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FSA BB-1000/BB-4000 MegaExo Alternative

chrisinleedsukchrisinleedsuk Posts: 106
edited September 2012 in Workshop
My '11 Cannondale Synapse Tiagra is fitted with an FSA BB-4000 MegaExo bottom bracket and it needs replacing. Bearing in mind that FSA BBs are very expensive and not that highly regarded I was wondering if there were any alternatives out there? The sizing is quite odd, whilst it sits on a conventional 68mm BB shell the bore is 19mm as opposed to the more common 24mm and 30mm employed by Shimano and BB30. Any ideas out there?

Posts

  • While they're not particually well regarded, another make alternative isnt likely to be much, if any cheaper .

    Just a quick check for you...do the cranks spin freely ?, no graunchiness ?
    The 19mm bore is because the end seal actually sits in the bearing, its like a top hat shape. The axle actually runs on the plastic end seal, NOT the bearing. What can happen is the top hat section can wear away allowing the cranks to slop about somewhat.
    You can buy replacements for a few quid if your bearings are ok.
  • duplicated post
  • I think these are the ones...
    http://www.jejamescycles.co.uk/fsa-bear ... 60050.html

    If you do go down that road, make sure these are indeed 19mm bore.
  • I've read this a fair few times but in actual fact it's not true. The bearings have a 20mm bore which is sleeved down to 19mm with a metal ring. The plastic top hat is located in the bore but bears no load.
  • Have to disagree with you chris...partly :wink:
    I notice you mention BB1000 in the header, but the post mentions BB4000.
    Unless theyve changed the specs since i did mine (on a BB4000)..yes the bearings are indeed 20mm bore(on mine).
    The sleeve (plastic top hat ) sits in the bearings and the cranks run on that sleeve, not the bearing itself.
    Certainly on mine, there are no, and never were any metal sleeves that bring it down to 19mm, the plastic top hats do that. If you think about it, 20mm bearing, plastic top hat AND a metal sleeve...christ, they'd be very very very thin.
    No load ?....granted the rotating speed isnt that high, but the cranks are nevertheless rotating on, and gradually wearing that plastic top hat. Thats inevitable and why its a [email protected] design.

    No problem anyway, perhaps they have changed (not for the better if thats the case).

    But for those that are interested, what seems like an expensive repair needn't always be...it can be just those top hat washers. Ive been there...ive done it. Its not theory or spouting for the sake of it.
  • I probably didn't explain that too well. On mine the metal sleeve is 20x19x5mm and is pressed into the bore of the 37x20x7mm bearing symmetrically leaving a small recess for the flange of the plastic seal to clip into. I guess it may have been changed so the plastic is no longer a load bearing part except for axial thrust loads.

    I mention the BB-1000 as I think that also has the same external dimensions, I'm just hoping to find an alternative not made by FSA.
  • To the best of my knowledge, unless you change the crankset as well, you're stuck with it unfortunately.
    What crankset are you running...Omega perhaps...thats the only one AFAIK with 19 mm axle. FSA arent even interchangeable within their own ranges. I'm not aware of any other manufacturer doing a 19mm bore BB.

    I gather the BB1000 is 19mm , but its a MTB BB.
    Regarding the metal sleeve, i'm just trying to remember when i did mine if there was a metal sleeve that runs BETWEEN the bearings, not IN the bearings. I might strip mine out tomorrow, just to satisfy my curiosity.
    You are running a road bike ? not MTB. ?

    At the end of the day, its all academic. I dont think you can buy an alterbative BB without replacing your crankset as well. :(
  • I probably didn't explain that too well. On mine the metal sleeve is 20x19x5mm and is pressed into the bore of the 37x20x7mm bearing symmetrically leaving a small recess for the flange of the plastic seal to clip into. I guess it may have been changed so the plastic is no longer a load bearing part except for axial thrust loads.

    I mention the BB-1000 as I think that also has the same external dimensions, I'm just hoping to find an alternative not made by FSA.
    Funny how you read something sometimes ...and dont see whats being said until you read it again.
    The 2mm difference between bearing width and sleeve width, allowing the plastic seal to clip in, and the support of the crank on a metal surface instead of plastic....i can visualise it perfectly now, and its definately different to my BB4000, a design change for the better (despite my earlier statement).
    That said, the BB doesnt seem much better and that may be because the bearings they use are cheap uncaged ones, the balls are free running in the race, not supported in a cage.
    I'm just rabbiting now :wink: (partly for the sake of anyone who's interested in these BBs), IIRC mine only did circa 1200 miles before it gave problems, i replaced the bearings but maintenance is my job so making a press wasnt any bother.
    I did the homework at the time but didnt find an alternative 19mm BB, if thats changed or someone knows better, i'd probably replace mine as well.
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