Viewing 19 posts - 1 through 19 (of 19 total)
  • Why are ISIS Crank / BBs considered a bad idea?
  • DoctorRad
    Free Member

    What was actually wrong with the ISIS standard? Was it that most of the available bottom brackets were awful, or was there something more fundamentally wrong with the design of the standard?

    PJay
    Free Member

    If I remember correctly there was some issues with the spacing of the bearings resulting in rapid wear. Shimano’s Octalink on the other hand was (and is) fantastic; I’ve been running the same XT Octalink cranks & BB for years and they’re both still going strong.

    snotrag
    Full Member

    ISIS resolved the problem at the time of snapping/wearing square taper axles. They did this by making the axle a larger diameter. However this was at the expense of bearings – hence the BB’s just used to wear out very quickly.

    Moving the bearings OUTSIDE of the BB tube eventually resolved that (Hollowtech 2).

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    mindmap3
    Free Member

    It was the BB’s – they just didn’t last. The larger axle and internal BB’s meant that the bearings shrunk compared to the old square taper jobbies. We had two boxes when I worked in a shop – one for dead ISIS BB’s and one for new ones to give to customers when theirs died a few weeks later.

    PJay
    Free Member

    The larger axle and internal BB’s meant that the bearings shrunk compared to the old square taper jobbies

    But I don’t think that this was the wear issue as Octalink had similar axle to bearing ratios and went on forever. When Shimano launched HTII (restoring the square taper axle to bearing ratio) folk started complaining how quickly HTII wore out in comparison.

    DoctorRad
    Free Member

    So a properly designed BB like the SKF one shouldn’t be an issue?

    cookeaa
    Full Member

    IIRC Octalink used a slightly smaller dia axle than ISIS…

    ISIS was essentially what the US/Canadian side of the cycle industry came up with before HT2 as a bit of a consortium/committee, it’s worth noting the next step, to address the bearing issue was “ISIS Overdrive” basically a bigger (Threaded) BB shell that they wanted frame manufacturers to adopt in place of the BSA format… The best thing about it was the “Open Standard” philosophy manufacturing drawings were published for anyone to use, an open design for use by anyone royalty/licence free…

    While the interface was an improvement on square taper, in terms of stiffness and axle strength it was a bit of a bugger to produce in a cost effective way and required some quite fancy forging/swaging tools.

    HT2 splines (and the rest of the crank) are pretty simple to produce by comparison, and lighter, hence ISIS pretty much died.

    hatter
    Full Member

    Hi to all the confused CIA agents reading this thread after it was flagged to them by the system.

    mindmap3
    Free Member

    But I don’t think that this was the wear issue as Octalink had similar axle to bearing ratios and went on forever. When Shimano launched HTII (restoring the square taper axle to bearing ratio) folk started complaining how quickly HTII wore out in comparison.

    I would happily blame the poor BB’s on RF who were an adopter, but neither FSA nor Truvatic managed to make a BB last more than two minutes. I also thought that the Octalink axle was a bit smaller, hence better bearings.

    My HTII BB’s have all lasted really well, well aside from one, a Deore that died after three wet rides. The XT, Saint and XTR ones I’ve had have been great.

    bigyinn
    Free Member

    <div class=”bbp-reply-author”>hatter
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    Hi to all the confused CIA agents reading this thread after it was flagged to them by the system.

    ISIS cranks are the bomb.

    leffeboy
    Full Member

    Was part of the problem not that it required all tolerances to be ‘just so’. If you were slightly out one way the the crank wouldn’t snug in the splines and it would loosen quickly. If you were out the other way then there was to much pressure on the bearings and they died.  HTII solved it with the little plastic preload bolt and then you tightened the crank down independently with the two Allen bolts

    jimoiseau
    Free Member

    Just to bring a bit of balance, I bought a used 2006 bike in 2011 which was still on its original FSA ISIS BB. I then rode it as my only bike for a couple of years, and then as my second bike for a couple of years, then left it in a basement for a few years before transferring all of the parts to a pub bike last year and the BB is still going strong. If it ever goes I’ll replace the cranks, but only because replacement ISIS BBs are expensive now. Maybe I just got lucky.

    Northwind
    Full Member

    What was the Truvativ thing, Isoflow? The one that was like Isis but managed to wear out before you got the bike out of Halfords?

    ssboggy
    Full Member

    Superstar also used to do one that lasted well, I had a couple that easily outlasted the skf ones.

    trail_rat
    Free Member

    Northwind that was powerspline,

    we sold a great number of those, got fed up changing the bbs under warrenty after a matter of weeks that we ended up arguing to new cranks for those lucky customers.

    Phil_H
    Full Member

    ISIS had tiny balls and poor sealing.

    Water ingress turned to rusty balls then crunch crunch.

    Raceface signature ISIS vs UN26 BB

    trail_rat
    Free Member

    Yep i used to have an fsa platinum ti and a fancy raceface isis on rotation with warrenty till they stopped giving me new ones but that bike was doin silly milage.

    Phil_H
    Full Member

    So a properly designed BB like the SKF one shouldn’t be an issue?

    The bearings on the skf one I had were fine. The splines on the axle creaked though.

    The superstar ones had integrated bearing races and bigger balls, so Neil claimed. The cranks i was using snapped after a couple of months so I couldn’t realy comment on the longevity of the superstar bb!

    Speeder
    Full Member

    I quite like them and I’ve got 2 SKF types though they’re both on (very) low mileage bikes (DH & SS) so I can’t really comment on longevity.

Viewing 19 posts - 1 through 19 (of 19 total)

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