Isis vs square-taper for SS- Mtbr.com
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  1. #1
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    Isis vs square-taper for SS

    i have a choice of an Isis and a st bottom bracket for my rigid SS. i know Isis are known to blow bearings but are supposedly stiffer than ST brackets. which trade-off is worthwhile?

    which BB's are cheaper to replace?

    can i simply replace the bearing cartridges on an Isis BB when they blow or do i have to buy a whole new BB?

  2. #2
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    If your bike has an EBB, ISIS is the way to go you don't have to worry about wearing out the taper. That is if you change ratios alot.
    Last edited by ne_dan; 12-11-2009 at 10:47 PM.

  3. #3
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    Do you think you will feel the difference between the two? Anyway, the Isis isn't able to be serviced ( to my knowledge). I like durability. Isis cranks last longer.
    milesW

  4. #4
    Retro Grouch
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    Quote Originally Posted by ne_dan
    If your bike has an EBB, ISIS is the way to go you don't have to worry about wearing out the taper. That is if you change ratios alot.
    Huh??? Once a bottom bracket is installed in the EBB body, there is no reason to remove the crank arms to adjust the chain tension. I don't understand your logic.
    Just one more rep and I get the toaster!

  5. #5
    Out spokin'
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    Quote Originally Posted by miles wadsworth
    ... Isis cranks last longer.
    May I ask what makes you say this? I have square taper cranks (195mm length, as well as others) that I've been runnin since 1994... other length cranks that are older but I can't pin down the date...

    Personally I've never found a reason to abandon square taper cranks. I'm not saying they're better than ISIS because I've never used ISIS so I can't say there's anything wrong with ISIS. But I can certainly say there's nothing wrong with square taper. They will last for years and years -- I've never worn a square taper out (broken the arms, but never the taper) and my off-road riding experience goes back to '85.

    No way they flex too much -- remember I run 195mm arms. That's about an inch longer than 175mm arms (the world's "standard" length), so if anyone would detect excessive flex, I think it would be someone running XL long cranks such as myself.

    --Sparty
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  6. #6
    Paste eater
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    I've toasted so many isis BB on a SS. ANything but ISIS if you ask me.

  7. #7
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    Quote Originally Posted by mack_turtle
    i have a choice of an Isis and a st bottom bracket for my rigid SS. i know Isis are known to blow bearings but are supposedly stiffer than ST brackets. which trade-off is worthwhile?

    which BB's are cheaper to replace?

    can i simply replace the bearing cartridges on an Isis BB when they blow or do i have to buy a whole new BB?
    Isis (and octalink) will be a forgotten and regretted chapter in the history of bikes. Square taper has lasted through the ages and I expect X-type to last well also, but I see no reason to consider ISIS in this day and age, it was a mistake
    Last edited by DanD; 12-12-2009 at 01:47 PM.

  8. #8
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    Square Taper.

    I've always run square taper and they just work. ISIS is indeed a forgotten standard.

    Just pulled my cranks for some yearly EBB maintenace (removing/cleaning of the threads of the bushnell and regreasing) and the BB still runs super smooth after 3 years of regular/daily use. BBun-73..

  9. #9
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    I use square taper as well, and I run 195mm, just like Sparty. No flex, no issues. Unless you have a set of ISIS cranks lying around, forget about them.

  10. #10
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    Quote Originally Posted by aka brad
    Huh??? Once a bottom bracket is installed in the EBB body, there is no reason to remove the crank arms to adjust the chain tension. I don't understand your logic.

    if you change ratios a lot....the other poster said... changing the rear cog would lead you to adjusting the ebb.
    Sette Reken "Hopper" SS

  11. #11
    CB2
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    I'm a smaller guy @ 135-140 lbs, so flex was never too much of an issue for me, but square taper is the standard for track racing, and some of those guys are just monsters. If flex was an issue, I'm sure they'd find a different solution at this point (when there are so many other options).
    I did switch to ISIS, because that's what I had available for cranks at the time and have been happy with the BB's longevity and performance.
    My last square taper's were Raceface Turbine LP's which I loved, but wore out from removing too often searching for a creak.

  12. #12
    singletrack bound
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    I've gone back to squares and had forgotten how reliable they can be. 29ss eno crank 175
    no noises or bearing resistance. In the stand they spin freely and on the trail run smoothly.Inexpensive UN-73 Shimano Square Taper bottom bracket.

  13. #13
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    Yes, but when adjusting an EBB, you don't have to remove the crank.



    Quote Originally Posted by joshik123
    if you change ratios a lot....the other poster said... changing the rear cog would lead you to adjusting the ebb.

  14. #14
    AZ
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    Square taper , time tested goodness .

  15. #15
    Tulsa
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    back to square after trying the other options
    wherever you go, there you are

  16. #16
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    I run both and I think ISIS is a bit stiffer.

    On the downside: ISIS bearings actually wear out a bit faster because they are smaller. Unless you buy some quality SKF bottom bracket. I am lucky because my FSA ISIS BB didn't give up yet after nearly 4 years of use. Other ISIS BBs I used broke down after a few rides.

    No square taper BB failed me yet. In one of my bikes a cheap one (bb un52) has been working flawlessly since 1998.

  17. #17
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    For ISIS go SKF

    The all stainless SKF ISIS BB's are bulletproof if the FR600 version I have is anything to go by. I've been using mine for 4 or 5 years now, it's been on 4 different bikes and has never missed a beat. Still running silky smooth as if it was first day of purchase.

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