Viewing 24 posts - 1 through 24 (of 24 total)
  • Bugger – 6mm 6805s
  • coffeeking
    Free Member

    Took my BB apart. 6mm bearings. Arse. Probably easier to machine out the cups than find cheap 6mm bearings.

    Bugger. Again.

    MrOvershoot
    Full Member

    Pete I think you will find all those listed are the industry standard 7mm width 61805 bearings.
    For a while Shimamo used a hybrid 61805 bearing that was only 6mm width.

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    coffeeking
    Free Member

    Can't even machine out the cup, too little metal available. Looks like new BB time 🙁

    petetheplumber
    Free Member

    Can't you file 0.5mm of each side of the bearing?

    coffeeking
    Free Member

    😀 no, it'd screw up the seal location points unfortunately, I'd been thinking of that myself lol.

    coffeeking
    Free Member

    Anyone know of the SSC BBs use 6 or 7mm bearings? If the cups are suitable for replacements later I could be happy to risk the apparently very variable lifespan. Plus if it only lasts a few months I'll return it each time for a new one! 🙂

    Onzadog
    Free Member

    I thought you could use the 7mm bearings in the old cups, it just meant that you couldn't keep the tophats.

    coatesy
    Free Member

    But if you don't have the top hats then the axle will rattle around like a 3month old ISIS.If it's Shimano type where you can slide the crank in and out rather than tightening it agains a stop, is it going to be a problem having slightly wider bearings anyway(other than the top hats not sitting flush.

    jamie@balfa
    Free Member

    Buy something with easily replaceable bearings like Hope or with serviceable bearings like Acros.

    J

    bigyinn
    Free Member

    IIRC SSC use 7mm bearings, but the bearings they use are pish. Sealing wasnt great and died a death pretty quickly in comparison to Shimano ones.
    However, i kept the cups and when i get round to it will get some more replacement quality bearings and bosh them in there.

    thisisnotaspoon
    Free Member

    there must ba a market for a set of cups that only work with 68mm BB shells, but use the extra 7.5mm to fit bigger bearings? Could probably even fit a needle bearing on the drive side which would last ages.

    clubber
    Free Member

    I'm another one who bought the SSC BB simply because the bearings are the standard size making them easy to replace when necessary and wasn't bothered about the oft quoted poor bearing life. That said, I've actually been pleasantly suprised so far in that they've managed a few rides including a very wet Bristol Bikefest with no problems though I wouldn't touch SSC again after Neil/Fruit/TangoBravo's antics on here.

    TheLittlestHobo
    Free Member

    I have the ssc cups running ebay bearings at £2.50 a shot so i made up two sets of cups for £10. They are lasting just as well as ssc and shimano bearings have for me and tbh, at that cost, i dont care. 5min job to replace.

    The BIG bonus though is that the Ebay baerings allow me to keep running the SSC plastic top hat. After seeing what an enduro bearing did to my old LX cranks i wont use that method again. Metal on metal is no a good idea imo.

    coffeeking
    Free Member

    Cheers all!

    clubber
    Free Member

    Metal on metal is no a good idea imo.

    Seems to work for most non-cup/cone hubs not to mention any number of other applications… I suspect that your issue is with the way it's implemented…

    thisisnotaspoon
    Free Member

    The SSC spacers do seem tougher (or at least softer) than the shimano ones so don't feel like they'r about to snap when you press them in.

    As for the metal on metal godd idea/bad idea debate. Its a good idea (it works in every other aplication). But only if shimano machined the axels perfectly and the tolerances were tighter. If it were me designing it from scratch I'd go back to a 3-piece system like euro/ammerican BMX's (massive BB bearings either pressed into the frame or into cups into the frame). Pretty much how laperier are doing it. Or just adjust the ISIS standard to accomodate external bearings (much longer axle lengths but straigher cranks to keep the q-factor the same) like truvative (or was it FSA?) did initialy.

    TheLittlestHobo
    Free Member

    How are you suggesting it was implemented wrong clubber?

    clubber
    Free Member

    Well, fundamentally, external BB chainsets are all designed to be used with existing BBs which all (except a few like Hope who don't actually make chainsets) use plastic spacers to allow for misalignment and also to allow the chainset to fit easily (eg it just slides through the BB – compare to say replacing bearings on a hope hub where you have to hammer the axle onto the bearings or visa versa).

    If external BBs were designed to be used on properly faced and aligned BB threads (note, not the same as 'facing' which only ensures that each side of the BB's face is in line with the threads on that side rather than ensuring that the BB threads are perfectly aligned on both sides) and also a much tigher/interference fit (requiring fitting the chainset with a hammer basically) so that there was no movement between the BB bearing and the axle then metal on metal would be fine and preferable really.

    All the current designs compromise to ensure easier fitting and less requirement for tight tolerances and proper facing/thread alignment which incidentally is fine by me as it does seem to work ok IME in the real world.

    TheLittlestHobo
    Free Member

    So your saying that the plastic spacers (The ones the axle run on) are there because they have decided to design things to a slacker tolerance than they should have. Therefore if you run the metal on metal, you may actually be asking for trouble as the top hats protect the axle. I,e what i said in the first place.

    Another thing the plastic top hat protects against is when the bearing is coming towards the end of its life and isnt spinning as freely as it should. A siexed bearing makes a mess of the axle if the top hat isnt in place. Therefore i stand by my first comment.

    thisisnotaspoon
    Free Member

    Your both right, although IMO the BMX system manages without because the axles are machined much better (and do require fititng with a rubber mallet).

    sharkbait
    Free Member

    Do BMX bikes run through the same mud and carp that MTB do? If not the BMX BB should always last much longer anway.

    clubber
    Free Member

    they have decided to design things to a slacker tolerance than they should have

    I didn't say "should", in fact, I said that I agree with them designing it slacker for real world ease of use (I love that you can remove the chainset with just an allen key). It's a question of what you're trying to achieve. The problem with external BBs compared to cartridge ones (eg ISIS or most square taper) is that you're reliant on the BB shell for alignment which the BB/chainset manufacturer can't control.

    In your example about the seized bearing, if you've got a tight fit (like on a hub) even a very worn bearing will still turn because it has to (the inner race won't easily move in relation to the chainset axle) so you'll just knacker the bearing more and more, not the axle. The problem you're on about is where you're using a metal/metal contact without designing in a tight fit (eg the Hope bearings which still allow the chainset axle to slide through pretty easily).

    coffeeking
    Free Member

    I'm perfectly happy to sacrifice bearing life (within reason) for ease of chainset removal – if the bearigns are a fiver a year then that suits me down to the ground. If they expect me to replace my set of cups because their bearing sealing failed, then I'm not so happy. But I agree,it's designed for use and fitting, rather as the perfect engineering solution. Ground axles and interference fits would be lovely if we all owned a press and bearing splitting tools, but they have to compromise somewhere.

    So long as the SSC cups take 7mm bearings I'll take my chances.

Viewing 24 posts - 1 through 24 (of 24 total)

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