{"id":9188,"date":"2021-01-28T09:01:12","date_gmt":"2021-01-28T09:01:12","guid":{"rendered":"https:\/\/www.firstcomponents.com\/?p=9188"},"modified":"2026-06-22T04:52:15","modified_gmt":"2026-06-22T04:52:15","slug":"bike-bottom-bracket","status":"publish","type":"post","link":"https:\/\/www.firstcomponents.com\/de\/bike-bottom-bracket\/","title":{"rendered":"The Bike Bottom Bracket Ultimate Guide (Quick Reference)"},"content":{"rendered":"\n

A bike\u2019s bottom bracket\u2014or \u201cBB\u201d\u2014together with the rear sprocket and chain constitutes the drive train.<\/p>\n\n\n\n

This article describes the most common BB types, many of which we have covered in detail in individual posts on FIRST\u2019s blog.<\/p>\n\n\n\n

Skim through the headings for an overview, then skip to the section that interests you.<\/p>\n\n\n\n

CONTENTS<\/strong><\/p>\n\n\n\n

THREADED BIKE BOTTOM BRACKETS<\/strong><\/a>
Bsa BBs<\/a>
Square Taper<\/a>
Cartridges<\/a>
Outboard Threaded<\/a>
Bmx<\/a>
Eccentric<\/a>
T47<\/a>
Sram Dub<\/a>
PRESS FIT<\/a><\/strong>
BB30<\/a>
BB86\/92<\/a>
Pf30<\/a>
ADAPTERS<\/a><\/strong>
OTHER STANDARDS<\/a><\/strong>
<\/p>\n\n\n\n

THREE CATEGORIES<\/strong><\/h2>\n\n\n\n

<\/p>\n\n\n\n

Bike bottom brackets are divided into threaded<\/strong> bottom brackets, press fit<\/strong><\/a> <\/a>models<\/a>, and adapters\/converters<\/strong>.<\/p>\n\n\n\n

Cheaper bikes are usually fitted with threaded BBs; more pricey bikes\u2014especially high end \u2018racing\u2019 bikes\u2014use press fit.<\/p>\n\n\n\n

Adapters transform press fit BBs to threaded or threaded to press fit, often to fix a malfunction or to enable the fitting of a specific crank: using an adapter avoids having to buy a new bike or at least a new frame.<\/p>\n\n\n\n

THREADED BIKE BOTTOM BRACKETS<\/strong><\/h2>\n\n\n\n

<\/p>\n\n\n\n

The type of bike bottom bracket you\u2019ll find on a low to mid-end model has threaded cups which match a corresponding threaded bottom bracket shell. <\/p>\n\n\n\n

The cups contain loose, caged, or sealed bearings within which a spindle, which carries the cranks, rotates.<\/p>\n\n\n\n

NOTE<\/strong>: it\u2019s a spindle<\/em> and not an axle<\/em>, since axles do not rotate but remain fixed as bearings rotate around them.<\/p>\n\n\n\n

BSA BB<\/strong><\/h3>\n\n\n\n

<\/p>\n\n\n\n

\u201cBSA<\/a>\u201d is the all-inclusive term often used to refer to threaded bottom brackets as a group. <\/p>\n\n\n\n

\u201cEnglish\u201d threaded is also a common way of referring to the group, and, technically more accurate.<\/p>\n\n\n\n

\u201cBSA\u201d is short for Birmingham Small Arms, a British company whose core business was manufacturing light weapons.<\/p>\n\n\n\n

BSA moved into the bike business during the1880s as bicycles and cycling began to become popular in the lead up to the 1890s bicycle boom.<\/p>\n\n\n\n

The company continued to make bicycle components well into the 20th century, so the term \u201cBSA\u201d stuck.<\/p>\n\n\n\n

The specification is 1.37\u201d diameter with 24 threads per inch.<\/p>\n\n\n\n

Square Taper BB<\/strong><\/h3>\n\n\n\n
\"\"\/<\/figure>\n\n\n\n

The square taper<\/a> design is the bike bottom bracket that came to dominate the BSA\/English threaded category, which it still does today. <\/p>\n\n\n\n

The four angled faces accommodate a crank with a matching aperture, squared and angled in the opposite direction, with one bolt holding it in position on the spindle.<\/p>\n\n\n\n

\"Cottered
Cottered spindle with cage-mounted ball bearings<\/figcaption><\/figure>\n\n\n\n

Cotter pins were a transitional design to the modern square taper.<\/p>\n\n\n\n

A cup and cone contained the bearings with the crank holding tight to the spindle, so long as the cotter pin bolt was kept tight.<\/p>\n\n\n\n

The beauty with this simple and functional bike bottom bracket was the only tool you needed was the right sized open-ended or ring wrench, although cotter pins could get stuck after decades (!) in position requiring extra ingenuity to remove them.<\/p>\n\n\n\n

After that, a screwdriver and hammer will loosen the lockring\u2014out with the cottered crank.<\/p>\n\n\n\n

\"\"\/<\/figure>\n\n\n\n

You could opt for a cup and cone bearing setup with a square taper spindle.<\/p>\n\n\n\n

\"Icetool
Icetool splined crank extractor<\/figcaption><\/figure>\n\n\n\n

The beauty of this design is that bolts replace the cotter pins, although the added complication is the crank extractor tool that you now require to remove the cranks.<\/p>\n\n\n\n

The complete process is detailed in the video.<\/p>\n\n\n\n