BSA to bb 386 evo conversion for fsa sl k light

ArgonDon
ArgonDon Posts: 16
edited December 2013 in Workshop
Hi I have a standard English thread BSA bottom bracket, I want to fit a FSA SL K 386 crank to it, off the back of a number of adverts etc I purchased this
TRiPEAK BB386 Bottom Bracket For BSA Threaded Frames, problem is that although it all fits, when you tighten the crank, keeping the steel washer on the non drive side, the crank pretty much locks solid, if I back it off to allow it to rotate freely, the crank arm will wobble/ flex on the non drive side, I'm worried that if I do it "just tight enough" I'll either loose power as too tight . Or it will fall off as it slackens, any advice, or anyone been here before, and please no smart comments about sticking to what the frame was designed for, I'm regretting the whole setup already!

Thanks
Don

Comments

  • simonj
    simonj Posts: 346
    On the megaexo cranks the bb for the fsa carbon crank was different to the alloy crank as the carbon one was slightly thinner. This meant you can use standard Shimano hollow ii bb on the alloy cranks but not the carbon ones as they had too much preload. Not sure about bb386, but what you describe sounds simular. I take it you have tightened up the bb into the frame enough? Also is there a reason you did not get the FSA megaevo bb @ £35, the tripeak one at planet x is £5 more than the standard fsa one :-

    http://www.planet-x-bikes.co.uk/i/q/BBF ... om_bracket
  • papavero
    papavero Posts: 57
    The crank arm bolt needs to be torqued to 40Nm otherwise the left crank arm will be loose.

    Sounds like the BB cups are too far apart, as simonj said make sure that they are screwed in properly, it may be that you need to 'face' the frame to get the correct distance between them.

    By 'steel washer' do you mean the wave spring that slides over the axle between the BB and left hand crank? All it is there for is to take out any float caused by the gap between the arm and bearing. The gap is there to allow for manufacturing tolerance. Sounds like you don't have a gap there so try discarding the washer.
  • ArgonDon
    ArgonDon Posts: 16
    First off thanks to you both for commenting, Simon, think you have got my meaning slightly wrong, the link you give is for a standard Bb30 bracket not a bsa to bb30/386 "conversion"
    Papavero, I should have said that I'd tried without the float washer still doesn't help, but thanks for the torque heads up, I think the issue is that the tripeak is to give a BB length of 68.5 whereas standard bsa bracket is 68 dead, does this sound right, Planet X are looking into this for me as they haven't sold many (0) and they spotted the discrepancy, so may not do what it says on the box!
    Don
  • simonj
    simonj Posts: 346
    No don't think I got what you meant wrong, but the Planet X title is misleading, as they only mention the pressfit, but in the listing it has the pf and the BSA version. If you look at the picture of the green bottom bracket very closely it looks like it is a megaevo at £35 not pressfit at £100 as per fsa's website, ie to fit a 386evo into a BSA frame. Planet X say its a megaexo bb386 but there's no such thing, but there is a megaevo bb386

    http://www.fullspeedahead.com/products/783/MEGAEVO

    The fsa website describes it as 68mm, so may be of luck, anyway hope it helps.
  • ArgonDon
    ArgonDon Posts: 16
    Hi Simon, owe you an apology, didn't read the details in the link properly, I think you may be spot on, I'll wait for Planet X to come back to me, point that out and see if I can get am deal from them, cheers
    Don
  • papavero
    papavero Posts: 57
    A standard BSA BB shell is 68mm wide
    A 386 evo BB shell is 86.5mm wide

    When your adapters are screwed into the frame the outside faces of the bearings should be 86.5 mm apart
    When assembled the distance between the inside faces of the crank arms should be around 90mm.
    The difference between the bearing and crank dimensions is made up with shims/wave spring.
    Do a bit of measuring to work out where the problem is.
  • ArgonDon
    ArgonDon Posts: 16
    And there's the problem, when screwed together the o/s faces come in at 90-91mm, there is no gap between the inside faces and the frame so it must be that the bearings themselves are too wide thanks for your help back to Planet X !
  • ArgonDon
    ArgonDon Posts: 16
    So just as an update in case anyone else has the same problem, the Fsa Bb does what it says it all fits the TriPeak ones are wider by 2mm each and don't fit, thank you for your help, esp Papavero with the relevant dims, made it easy to work out, and Simon for the link to the Fsa brackets
    Cheers
    Don :D
  • papavero
    papavero Posts: 57
    Makes you wonder what they have been smoking at TriPeak!
    Glad it all worked out in the end

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