Advertise on Bikeforums.net



User Tag List

Results 1 to 15 of 15
  1. #1
    Senior Member powitte's Avatar
    Join Date
    Mar 2008
    Location
    Chicago
    Posts
    179
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    In need of a primer on modern bottom brackets

    I've done quite a bit of work on bicycles, but haven't had any experience with more sophisticated bottom brackets after a Shimano UN-54 I installed several years ago. That BB, and everything I worked on before it, had lots of size options and measurement/calculation was important in getting an appropriate chainline. It also was easier because square taper was most of what was available at my price point.

    Now, I'm just about to start a new build on a Devinci Tosca SL 2 cyclocross frame. I haven't gotten it yet, but I suspect it's a standard BB shell based on the specs, which says the complete bike comes with a Hollowtech II BB. 130mm rear spacing also, if that matters.

    So, here are my questions:
    1) What are some of the more important differences between the various BB designs out there?
    2) Is square taper really that inferior to "outboard" designs? I've done a ton of riding on my 'old fashioned' bottom brackets, without any problems.
    3) How can the user decide what sort of chainline to run with many BBs I've looked at which don't come in different lengths?? For example...

    What all this boils down to is product selection for this build. I'm planning on running a 1x9 setup, not doing any serious competition, just for fun. I'm not picky about high performance, and value (note, 'value' to me does not necessarily mean cheap) is more important that a few grams of weight or bit of extra drag. Recommendations?

  2. #2
    Senior Member
    Join Date
    Sep 2004
    Location
    boston, ma
    Posts
    2,774
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    chainline is fixed for the most part on modern cranks. you have traditional threaded and press fit types. a few different press fit types that revolve around a 24mm spindle or 30mm spindle

  3. #3
    Senior Member powitte's Avatar
    Join Date
    Mar 2008
    Location
    Chicago
    Posts
    179
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by reptilezs View Post
    chainline is fixed for the most part on modern cranks. you have traditional threaded and press fit types. a few different press fit types that revolve around a 24mm spindle or 30mm spindle
    How is that an upgrade--inflexibility in allowing a user to select their chainline?? That just seems foolish to me.

  4. #4
    Senior Member
    Join Date
    Feb 2009
    Posts
    3,954
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by powitte View Post
    How is that an upgrade--inflexibility in allowing a user to select their chainline?? That just seems foolish to me.
    It's all new and improved marketing hype. Each manufacturer is trying to make theirs "stronger, stiffer, lighter" and all of the other catchphrases that sell the stuff. There was nothing wrong with the old square taper system.

  5. #5
    Senior Member powitte's Avatar
    Join Date
    Mar 2008
    Location
    Chicago
    Posts
    179
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by davidad View Post
    It's all new and improved marketing hype. Each manufacturer is trying to make theirs "stronger, stiffer, lighter" and all of the other catchphrases that sell the stuff. There was nothing wrong with the old square taper system.
    That sets my mind at ease. Thanks!

  6. #6
    Senior Member skydog6653's Avatar
    Join Date
    Mar 2009
    Posts
    149
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by powitte View Post
    In need of a primer on modern bottom brackets
    I just use rustoleum

  7. #7
    Senior Member
    Join Date
    Aug 2005
    Location
    Pittsburgh, PA
    My Bikes
    '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
    Posts
    25,260
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    The new external bearing cranks with their built in large diameter hollow spindle are indeed lighter and stiffer than their square taper predecessors. Is that important? Not to me.

    However, they do take the ambiguity out of bb selection because if you use the crank as designed (road cranks on road frames and MTB cranks on MTB frames) the chainline is automatically correct. Do a search here for bottom bracket topics and you will find dozens of "how do I choose the right bb spindle length for my XX crank?" questions. Add in the ISO/JIS semi-mismatch and symetrical vs. unsymetrical spindles and square taper bb's weren't that simple either.

    What is really confusing now is the myriad of new bottom bracket and frame "standards" with several variations on the press fit, thread in, and who knows what's next design.

  8. #8
    biked well well biked's Avatar
    Join Date
    Jul 2005
    Posts
    6,774
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by HillRider View Post
    What is really confusing now is the myriad of new bottom bracket and frame "standards" with several variations on the press fit, thread in, and who knows what's next design.
    Agreed. No question that the newer stuff is lighter and stiffer for the most part, but I've recently counted eight different bottom bracket "standards" in our shop, and I probably missed something.

    The word is that Shimano will introduce cranks with 30mm spindles soon, and that will throw a new twist into the oversized press-fit bb market as well. Just trying to keep up with it all is a challenge.

  9. #9
    Senior Member
    Join Date
    Nov 2010
    Location
    River City, OR
    Posts
    553
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    IMO the advantage in the new BB style is for the manufacturer- not the end user. There is the marketing hype, but also manufacturing costs are less than the "old stuff." For the end user the advantage would be less weight, and lower costs for aftermarket or replacement parts. Ain't nothing wrong with the old square taper, but it's getting expensive, somewhat due to scarcity. Price a Phil bottom bracket and a set of quality cranks. Adds up quick. If weight isn't an issue you can do a UN54, and choose from the huge supply of used square taper cranksets out there. Makes the newer stuff look pretty attractive though.

  10. #10
    Senior Member gyozadude's Avatar
    Join Date
    Jun 2011
    Location
    Sunnyvale, California
    My Bikes
    Bridgestone RB-1, 600, T700, MB-6 w/ Dirt Drops, MB-Zip, Bianchi Limited, Nashbar Hounder
    Posts
    1,183
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I would argue that the cost of a square taper JIS BB has never been cheaper. I can buy today, for $18, a Shimano UN55 which is like the UN54 only with metal cups on both sides and not plastic on one. Sealed cartridge bearings. Pretty darn smooth, and square taper. I can also buy a Vuelta BB in square JIS taper in a variety of widths. Sealed cartridge bearings, steel cups. $14. And I just bought a new Vuelta crank, compact crank set, 50-34 for just $30 and it's square taper. So it's not getting that expensive. It's not super high end, but it works great and it's compatible with Shimano. I picked up an SR cheap XCT v2 crank for around the same price, $30 and it supports a square taper.
    Yes, I can roll my own potsticker skins!

  11. #11
    Senior Member
    Join Date
    Oct 2005
    Location
    Ormond Beach, FL
    My Bikes
    2005 Specialized Roubaix Elite
    Posts
    215
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The current issue of Bicycle Times magazine has a pretty comprehensive article on the features and compatibilities of the current configurations of bottom brackets.

  12. #12
    Senior Member
    Join Date
    Nov 2010
    Location
    River City, OR
    Posts
    553
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by gyozadude View Post
    I would argue that the cost of a square taper JIS BB has never been cheaper. I can buy today, for $18, a Shimano UN55 which is like the UN54 only with metal cups on both sides and not plastic on one. Sealed cartridge bearings. Pretty darn smooth, and square taper. I can also buy a Vuelta BB in square JIS taper in a variety of widths. Sealed cartridge bearings, steel cups. $14. And I just bought a new Vuelta crank, compact crank set, 50-34 for just $30 and it's square taper. So it's not getting that expensive. It's not super high end, but it works great and it's compatible with Shimano. I picked up an SR cheap XCT v2 crank for around the same price, $30 and it supports a square taper.
    No argument here- but there are cases, and if weight is no object I'll choose square taper any day. It's really economical. But in the low weight class square taper BBs and cranks are expensive- more than OB bearing crank.

  13. #13
    Senior Member powitte's Avatar
    Join Date
    Mar 2008
    Location
    Chicago
    Posts
    179
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by reddog3 View Post
    No argument here- but there are cases, and if weight is no object I'll choose square taper any day. It's really economical. But in the low weight class square taper BBs and cranks are expensive- more than OB bearing crank.
    Well, I ended up getting a hollowtech II 105 BB for $20 and a tiagra crankset for $76. Not too bad. Though I'm reading the install details and getting a bit queasy. Do BB shells really have to get machined often???

  14. #14
    Banned
    Join Date
    Jun 2009
    Posts
    4,793
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    BB shell "facing", IF needed at all, is only needed once. Basically, it's to make sure the BB shell is 'square', not lopsided on the exterior contact points with the external BB. The more expensive the frame, the more likely it was factory faced.

    Most often, the "facing" only clears sloppy paint from the frame. Did that myself once with a file, had no issues.

    ONE of my last three frames could have used the facing operation, and only for the external-BB crankset. I've been using an ISIS crankset for two years now, and IMO, it's better than anything external. ISIS and Octalink is where they should have stopped.

  15. #15
    Senior Member commo_soulja's Avatar
    Join Date
    Aug 2008
    Location
    C-Ville
    My Bikes
    are fun to ride
    Posts
    1,144
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Here's a really great write up on the different BBs;

    http://blog.treefortbikes.com/index.php/posts/1473
    Mythical Creatures Touched Me in my Bathing Suit Area.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •