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Sheldon Brown's Threaded Bicycle Bottom Bracket Crib Sheet

(See also Unthreaded Bottom-Bracket Dimensions Cribsheet and my Bottom Bracket Size Article)

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Standard: Threading or press fit Adjustable
(left) cup/cone
direction
Fixed
(right) cup/cone
direction
Shell
Width
Applications/Notes
British
I.S.O.
1.370" X 24 tpi
1.375" X 24 tpi
right left Standard 68 mm
O.S. 73 mm
The overwhelming majority of bicycles in current production. British and I.S.O. are interchangeable.
Shimano Hollowtech II, FSA MegaExo, RaceFace X-type ISO right 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.
Campagnolo Ultra-torque Italian or ISO       Spindle diameter 25mm.
French 35 mm X 1mm (25.4 tpi) right right
(wrong!)
68 mm Obsolete, used on older French bicycles.
Prone to problems due to the right threaded fixed cup, which tends to unscrew itself in use.
ISIS Overdrive I 48 x 1.5 mm right right
(wrong!)
68mm
100 mm
 
ISIS Overdrive II 48 x 1.5 mm right left 68mm
100 mm
New proposed standard oversized system.
Italian 36 mm X 24 tpi right right
(wrong!)
70 mm Italian and some high-end French bicycles. Prone to problems due to the right threaded fixed cup, which tends to unscrew itself in use.
Raleigh 1 3/8" X 26 tpi right left 71 mm
76 mm
Older British-made Raleighs, especially 3 speeds.
Swiss 35 mm X 1mm (25.4 tpi) right left 68 mm Same thread as French, but fixed cup is left- threaded for reliability.

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What happens if you try to mix different sizes:

Bottom Bracket
Shell Threading
(Below)
BritishI.S.O.
1.37/1.375" x 24 tpi CUPS R-L
(34.8/34.9 x 1.06 mm)
Italian
36 mm X 24 tpi CUPS R-R
(1.417" x 1.06 mm)
French
35 mm X 1mm CUPS R-R
(1.378 x 25.4 tpi)
Swiss
35 mm X 1mm CUPS R-L
(1.378 x 25.4 tpi)
Raleigh
1 3/8" X 26 tpi CUPS R-L
(34.9 x 1.06 mm)
British/I.S.O.
1.37/1.375" x 24 tpi
(34.8/34.9 x 1.06 mm)
Made to Fit 36 mm Cup diameter is too large, thread won't even start. Cup diameter is slightly too large, usually won't start.
Right (fixed) up threaded in the opposite direction.
Cup diameter is slightly too large, usually won't start. Diameter matches, but thread pitch does not.

Will bind after only a few threads are engaged.

Italian
36 mm X 24 tpi
(1.417" x 1.06 mm)
British/I.S.O. cups fall through Made to Fit Italian shells are larger diameter, all other size cups fall right through, threads will not engage.
French
35 mm X 1mm
(1.378 x 25.4 tpi)
35 mm = 1.378". Shell is slightly larger, thread pitch slightly finer.
Left side may seem to fit, but will be loose.
36 mm Cup diameter is too large, thread won't even start. Made to Fit Left (adjustable) side is interchangeable.
Right (fixed) side is threaded in the opposite direction, won't fit.
35 mm = 1.378". Shell is slightly larger, thread pitch slightly coarser.
Left side may seem to fit, but will be loose.
Swiss
35 mm X 1mm R
(1.378 x 25.4 tpi)
35 mm = 1.378". Shell is slightly larger, thread pitch slightly finer. May seem to fit, but will be loose. 36 mm Cup diameter is too large, thread won't even start. Left (adjustable) side is interchangeable.
Right (fixed) side is threaded in the opposite direction, won't fit.
Made to Fit 35 mm = 1.378". Shell is slightly larger, thread pitch slightly coarser.
May seem to fit, but will be loose.
Raleigh
1 3/8" X 26 tpi
(34.9 x 1.06 mm)
Diameter matches, but thread pitch does not.

Will bind after only a few threads are engaged.

36 mm Cup diameter is too large, thread won't even start. Cup diameter is slightly too large, usually won't start.
Right (fixed) up threaded in the opposite direction.
Cup diameter is slightly too large, usually won't start. Made to Fit

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Chainline Dimensions (See also my Chainline Article )

Application Dimension Notes
Road Double 43.5 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 Shimano spec, measured to the middle ring.
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 derailer mechanism farther to the right.
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
Singlespeed MTB 52 mm Wider chainline need for chainstay clearance on MTBs.

This is close to the chainline of the outer ring of a typical MTB triple

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.
Rohloff Speedhub 54 mm
(58 mm w/13 tooth)
Freeride and Downhill 55 mm Newer Freeride and Downhill bikes with 150 mm spacing

More cribsheets: Click here!

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.

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