and try to get a double on it instead. Like sydney said, biggest problem could be chainring clearance with a double. You're basically gonna have to try it to see if it'll work for crap or not.

  4. #4
    Senior Member sydney's Avatar
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    Quote Originally Posted by ImprezaDrvr
    If you set the limit screws on the front derailleur, in theory you'd be able to use the front shifter that you've already got. The adjustment will take some time to dial in I'd imagine, but if you're patient in setting everything up it should work relatively well. I'm in a similar situation with an old mountain frame that I'm doing a cross conversion on, but I'm just going to run a flat bar with a triple and appropriate shifters until winter when I may get more brave and try to get a double on it instead. Like sydney said, biggest problem could be chainring clearance with a double. You're basically gonna have to try it to see if it'll work for crap or not.
    There is more to FD and shifters than limit screws, especially with a triple. Shimano has long said that the road and mountain front stuff does not mix. Sometimes the combinatuion of mtb shifter road FD works better than the other way around.

  5. #5
    Senior Member Brian's Avatar
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    The chain, or the cogs and chainrings? No reason the chain alone wouldn't work - plenty of MTB racers use a Dura Ace chain.

  6. #6
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    Doesn't Shimano make two different Octalink bottom bracket designs? IIRC, one is used with road and XTR cranks, the other with XT and below and they are not interchangable.

  7. #7
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    I got lucky - when I tried this it worked for me. I put a 105 crankset and FD on a hybrid that had originally been a MTB triple. Since I was friction shifting, no problemo.

  8. #8
    Senior Member sydney's Avatar
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    Quote Originally Posted by HillRider
    Doesn't Shimano make two different Octalink bottom bracket designs? IIRC, one is used with road and XTR cranks, the other with XT and below and they are not interchangable.
    ^^^...correcto kind of. For '05 the sora and tiagra square taper cranks switched to octalink v2 mtb type
    Last edited by sydney; 11-02-05 at 02:16 PM.

  9. #9
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    Thanks for all your replies guys... very efficient.
    All in all it seems like it could be possible then.
    I will pick up a double chainset and a road mech, keep my XT 8 spd Cassette and Sachs 8spd chain and use my old STX front STI shifter and just adjust the limit screws on the deraileur.
    The chainring/chainstay clearance is a bit of a worry but as the frame is a skinny tubed steel Orange C16R I am hoping that the stays will not be too wide apart.

    The bottom bracket is still a bit of a mystery..... XTR has changed a lot over the last couple of years with their new cups and spiddle designs etc so I might need to investigate further before forking out. My 'cheap' road conversion using parts lying around is rappidly starting cost a bit more, especially with all this talk of XTR!

    Thanks for your help so far!!!
    Tom

  10. #10
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    Quote Originally Posted by sydney
    There is more to FD and shifters than limit screws, especially with a triple. Shimano has long said that the road and mountain front stuff does not mix. Sometimes the combinatuion of mtb shifter road FD works better than the other way around.
    True, I oversimplified a bit. It may work and I'd try it and see what happens before buying a new FD. It's one of those questions that's best answered by giving it a shot. There are a lot of variables at work. Fortunately, FD's aren't that pricey so if it doesn't work it's not a huge deal to slap a new one on.

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