The Ultimate Guide to Bicycle Bottom Bracket Standards (BB)

by Biju K on May 05, 2021

The plethora of options available for Bottom Brackets (BB) in the cycling world can be quite confusing, even for people with good cycling knowledge. The standards are ever changing and overlapping. Here's your ultimate guide on BB!

Crankset and Bottom Bracket

Here's a short note to distinguish them:

Threaded

  • English (BSA) (1.37″ x 24) / (34.8mm x 24)
  • ISIS Overdrive, 
  • Italian
  • French
  • Swiss 
  •  T47 (47mm x 1mm)

PressFit

  • PF41 (ALSO KNOWN AS BB86, BB89.5, BB92, BB107, BB132, SHIMANO® PRESS-FIT, PF24)
  • PF42 (ALSO KNOWN AS BB30, BB30A, BB30AI, BBRIGHT™ DIRECT FIT)
  • PF46 (ALSO KNOWN AS PF30, PF30A, PF30AI, BB386EVO, OSBB, BBRIGHT™ PRESS FIT)
  • BB90 AND BB95 Trek® - shell is not a straight bore but has an internal bearing retainer built into the shell, similar to an integrated headset. Bearing outside diameters are 37mm.
  • SPANISH PRESS FIT BMX standard. The frame bore is nominally 37mm. Spindle ODs may be either 19mm or 22mm
  • MID PRESS FIT BMX standard. It uses a 41.2mm (1-5/8″) diameter cartridge bearing. Like the Spanish standard, the bearing is pressed directly into the frame.
  • AMERICAN (ASHTABULA) 51.5mm cup pressed into the frame. It is seen on older Schwinn® bicycles, some BMX bicycles. one-piece crankset

Less popular Threaded 

  • ISIS OVERDRIVE 48mm x 1.5mm. The drive side is a left hand thread and the non-drive side is a right hand thread.
  • ITALIAN STANDARD The Italian Standard uses a threading of 36mm x 24 threads per inch. Both sides of the bottom bracket are right hand threaded. distinguished by a 35mm inside diameter.

Threaded BSA Bottom Bracket - HollowTech II

Deep dive into Bottom Bracket Standards

Finding the correct bottom bracket for your frame can be challenging. To accurately determine the bottom bracket standard in your frame, it is best that you remove your crankset, and any installed bottom bracket cups or bearings. Then measure both the inner diameter and width of your frame's bottom bracket shell.

The chart below lists most of the current bottom bracket standards found on today's frames. Once you determine your bottom bracket standard, you then need to Identify Your Crankset.

BB Standard

Frame BB Shell
Inner Diameter

Common Shell Width

Frame BB
Shell Threaded?

Also Known As

Notes

Wheels Mfg Bottom Brackets

BSA Threaded
  • 1.37 in x 24 TPI
  • 33.6mm - 33.9mm
  • 68mm (road)
  • 73mm (mountain)
  • 83mm (Downhill)
  • 100MM (Fat Bike)
  • Yes
  • Standard Threaded
  • English Threaded

Most common threaded BB shell system.

  • 1.37 in x 24 TPI
  • Left hand thread on drive-side
  • Right hand thread on non-drive
TREK BB90
  • 37mm
  • 90.5mm
  • No
  Trek direct-fit system. Bearings are pressed directly into frame.
TREK BB95
  • 37mm
  • 95.5
  • No
  Trek direct-fit system. Bearings are pressed directly into frame.
BB86 / BB92
  • 41mm
  • 86.5mm
  • 90mm
  • 91.5mm
  • 104.5mm
  • 107mm (DH / Mountain)
  • 121mm (Fat Bike)
  • 132mm (Fat Bike)
  • No
  • PF24 (Chris King)
  • PF41 (Hope)
  • PF86
  • PF92 (Trek)
  • BB107/PF107
  • BB121
  • PF121 (Trek)
  • BB132

Designed to be used with 24mm spindle diameter cranks (Shimano HollowTech II), hence the PF24 designation. But, can also use GXP cranks in these.

Some brands call this PF41, describing the frame shell diameter instead of the crank spindle diameter.

Removable bottom bracket cups.

BB30
  • 42mm
  • 68mm (road)
  • 73mm (mountain)
  • 84.5mm (Specialized MTB Alloy OSBB)
  • 83mm (Cannondale MTB)
  • 120mm (Cannondale Fat Bikes)
  • No
  •  Specialized Alloy OSBB

6806 bearings are pressed directly into the frame.

May use removable c-clips as bearing stops, or the bottom bracket shell may have molded or machined bearing stops.

Symetrical shell

BBRight (Direct Fit)
  • 42mm
  • 79mm
  • No
 

Cervelo R5ca Frames only. BB shell is 11mm wider on the non-drive side.

6806 bearings are pressed directly into the frame.

Specialized OSBB Alloy
  • 42mm
  • 68mm (Road)
  • 84.5mm (Mountain)
  • No
 

Same as BB30.

6806 bearings are pressed directly into the frame.

Cannondale BB30a
  • 42mm
  • 73mm
  • 83mm (Cannondale BB30A-83)
  • No
 

Asymetrical BB shell is +5mm wider on the non-drive side (BB30A). For the BB30A-83 frames, the BB shell is 5mm wider on the drive side and +10mm wider on the non-drive side.

6806 bearings are pressed directly into the frame.

PF30
  • 46mm
  • 61mm (Specialized OSBB/FACT)
  • 68mm (Road)
  • 73mm (Mountain)
  • 83mm (Downhill)
  • 100MM (Fat Bike)
  • No
  • PressFit-30

Removable bottom bracket cups.

BBRight (Press Fit)
  • 46mm
  • 79mm
  • No
 

Cervelo Frames except R5ca. Also used by 3T.

Removable BB cups.

BB shell is 11mm wider on the non-drive side.

Specialized OSBB Carbon (Road)
  • 46mm
  • 61mm (Road)
  • No
 

Specialized carbon road frames with 61mm wide shells for use with Specialized FACT cranks.

Removable BB cups.

Cannondale PF30a
  • 46mm
  • 73mm
  • 83mm (Cannondale PF30A-83)
  • No
 

Asymetrical BB shell is +5mm wider on the non-drive side (PF30A). For the PF30A-83 frames, the BB shell is 5mm wider on the drive side and +10mm wider on the non-drive side.

Removable BB cups.

Cannondale Asymmetric Integration (Ai)
  • 46mm
  • 83mm
  •  No
 

Cannondale Asymmetric Integration (Ai) found on Scalpel-Si and F-Si System frames. BB shell is 83mm wide, but symetrical

Removable BB cups.

T47
  • M47 x 1 Threaded
  • approx. 46mm ID
  • 68mm
  • 73mm
  • 83mm
  • 100mm
  • Yes
  • Threadfit 30i

Frame's bottom bracket shell is threaded with M47 x 1 threads.

  • Left hand threads on the drive-side
  • Right hand threads on the non-drive.
386EVO*
  • 46mm
  • 86mm
  • No
 

* Essentially a PF30 with 86.5mm wide shell.

392EVO*
  • 46mm
  • 92mm
  • No
 

* Essentially a PF30 with 92mm wide shell.

Colnago ThreadFit82.5
  • 41mm
  • 86.5mm
  • Yes*
 

* Colnago standard with a threaded BB shell. Aluminum cups are threaded into the frame that result in the BB86 standard (41mm ID x 86.5mm width).

Wheels Mfg does not make the threaded cups for these frames. Visit excelsports.com for cups
Look BB95
  • 65mm
  • 90mm
  • No
 

Unique to Look frames. Requires bearings and hardware from Look

  • Wheels Mfg does not offer any compatible bottom brackets for Italian threaded frames.
Wilier BB94
  • 37mm
  • 93mm
  • No
  • BB93

Unique to Wilier. Bearings press directly into the frame. Similar to Trek BB90

Truvativ ISIS Overdrive
  • M48 x 1.5 Threaded
  • 68mm - 100mm
  • Yes
 

Little used threaded BB shell standard. Usually found on Cyclops indoor bikes. *NOT COMPATIBLE WITH T47*

  • Wheels Mfg does not offer any compatible bottom brackets for Italian threaded frames.
Italian
  • 36mm X 24tpi
  • 70mm
  • Yes
   
  • Wheels Mfg does not offer any compatible bottom brackets for Italian threaded frames.

 

Notes:

To accurately identify your frame's BB shell, always measure the ID and width. Or, have a professional bike mechanic do the work for you.

  • Press-Fit refers to aluminum or plastic bottom bracket cups, which are pressed into the frame. The bearings are then pressed into the cups.
  • Direct-Fit refers to individual bearings pressed directly into the frame with no removable BB cups.

 

 

Here's a bit more info on popular PressFit types:

Trek BB90/95 Technical Info

The BB90/95 standard is currently used by Trek. Two sealed bearings are pressed directly into the frame's bottom bracket shell. A step is moulded in to the frame for the bearings to seat against. Trek BB90/95 frames do not have bearing retainer clips. Compatible with 24mm or 24/22mm spindle cranks only.

  • Shell width: 90.5mm (road) or 95.5mm (mountain)
  • Shell ID: 37mm
  • Uses two sealed bearings (37mm OD) which are pressed into the frame and stop against a raised step built into the frame's bottom bracket shell.
  • No snap rings are used.

BB90/95 Exploded View

BB86/92 Technical Info

The BB86 bottom bracket shell is 86.5mm wide and the BB92 shell is 91.5mm wide. Both have an inside diameter of 41mm. Originally designed to use 24mm or 22/24mm diameter crank spindles, some frames can run 29mm and 30mm diameter crank spindles with direct-fit bearings. BB86/92 bottom brackets consist of bearings pressed into cups, which are then pressed into the frame. The main dimension with this standard is the inside diameter of the BB shell: 41mm. There are other standards that also have a 41mm ID: PF24, PF41, PF107, PF121, PF132
  • Common Shell Widths: 86.5mm (road) or 91.5mm (mountain)
  • Also used in shell widths: 89.5mm, 104.5mm, 107mm, 121mm, 132mm
  • Shell ID: 41mm
  • Bearings are pressed into cups which are pressed into the frame
  • Shell may have a stepped design but there are no snap ring grooves

BB86/92 Bottom Brackets

 

BB30 Technical Info

The BB30 bottom bracket shell is typically 68mm (road) or 73mm (mtb) wide with an inside diameter of 42mm. Originally the BB30 system was designed to use 30mm diameter crank spindles. However, frame's with BB30 shells can be used many other sized crank spindles. A BB30 shell itself is not threaded, instead the bearings press directly into the frame, also known as a direct-fit bearing system. BB30 shells often use bearing retaining clips behind the bearings to set the proper depth of the bearings in the frame. A few frames may use a molded or machined step in the shell to locate the bearing stop. The BB30 system uses thin spacers and/or a wave washer between the bearings and the crank arms to take up any slack and micro-adjust the chainline of the crank.

  • Shell width: 68mm (road) or 73mm (mountain)
  • Shell inner diameter (ID): 42mm
  • Bearings (42mm OD) pressed directly in frame.

 

BB30 Bottom Brackets

 

Specialized Alloy OSBB Technical Info

Specialized Alloy OSBB frames adopt the BB30 bottom bracket system, using a bottom bracket shell with a 42mm inner diameter. Alloy OSBB road frames may have a machined aluminum shell, or may use aluminum inserts permanently bonded into a carbon shell. Both configurations have a BB width of 68mm, and are essentially BB30 systems with the bearings pressed directly into the frame or aluminum inserts.

Alloy OSBB mountain frames have a 42mm inside diameter BB shell with a 84.5mm width. This is much wider than a normal BB30 system. If looking to run 22mm/24mm (GXP) or 24.00mm cranksets in these frames, we recommend our 386EVO adapters.

  • Shell width: 68mm (Road), 84.5mm (Mountain)
  • Shell inner diameter (ID): 42mm
  • Bearings pressed directly in frame or permanently installed aluminum inserts

BB30 Bottom Brackets

PF30 Technical Info

PressFit-30 (PF30) bottom brackets are a separate component pressed directly into the frame. The PF30 bottom bracket shell is typically 68mm (road) or 73mm (mtb) wide with an inside diameter of 46mm. The bearings are pressed into cups and the cups then pressed into the frame. Originally designed for 30mm spindle cranks, there are many available bottom brackets for 29mm SRAM DUB cranks, 24mm (Shimano, FSA, etc.) cranks or 22/24mm (GXP, SRAM, etc.) cranks.

  • Frame shell width: 68mm (road), 73mm (mountain), 83mm (downhill)
  • Frame shell ID: 46mm
  • Bearings pressed into cups

PF30 Bottom Brackets

 

Specialized Carbon OSBB Technical Info

Specialized OSBB is the term used by Specialized on many of their frames. Unfortunately, this doesn't tell us much about the specific dimensions of the BB shell in an OSBB frame. Most Specialized Carbon OSBB mountain frames are 73mm wide and 46mm inside diameter. This is your normal PF30 BB shell. You will use a PF30 bottom bracket that has bearings pressed into the BB cups and the cups in turn press into the frame. The exception being the Demo frames which are 83mm wide and 46mm ID.

Beginning 2011, OSBB Carbon road frames were made with a 46mm inner diameter shell and a 61mm wide shell. OSBB Carbon road frames with a 61mm wide shell were designed to work with Specialized FACT cranks. These cranks have shorter spindles, and do not fit bikes with 68mm or wider shells. If using these cranks with a Wheels Mfg PF30 bottom bracket on a 61mm wide shell, you do not need to use any additional cup spacers between the BB cups and the frame.

If you are using cranks other than the short-spindle FACT cranks on a Carbon OSBB road frame (61mm wide BB shell), you should add 3.5mm of cups spacers to each side between the cup and the frame. This effectively widens the shell to 68mm, which is what most cranks spindle lengths are based on.

After a few years, Specialized changed their OSBB road frames by permanently bonding aluminum cups into the 61mm wide shell. The bearings are pressed into these aluminum cups. This made the frame essentially a BB30 frame (68mm x 42mm).

  • Shell width: 61mm (Road), 73mm (Mountain)
  • Shell ID: 46mm
  • The frame's bottom bracket shell will have a smooth bore (no snap ring grooves)

Specialized Carbon OSBB Exploded View

 

If you are looking for buying a bottom bracket online in India, Cycling Boutique is the place to approach for getting best reliable technical assistance on bicycle maintenance and repair. Cycling Boutique Experience Center, Bengaluru is the most technical skilled bicycle repair shop (Bike Service Shop) in India to get your favourite international bicycles to get repaired - bet it a Trek, Giant, Scott, Bergamont, Specialized, Marine, Sulry, Cannondale, Bianchi, Schwinn, Fuji, Focus, Look, Colnago, Cervelo, Canyon, De Rosa, Cipollini,  - we service them in the finest ways with the finest tools and technicians in India.

 

*Courtesy: Our channel partners - Wheels Manufacturing USA, Parktool USA and CEMA bearings.

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