Nederlands | English | Deutsch

Project Sports

Questions and answers about sports

Can BSA 68/73 bottom bracket be used in place of fat bike BSA 100 mm

5 min read

Asked by: Lee Ferguson

What is a BSA 68 bottom bracket?

The short answer to your question is that when you see BSA in terms of a bottom bracket, it refers to a 68 or 73mm shell with 1.370/1.375″ x 24 TPI threads and a left hand thread on the drive side cup.

How do I know which bottom bracket is compatible?

To find out the size of bottom bracket needed, measure the inside of the bottom bracket shell in your frame, it will be 73mm, 70mm or 68mm. Some older frames may have Italian threaded bottom brackets, instead of the more modern English.

What size is a BSA bottom bracket?

Bottom Bracket Standards

BB Standard Frame BB Shell Inner Diameter Common Shell Width
BSA Threaded 1.37 in x 24 TPI 33.6mm – 33.9mm 68mm (road) 73mm (mountain) 83mm (Downhill) 100MM (Fat Bike)
TREK BB90 37mm 90.5mm
TREK BB95 37mm 95.5
BB86 / BB92 41mm 86.5mm 90mm 91.5mm 104.5mm 107mm (DH / Mountain) 121mm (Fat Bike) 132mm (Fat Bike)

How wide is a fat bike bottom bracket?

Fat Bike BB Tech Links



Wheels Mfg Fat Bike PF30 bottom brackets are for use in bottom bracket shells with a 46mm ID and 100mm wide. Our bottom bracket consists of two machined cups with sealed bearings pressed in.

Is BB92 the same as PF92?

The frame’s bottom bracket shell inner diameter is 37mm. A bearing with an OD of 37mm is pressed directly into the frame. Trek is moving away from the BB90/95 system to what they call PF92, which is the same as a BB92 (41mm ID shell and 92mm width).

Are all bike bottom brackets the same size?

There are 4 widths available with BSA bottom brackets; 68mm, 73mm, 83mm or 100mm. This bottom bracket clearly shows you on the outside what bearings have been fitted to the bike. For road bikes, a BSA bottom bracket is always 68 mm wide. Other sizes, and particularly the 73 mm width, is commonplace with mountain bikes.

Can I put any bottom bracket on my bike?

To a certain extent which bottom bracket you end up buying is up to what kind of frame you have. Certain frame materials and drivetrain options only support one type of Bottom Bracket. There are two main types of bicycle bottom brackets in today’s market, namely, threaded and press-fit BB’s.

Do all cranksets fit all bikes?

Bicycle cranksets come in different sizes with different fittings for the types of bikes in the market. Therefore, as we had discussed earlier, cranksets range from 16mmm to 190mm. Also, some bikes have wider bottom bracket shells, and this calls for a specific axle. Therefore, all cranksets don’t fit all bikes.

How do I know if my crankset is compatible?

In most cases three-and two-piece cranksets are compatible with the same bottom brackets so long as the axle is the same diameter. They are commonly used in conjunction with the mid-style bottom bracket standard. One-piece: This is where the axle and crank arms are a single piece of steel.

Are all BSA bottom brackets the same?

The size of the shell is also different, with BSA bottom brackets using a 1.375” (34.92mm) diameter shell and Italian BB’s using a 36mm diameter shell. The width of the bottom bracket shell is also different; BSA bottom brackets are usually 68mm or 73mm wide, while Italian threaded bottom brackets come in at 70mm wide.

What do numbers on bottom bracket mean?

The numbers ranging from 86 to 132 refer to the nominal width of the shell in millimeters, which is not related to the press fit of the bearings. These bottom brackets will vary in the width of the dust sleeve used for that different widths.

What is the difference between BB30 and BSA?

BSA is English standard and have screw thread inside the hole ,usually use in shimano,while BB30 is Italian standard and don’t have screw thread, usually use in CP.

Do all cranks fit all bottom brackets?

In general terms, most cranksets can be fitted to a variety of bottom bracket shells, though much of this compatibility depends upon the availability of suitable hardware (see next section). Any incompatibilities that do arise are often related to the length and/or diameter of the crank axle.

Does bottom bracket spindle length matter?

The critical thing is your spindle length: as long as you can set up the correct chainline you will be good to go. But, again, best never to mix standards if you can at all avoid it. If you are looking to replace a cottered crank setup with a square taper setup, then look no further than a cartridge bottom bracket.

Are Shimano bottom brackets interchangeable?

All Shimano Hollow-Tech II road bottom bracket cups are interchangeable, that is they all have the same bottom bracket shell threads, fit in same shell width, have the same axle diameter and overall width.

What is the difference between BB30 and BSA?

BSA is English standard and have screw thread inside the hole ,usually use in shimano,while BB30 is Italian standard and don’t have screw thread, usually use in CP.

What does BSA stand for MTB?

BSA (Birmingham Small Arms) have not really made a bottom bracket since 1957 when the bicycle division was sold to Raleigh. They continued making bikes under the name for a few years before phasing it out.

What does BSA stand for in bikes?

Birmingham Small Arms Company Ltd

BSA First Motorcycle



Standing for Birmingham Small Arms Company Ltd, BSA was founded in 1861, for the production of firearms.

What is BSA thread?

The frame’s bottom bracket has threads cut in to the shell. Typically threads are BSA (1.37″ x 24tpi), Italian (36 x 24tpi) or French (35mm x 1). Most of the current bottom brackets available from Shimano, SRAM, FSA and Campagnolo use external bearing cups.

Will a 68mm bottom bracket fit a 70mm shell?

No. There are two different tapers, several different threads and several different lengths. Different bottom bracket shell widths.

Are bottom brackets interchangeable?

Threaded bottom brackets shells have been made over time in various thread standards that are not interchangeable. The common threaded bottom bracket uses cups or adapters with the thread specification of 1.37″ x 24 threads per inch (approximately 34.8mm diameter).