BB86 and FSA K-force Crank - Bearing options?

AlainR
AlainR Posts: 88
edited March 2010 in Workshop
First of all, hello (newbie on here....)

I've got a question abotu BB86 bearing options when fitting and FSA K-Force carbon compact crank.

The frame: 2009 Giant TCR advanced
Bottom Bracket shell width: 86.5mm
Bottom Bracket shell type: BB86 (press fit)
Current Crank setup: Shimano 105 Hollowtech II, with Shimano BB86 bearings
New crank setup: FSA K-force, as purchased from Planet X (with a Mega Exo BB setup)
Road use. Integrated MegaExo BB, monocoque crankarm/spider and precision CNC machined 7075/T6 chainrings, ramped and pinned for perfect shifting.

AL7075 Torx T-30 alloy chainring bolts
MegaExo oversize cartridge bearings
Oversize splined integrated chromoly BB axle
MegaExo alloy bearing cups with 24mm spindle
BCD - 110mm
Q-Factor - 147mm
Chainline - 43.5mm
Weight - 705g
Arm Length - 175mm
Chainrings - 34/50T

No as far as I understand, FSA do a BB86 bearing kit to suit (ceramic), but also like £120+ for it. Enduro Zero also offer a BB86 bearing kit for ~$90, but only offer it as either Shimano or SRAM, neither or which do I know will work.

Has anyone got a similar setup, or know what the options are?

Would it be most wise just to fork out for the FSA option, in the hope that the guaranteed fit is worth it?

Thank you, in advance! :)

Comments

  • maddog 2
    maddog 2 Posts: 8,114
    I have the same frame.

    This all comes down to whether the FSA K-Force cranks fit the Shimano cups. Some FSA cranks do and some don't. Try a forum search to confirm that but I suspect they need slightly narrower cups. In which case you need either the FSA cups, or ask Enduro to fabricate you some cups to fit the K-Force cranks.

    I use the hybrid ceramic Enduro cups on a SRAM red setup, and they are very well made and smooth. The website might not list the GXP cups but they definitely do them.

    http://www.enduroforkseals.com/id258.html

    You could email them and ask them about the compatibility with the K-Force crank. They were helpful with me.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • AlainR
    AlainR Posts: 88
    Cheers :)

    Presumably the over all cup width differs due to the shoulder on the actual insert?

    I'm guessing it's no more than circa a mm in difference, but enough to cause issues when you torque the crank arm up, is that right?
  • maddog 2
    maddog 2 Posts: 8,114
    difficult to say, as I've not owned a mega exo FSA c/set so I'm not 100% on how they preload the bearings.

    On a Shimano setup the bearing width isn't super crucial as the non-driveside arm slides on as is preloaded by the mechanic, so if the bearings are a tad 'fat' then the arm just slides on a bit less. The FSA system has a bolt on the end I think, so if it works in a similar manner to SRAM's GXP system, then the NDS crank arm will 'lock' against the NDS bearing and leave the DS bearing to 'float'.

    If this is the case then having too-wide bearings may be a problem - when you tighten up the crank bolt it may try to squash the DS bearing, which would cause friction and premature wear.

    If the K-force cups are only a few mil narrower than the Shimano ones then you'll probably get away with it, so intitially I'd be tempted to fit the K-Force crank to you current Shimano BB and see how it goes. You may find it slots in no problem.


    If it doesn't work then it sounds like you'll need specific K-force cups.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • redddraggon
    redddraggon Posts: 10,862
    I'm near certain K force take a slightly narrower BB. The FSA method is near exactly the same as Shimano, but I wouldn't risk trying to use the same BB.

    Another issue is that when you use an FSA chainset on a shimano ht2 BB, it's not a simple slip on, like it would be with a HT2 crank. They are compatible but an FSA chainset is a tight fight with a ht2 BB, and takes quite a bit of force to get on, I use a ht2 BB with 2 fsa chainsets fine othersize. I wouldn't want to try forcing it on an expensive frame and chainset though.
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  • maddog 2
    maddog 2 Posts: 8,114
    how does the FSA preload the bearings then red?
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • redddraggon
    redddraggon Posts: 10,862
    With a bolt on the end like Shimano, except you use an allen key instead of a dodgy star shaped thing
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  • bigmat
    bigmat Posts: 5,134
    I don't really know what I'm talking about, but I have used an FSA SLK carbon crankset with a Shimano bottom bracket and currently a Miche (I think) bottom bracket, without any isue that I'm aware of.
  • redddraggon
    redddraggon Posts: 10,862
    MatHammond wrote:
    I don't really know what I'm talking about, but I have used an FSA SLK carbon crankset with a Shimano bottom bracket and currently a Miche (I think) bottom bracket, without any isue that I'm aware of.

    Higher level FSA chainsets take narrower cups, while lower level chainsets take shimano width cups.
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  • AlainR
    AlainR Posts: 88
    Cheers guys.

    I trial fitted it today, and it looks llike it would fit, but there's no receess in the HT2 BB for the fibre /steel washer that fits between the crank arm and BB, so you'd basically be forcing it into the BB.... probbaly not ideal.

    I did have a bit of a panic though, as the left crank arm took a fair bit of force to get on (sounds llike this might be normal?), so removing it was somewhat interestinig!

    Never the less it looks like the only option might be to fork out for the right bearings :(