Sheldon Brown's Unthreaded Bicycle Bottom Bracket Crib Sheet

This file updated by John Allen, April 2014

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 cone direction	Fixed cone direction	Shell Width	Applications/Notes
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
Ashtabula , O.P.C.	51.3 mm (2.02") i.d. (approximate). External threads on crank are 24 tpi (most) 28 tpi (Schwinn, Mongoose)	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.

Standard:

Threading or press fit

Adjustable
cone
direction

Fixed
cone
direction

Shell
Width

Applications/Notes

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

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

Ashtabula , O.P.C.

51.3 mm (2.02") i.d.
(approximate).

External threads
on crank are
24 tpi (most)
28 tpi
(Schwinn,
Mongoose)

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.

Chainline Dimensions (See also my Chainline Article )

Application	Dimension	Notes
Track/Coaster Brake Traditional One-Speed Most internal gear hubs	40.5-42 mm	Older bikes with 110 spacing would be on the smaller end of this range Newer bikes with 120 mm spacing normally use 42 mm
Road Double	43.5 mm	Shimano spec, measured to the midpoint between the rings. with typical 5 mm chainring spacing, this puts the inner at 41 mm, the outer at 46 mm.
Road Triple	45 mm	Shimano spec, measured to the middle ring.
Singlespeed MTB Alternate	47.5 mm	White Industries ENO hubs use this chainline, which lines up with the middle position of a typical MTB triple. It's also fairly close to the outer position of a typical "road" double.
MTB Triple	47.5-50 mm	Shimano spec, measured to the middle ring. 47.5 preferred, but for frames with oversized seat tubes, the longer dimension may be needed, because the fat tube places the front derailer mechanism farther to the right. SRAM standard chainline is 49mm with 142mm OLD and thru axle
Singlespeed and Single-chainwheel MTB, "Boost 148"	52 mm	Wider chainline need for chainstay clearance on newer MTBs, typically with disc brakes and 148 mm OLD spacing This is close to the chainline of the outer ring of a typical MTB triple.
Rohloff Speedhub	54 mm (58 mm w/13 tooth)	Sprockets are proprietary, threaded. All except the 13-tooth may be flipped over to double wear life.
Freeride and Downhill	55 mm	Newer Freeride and Downhill bikes with 150 mm spacing
Tandem	about 60 mm	Tandems with 160 mm spacing
Fatbike	66 mm	Fatbikes with 170 mm spacing
Fatbike	76 mm	Fatbikes with 190 mm spacing -- needed with 4.8" (125 mm) wide tires.

Application

Dimension

Notes

Track/Coaster Brake
Traditional One-Speed
Most internal gear hubs

40.5-42 mm

Older bikes with 110 spacing would be on the smaller end of this range
Newer bikes with 120 mm spacing normally use 42 mm

Road Double

43.5 mm

Shimano spec, measured to the midpoint between the rings.
with typical 5 mm chainring spacing, this puts the inner at 41 mm, the outer at 46 mm.

Road Triple

45 mm

Shimano spec, measured to the middle ring.

Singlespeed MTB
Alternate

47.5 mm

White Industries ENO hubs use this chainline, which lines up with the middle position of a typical MTB triple.
It's also fairly close to the outer position of a typical "road" double.

MTB Triple

47.5-50 mm

Shimano spec, measured to the middle ring.
47.5 preferred, but for frames with oversized seat tubes, the longer dimension may be needed, because the fat tube places the front derailer mechanism farther to the right. SRAM standard chainline is 49mm with 142mm OLD and thru axle

Singlespeed and Single-chainwheel MTB, "Boost 148"

52 mm

Wider chainline need for chainstay clearance on newer MTBs,
typically with disc brakes and 148 mm OLD spacing
This is close to the chainline of the outer ring of a typical MTB triple.

Rohloff Speedhub

54 mm
(58 mm w/13 tooth)

Sprockets are proprietary, threaded. All except the 13-tooth may be flipped over to double wear life.

Freeride and Downhill

55 mm

Newer Freeride and Downhill bikes with 150 mm spacing

Tandem

about 60 mm

Tandems with 160 mm spacing

Fatbike

66 mm

Fatbikes with 170 mm spacing

Fatbike

76 mm

Fatbikes with 190 mm spacing -- needed with 4.8" (125 mm) wide tires.

This page is intended as a quick reference primarily for the benefit of folks in the bicycle business. Feel free to print it out, but please don't reproduce it without proper credit and linkage.