So I took the old bottom bracket out of my hybrid frame, FSA Platinum ISIS Bottom Bracket 68 x 118mm.

I then replaced with a Shimano BBUN55 Square Taper 68 x 11.8cm. Then realised that this was a square taper, not the star shaped of the previous FSA. Now obviously my crankset won't fit.

Happy to purchase another crankset, as mine has 6,000km+ of hard way & I really don't fancy taking it back out again.

Would something like: http://www.chainreactioncycles.com/fsa-vero-compact-n10-11-chainset/rp-prod129455 fit?

Otherwise, should I take it out and order the correct one? The only BB I can see if the same one, and they only seem to last 3,000km :(

  • 1
    Well, the star is generally considered superior to the square (though I'm not racing to replace my square taper unit). (If a BB cartridge only lasts 3000km there's something seriously wrong with it, and I don't recall any other complaints here about Shimano BB carts wearing out that fast.) – Daniel R Hicks Sep 20 '15 at 12:11
  • Thanks for your comment, its the FSA Platinum ISIS Bottom Bracket that keeps dying on me. Seems to be a common flaw, and they get awful reviews (and common on this boardman hybrid). – AliGibbs Sep 20 '15 at 12:28
  • OK, so the star pattern is not compatible with Shimano? (I think some are, some aren't.) – Daniel R Hicks Sep 20 '15 at 12:34
  • I didn't even think to check! Just looked so different, I didn't even try. Will go check shortly. – AliGibbs Sep 20 '15 at 13:21
  • ISIS is basically splined cranks which are an alternative to Shimano Octalink and not are compatible (10 splines vs 8 splines). That looks like a fine square taper crankset, but you need to make sure your BB gives you the right chainline and what not. – Batman Sep 20 '15 at 21:01

I'd consider going back to square taper a bit of a downgrade. And buying a crank to suit the bottom bracket is a little bit backwards in thinking. That crankset you linked to would be fine assuming you want to keep the BB. FSA has been pretty good in my experience, but I can't say that with certainty for your case because I've only dealt with their more expensive stuff.

The thing you'll have to watch out for is getting the right chainline. If you have the wrong length spindle, you'll end up shimming something, which I never recommend unless absolutely necessary, or just buying a new one anyways. Without more information I couldn't make an assessment of the right length spindle for your bike. I didn't have any luck on FSA's website in finding their suggested spindle length to produce the standard 43.5 mm chainline, or whatever is appropriate for your case.

I would go order the correct BB if I was you, as long as you're willing to keep your crank for a little while longer. A new crank AND BB might be in order if you can afford it and want a smooth new setup. I don't know what you're doing though if those FSA BBs are only lasting 3000 km, though. I've had that exact same one, and it lasted so long I sold the bike before it wore out.

  • This is my 3rd BB of this type. My friend has the same bike, has also gone through 2 as well. Either they aren't used to the welsh weather, or we are really hammering our bikes? I have gone with the correct BB- will report back in about 6 months :-P – AliGibbs Oct 5 '15 at 10:06

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