understanding and replacing Cranksets & Bottom Brackets

Discussion in 'Cycling Equipment' started by bikingmat81, Feb 6, 2007.

  1. bikingmat81

    bikingmat81 New Member

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    So, I'm thinking about up-grading my crankset, and while I know what I want, I'm not sure if I can. I currently ride a 02 Specialized Rockhopper with the following componets:

    CRANKSET : Specialized Forearm II Comp, with black arms
    CHAINRINGS : 44Ax32Sx22S, w/black 7075 alloy outer ring, Tru-Shift
    BOTTOM BRACKET : Shimano BB-UN-52, square taper, 68 x 110

    (straight from Specialized website, as it's all still stock).

    I'd like to up-grade to a Race Face Evolve XC, but don't know if they are compatible, or what I need to look for in a replacement BB.

    Anyone got any website suggestions that can teach me the basics, or any other threads within this forum??

    Thanks
     
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  2. Insaneclimber

    Insaneclimber New Member

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    Hello, Its not as hard as it all looks.You will need a new bb as the shimano aint compatable with raceface. The bb is a 68 x 110. 68mm bieing the width of the frame where the bb screws in. 110 is the width of the axel. The axel width effects the spaceing of your feet and the alignment of the chain, often refered to as chain line. 110 is a narrow setup and for mountain bikeing you might want to go wider to a 113 or 118, this will give you more control in the rough. The other thing you need to look at is the length of your cranks, most mtb riders go for a 175. if you have short legs you might consider a 170. Likewise if your realy tall a 180 might be better. Here is a link to sheldon browns parts selection help http://sheldonbrown.com/harris/parts.html
     
  3. hd reynolds

    hd reynolds New Member

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    The Raceface is ISIS. Ask your LBS for the BB spindle that comes with the crank and for a 68mm BB.
     
  4. Paulie-AU

    Paulie-AU New Member

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    Bahaahaahaahaaaaa.

    Get the best chainline you can for shifting reasons.

    Buy an ISIS BB to suit the cranks.
     
  5. bikingmat81

    bikingmat81 New Member

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    I don't exactly have a LBS that I can run down to at the moment. I was planning to buy online, and have installed next time I'm close to a bike shop. I've bought off of pricepoint.com before, and had no problems. I just want to be sure that if I buy the one I'm looking at http://www.pricepoint.com/detail/13970-100_RACEX5-3-Parts-56-Cranks/Bolts/Race-Face-Evolve-XC-X-Type-Crankset.htm I'll be ok.

    Also, I came across this "X-Type integrated bottom-bracket system - not compatible with ISIS or other bottom-brackets". What sort of additional "problems" will this create?
     
  6. hd reynolds

    hd reynolds New Member

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    From the link you supplied, the X type uses outboard bearings similar to Shimano XTR or FSA mega Exo. The raceface comes complete with its own BB and is compatible with 68mm shells.

    You wont go wrong with this one coz they've totally eliminated the guesswork. With confidence I suggest you go for it.
     
  7. Insaneclimber

    Insaneclimber New Member

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    Its not a road bike you moron, choose the width that suits your rideing style and don't listen to roadies.
     
  8. Paulie-AU

    Paulie-AU New Member

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    Yeah good call mate.

    Considering a MTB has a triple chainring that most hackers insist on using every available gear then chainline is important. Also due to the Granny ring many MTB suffer from terrible chainline on the bigring, and pretty ordinary on the middle ring. A longer offset on the drive side compounds the problem.

    On a MTB more control will be gained from stem length and bar width than the couple of mm you would pick up on a BB width that roots your chainline.

    The assumption of me being a pure roadie comes from where?
     
  9. Insaneclimber

    Insaneclimber New Member

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    The fact that your talking total crap,

    Why do they make 118mm bb then smarty, you obviously dont understand chain line LMAO:D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D
     
  10. bikingmat81

    bikingmat81 New Member

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    Well, that's a big plus in my books. That's the set I'm going to go with, if everything I need is there for the install. Thanks for your help. :cool:
     
  11. Paulie-AU

    Paulie-AU New Member

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    Would have to do with manufacturers supplying a frame with wider rear tyre clearance which can then impact on the clearance for chainrings. On dual suspension frames they try and minimise the effect by running a longer chainstay (seeing as typically bikes needing big tyre clearance tend to benefit from a longer wheelbase due to the riding type) and attempt to provide better clearance on the driveside of the swingarm. Manufacturers then make BB to suit these bikes.



    It should be noted if you set up the shimano 2 piece cranks (or raceface for that matter) and don't actually pay attention to your bikes specific chainline you can get a horrible chainline and shifting that reflects that. This can be despite following the “instructions.”



    At no point did I state don't run a 118 if your bike needs to run a 118. I said make chainline a priority, as it would gain more than any perceived handling improvement. Selection of a stem length and bar width applicable to the type of riding to be undertaken will take care of any handling issues.
     
  12. Insaneclimber

    Insaneclimber New Member

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    I cant keep this up im laughing too much

    You made some good points there and i agree with you but there is one point your missing, the main point for the creation of the isis system was to allow riders to choose between 3 different foot spaceings. Your forgetting i think that most (except XC riders) only run 2 sprockets and a bash guard. the other point i think your missing is that a modern 9 spd chain such as xtr will handle the angle created useing a 118 bb. im not saying its perfect, but i am certian that the modern 9spd setup is made to handle it. Good argument there man i look foward to our next crossing. Keep smileing
     
  13. hd reynolds

    hd reynolds New Member

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    I think the point is moot. If one is trying to slap on a crankset on the same BB axle (square in this case) then you might have a problem with chainline ie. the chainrings might rub on the stays or the crank may be too far outward.

    However, given that the BB shell is fixed (68mm in this case) as is the rear dropout gap (135mm mtb), manufacturers nowadays make specific BBs for their cranks that it will seat perfectly resulting in the best possible chainline regardless of how long the stays are.
    Conclusion: Pay attention that you are getting the crank/BB axle set by the manufacturer and you can forget about chainline issues.

     
  14. Paulie-AU

    Paulie-AU New Member

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    Personally I fail to see the benefit of having a wider foot stance over a better chainline. Ultimately frame manufacturers would get it perfect everytime. Actually you would think that they would have figured it out by now. I guess the wider rear hubs speced in new generation DH bikes (V10 etc) attempt to move the cassette wider for better chainline whilst allowing room for chainguides and wider rear pivot spacing.

    Personally on my 3 MTB's only one has a tripple ring (and that is because I haven't got around to ditching the granny), one is a single speed and the other runs a single front chainring with 9speed on the back.

    Recently a new XC bike was purchased for my other half, and the chainline is pretty ordinary considering the quality of the bike. It isn't a massive problem for her because she never uses big ring, that said she never uses granny either and the chainline for the middle ring isn't great. It could definately be improved.
     
  15. bigpedaler

    bigpedaler New Member

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    LET'S PULL BACK A SEC....

    ISIS was created to give mtb riders an alternative to Shimano Octalink, as the old square taper was showing its age and weaknesses.

    118 BB axle length is a DH item. put it on an XC bike, and yeah, you'll have problems. for XC, both Octalink and ISIS go with 113, and chainline issues are pretty small.

    "X-type", the outboard-bearing design (Bullseye original over a decade ago and resurrected by the big S, among others) is significantly stiffer than anything else i've ever ridden 2-2-2 SWEET!! But Octa- and ISIS are still viable choices.

    Price Point provided most of my new parts this year, and the finished product is competitive pricewise with any retailer out there for what i'm riding. i also recommend "greenfishsports.com".
     
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