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  1. #1
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    Compatibility between “Shimano ISIS” and Raceface ISIS

    Hey experts,

    I am considering purchasing a used frame with a Raceface XS bottom bracket already installed. I am wondering whether my Shimano ISIS crankset will fit these splines. Someone pointed out today that they might not.

    My crank: “Custom Shimano Hollowtech, Octalink XT Spline:

    If anyone has any information on this, thanks!

    Thanks!

  2. #2
    JMH
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    Octalink and ISIS are different

    They are not compatible.

    Octalink is Shimano's standard... ISIS is used by others, including Raceface.

    Sorry!

    JMH

    Quote Originally Posted by Bloodfist
    Hey experts,

    I am considering purchasing a used frame with a Raceface XS bottom bracket already installed. I am wondering whether my Shimano ISIS crankset will fit these splines. Someone pointed out today that they might not.

    My crank: “Custom Shimano Hollowtech, Octalink XT Spline:

    If anyone has any information on this, thanks!

    Thanks!

  3. #3
    Chrome Toaster
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    They look similar and follow the same concept but are completely different and incompatible. Octalink uses 8 straight and short splines. ISIS has 10 splines with longer depth and tapered towards the end.

  4. #4
    Doesntplaywellwithmorons!
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    Actually Octalink is tapered and ISIS isn't (it uses a hard edge to limit how far the cranks are installed). ISIS was an attempt at bypassing shimano's patent (the 8 spline pattern they use is patented, and shimano has only ever licensed FSA to make BB's using the pattern for OEM sales only...like to Santana for tandems... never to anyone for aftermarket sales) which raceface, FSA, truvativ and others tried rushing to the marketplace to play catchup (shimano had splined BB's for 5 years before ISIS came along). In like 6 months the things went from tradeshow idea to production status. And 6 months after that all the complaints started piling up about the crappy bearing durability.

    The reason they sucked is because as they were trying to catch up to shimano, they took a lot of shortcuts. One was trying to get it to market across several price ranges at once. Another was deciding to rely on off the shelf cartridge bearing options to fit the oversized spindles (which were still limited on the physical size of the BB shell as to how much space you had for the bearings) and to speed up develop time. Shimano never does anything quick which is why most things they produce are so good from the start. They spend YEARS on R&D for most things, and bring it to just one component group at a time to begin with, to make sure it works in the real world as well as it did in the R&D world.

    Shimano brought Octalink BBs/Cranks to XTR in 1996, DuraAce in 1997, Ultegra 600 in 1998, 105SC in 1999, Deore LX/XT in 2000, Deore in 2001. And the first XTR BB's set the pattern for what type of bearings all the rest would use as well... needle bearings (which are really small in diameter but about a half inch long) to handle the vertical loads as the spindle is turning, and ball bearings to handle the side loads from the rider flexing the cranks as he/she pedals. All the ISIS idiots tried to just use ball bearings to handle both loads, but they went with balls as small as shimano used JUST for the side loads.

    Skip ahead a few years, and shimano brings out external bearing setups and all the former ISIS proponents are copying them again, and largely abandoning ISIS after they spent so much time trying to convince consumers to buy their components instead of shimano's. And unfortunetly, this has shafted a lot of consumers as choices for ISIS BBs/Cranks have shrunk, when they need something replaced. Shimano at least still supports BB designs they were using 20 years ago in some manner, even if not with as much flash and fanciness as originally.
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  5. #5
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    Thanks for your explanations guys. Now that you put it this way, I don't even know why I thought the two would be compatible in the first place.

  6. #6
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    Quote Originally Posted by DeeEight
    Actually Octalink is tapered and ISIS isn't (it uses a hard edge to limit how far the cranks are installed).
    I was just refering to the spline design because its easy to identify. Yeah Octalink has a very shallow taper but its on the spindle itself. The splines are square and straight. ISIS has a very pronounced taper at the end of the spline which is very easy to identify because of the rounded off inside edges. This is supposed to really pinch down the crank before it does the hard bottom out on the stoper. It also insures you also nearly break your torque wrench in order to get the cranks to bottom out on the spindle. One of the more annoying aspects of ISIS installation.

  7. #7
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    Quote Originally Posted by DeeEight
    Actually Octalink is tapered and ISIS isn't (it uses a hard edge to limit how far the cranks are installed).....
    My recollection of reading the standards was that ISIS was tapered and had an interference fit, while Octalink was not. Poor tolerances ment that some combinations of ISIS BBs & cranks didnot interfere properly, and infact some were loose right from the start. Octalink on the other hand is very prone to creaking since there is no interference taper. Both use a hard stop.

    Quote Originally Posted by DeeEight
    Shimano brought Octalink BBs/Cranks to XTR in 1996, DuraAce in 1997, Ultegra 600 in 1998, 105SC in 1999, Deore LX/XT in 2000, Deore in 2001. And the first XTR BB's set the pattern for what type of bearings all the rest would use as well... needle bearings...
    I think only the original XTR & DuraAce used roller bearings, all others (including, as far as I know, later XTRs) only used balls. Shimano ground the races into the axle, which allows the use of larger balls (compared to using cartridge bearings).

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