At the 2011 Interbike show, Calvin Jones of Park Tool sighed as he described the proliferation of new bottom-bracket dimensions. I've covered all the ones here which I can find, and listed them in order of bottom-bracket shell internal bearing seat diameter so as to highlight compatibilities. Some are obscure or no longer in use. Adapters for some -- ranging from the venerable Ashtabula system to new high-end systems -- allow use with a variety of spindles. Phil Wood makes adapters to fit most press-fit bottom brackets: "[i]f you have a press fit bottom bracket (Merlin, Klein, Fisher, Ritchey, Fat Chance) and need replacement parts, we have spindles and bearings that will work" -- see Phil Wood FAQ page on bottom brackets. Wheels Manufacturing makes a number of adapters between these systems, and FSA makes some. Also see compatibility information in the table below . -- John Allen.
|Standard:||Threading or press fit||Adjustable
|Merlin||30 mm pressed||68 mm|
|Thompson/Thun||30, 33, 35, 38, 40, 45 mm pressed||left (cone and locknut)||right (cone and locknut)||65, 68,70 mm||2-piece or 3-piece crank. Cup and cone bearings. No shoulder inside shell; loose tolerances.|
|Mavic/Stronglight||1.375" (or 35 mm) beveled||65-73 mm||Bottom bracket cartridge clamps into a conventional BB shell once the ends have been faced with a 45-degree taper. Can work with English, ISO, French or Raleigh. Italian?|
|Velo Orange threadless||1.375" (or 35 mm), threaded or unthreaded w/o shoulders||68 mm||Clamps into bottom-bracket shell using expanding sleeves. but not Italian threaded BB shell unless possibly with a steel shim, 0.20"/0.5mm thick. 73mm shell may be too long but could be faced. 76mm Raleigh shell is definitely too long.|
|Fat Chance/Gary Fisher||35 mm pressed||68 or 73 mm||Circlips on grooves in axle outboard of bearings|
|Klein||35 mm pressed||68 mm||Like Fat Chance/Gary Fisher but no axle circlips|
|Ritchey||35 mm pressed||68 mm||Same bearing as Fat Chance/Gary Fisher|
|Shimano Hollowtech II, FSA MegaExo, RaceFace X-type||37 mm pressed or British/ISO threaded||ISO right||ISO left||90 mm, 95 mm including cups||External cups for cartridge bearings fit British/ISO threaded bottom brackets or unthreaded shell. 24 mm spindle, spacer to use 6805 bearings with 25mm I.D.. Bottom bracket shell must be faced so cups are parallel.|
|BB90/BB95||37 mm||90 mm, 95 mm||Used on Trek Madone carbon frames. 24 mm spindle.|
|Spanish||37 mm press fit||19, 20, 22 mm spindle|
|Mid||41 mm press fit||19, 20, 22 mm spindle|
|BB83/BB86, BB92||41 mm press fit||86, 92 mm||19 mm or 24 mm spindle|
|Thun-BB30||42 mm press fit||68, 73 mm||Plastic cups retained by shoulders, like PF30. Can fit BB30 bore but not vice versa.|
|BB30, Cannondale System Integration||42 mm press fit||68, 73 mm||Adapters allow use with various 30 mm spindles.|
|BBRight Direct Fit||42 mm press fit||79 mm||Asymmetrical: 34mm center to right. 30 mm spindles|
|Swedish OPC||45 mm||external||external||?|
|Specialized OSBB Aluminum||42 mm||68mm||See compatibility guide. Usable with several BB30 spindles with Wheels Mfg. adapters|
|Roadmaster child's||43 mm||65 mm|
|Specialized OSBB Carbon||46 mm||61 mm||See compatibility guide. Adapters increase shell width to 68 mm. Usable with several BB30 spindles with Wheels Mfg. adapters|
|Pressfit 30 (PF30)||46mm slip fit||68, 73 mm||30 mm OD spindle; plastic retainer for cartridges.|
|BBright Press Fit||46 mm||79 mm||Asymmetrical: 34mm center to right. Adapters allow use of various spindles.|
|BB386EVO||46 mm press fit||86.5 mm||Like PF30 but wider and with press-fit bearings. See info from FSA Web site. (archived).|
|ISIS Megatech||48 mm pressed||68 mm|
|FSA Megatech||50 mm pressed||68, 73, 83 mm|
|Phil Wood American Isis (comments)||50 mm||right||left||1.5 mm thread pitch.|
51.3 mm (2.02") i.d.
|left (cone and locknut)||right (cone and locknut)||
68 mm (2.68") wide
| Older U.S. bikes, BMX, Juvenile bikes,
Department store bikes.
24 tpi cranks use #66 retainers, with 10 5/16" balls.
28 tpi cranks use #64 retainers, with 9 5/16" balls.
Note: Some higher quality(mostly BMX) bikes used Tange 24 tpi bottom brackets with #64 retainers.
|Eccentric||54 mm||68 mm||For tandems and single-sprocket drive with vertical dropouts or belt drive. May be split with pinch bolts, or have setscrews. Shell diameter not critical, internal dimensions for bottom bracket may vary. Also see Gary Fisher Eccentric below.|
|Gary Fisher Eccentric||57 mm||73 mm||Also see Eccentric above.|
Last Updated: by John Allen