Bottom brackets - a bit confused!

Rhods Posts: 400
edited April 2010 in Workshop

I am currently in the process of sourcing parts for a build I am hoping to complete. If all goes to plan, it will be on a Dolan Hercules.

The spec states that the bottom bracket is an english thread. But, what does that mean?!

I currently have tiagra with external bearings. Is this the type of thing that's needed for the Dolan? I have my eye on an FSA chainset, but that has ISIS bottom bracket. Will this fit?

Could someone please tell me what my options are?

Many thanks


  • teulk
    teulk Posts: 557
    Now let me see if i get this the right way around - English Thread, drive side has a reverse thread, Italian Threat, drive side is a normal sure some one will correct me if im wrong in my thinking.
    Boardman Team 09 HT
    Orbea Aqua TTG CT 2010
    Specialized Secteur Elite 2011
  • Rhods
    Rhods Posts: 400

    That much I think I've got! As long as you get the size correct can you then put any type of bottom bracket on the bike? i.e. whatever's required to fit your chainset of choice?
  • Monty Dog
    Monty Dog Posts: 20,614
    As long as you have the matching English-threaded BB for your chainset, you can fit any one you like. FWIW these days there are only 2 thread standards for BBs - English or Italian - all the others are pretty well obsolete.
    Make mine an Italian, with Campagnolo on the side..
  • Rhods
    Rhods Posts: 400
    Great. Thanks.

    To a more specific question, how do people rate the ISIS bottom bracket and what tools do you need to maintain it? I'm currently using Hollowtech ii.

  • schweiz
    schweiz Posts: 1,644
    An ISIS BB (or octalink in Shimano speak) has a larger spindle than a traditional square taper BB but still has internal bearings. Therefore the bearings are smaller and are less durable. This 'flaw' was probably the driving force for external BB bearings which allow a large spindle and larger bearings.

    Saying that, this weekend I've just changed my BMC from triple to a double which also meant a new BB. I stuck with the 6500 Ultegra that was originally fitted, mainly due to cost as 3 generation old Ultegra parts can be bought relatively cheaply.

    The BB that I took out is still running smoothly after 10's of thousands of km and 7 years so whether the durability issue affects road bikes, my experience says not.

    Saying that I'd stick with Hollowtech II, purely based on the fact that buying replacement parts in the future will be easier.

    As for maintainability, there is none to do on a sealed BB. Just grease (or copperslip) the threads before installing and away you go.

    Also, for installation, Hollowtech 2 bearings need pre-loading using a tool that costs a couple of quid. Octalink doesn't need anything other than an allen key. The BB shell may also need facing for hollowtech 2 to make sure that the external faces of the BB shell are square to the frame and parallel to each other. This is a job for a bike shop. Internal bearings don't need to have the BB faced.

    The only other thing that you've not considered is the BB width. BBs for triples are wider than for doubles.

    Hope that helps.
  • Rhods
    Rhods Posts: 400
    That's a great help. Thank you.

    Just one more question - do any other manufacturers use the Hollowtech II system (and do they have their own names for it?)

    Please excuse the total ignorance - I've never ventured from Shimano!

  • redddraggon
    redddraggon Posts: 10,862
    Rhods wrote:
    That's a great help. Thank you.

    Just one more question - do any other manufacturers use the Hollowtech II system (and do they have their own names for it?)

    FSA have megaexo, but hollowtech BBs will fit.

    SRAM/Truvativ have GXP, hollowtech BBs are not compatible.

    Campagnolo/Fulcrum have ultra torque, uses external bearings, but the bearings are attached to the axle, and bearingless cups are screwed into the frame
    I like bikes...

  • John.T
    John.T Posts: 3,698
    ISIS BB (or octalink in Shimano speak)
    Isis and Octalink are quite different. Octalink is fairly reliable but Isis has a poor reputation wear.
    If you are building a new bike I would say get external bearings.
  • schweiz
    schweiz Posts: 1,644
    John.T wrote:
    Isis and Octalink are quite different.

    Sorry for any mis-information. The tools to remove an octalink BB seems to be the same as the tool to remove an ISIS BB (mine was labelled as both) and the spindle ends look very similar so never having used an ISIS BB I made the assumption that octalink was a Shimano trademark for ISIS.