What are the different types of bottom brackets?

Asked by: Chris Barnett

There are two main types of bottom bracket design, one with a threaded shell which the bearings screw into, or a press-fit design which the bearings press into the shell.

How do I know which bottom bracket I need?

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.

How do I know if my bottom bracket is Italian or English?

The key difference is in how the two thread into the bottom bracket shell. Like pedals, one side of a BSA standard bottom bracket shell is reverse (left) threaded, while both sides of an Italian standard bottom bracket shell are regularly (right) threaded.

Are all bottom bracket threads the same?

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).

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.

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).

Why is bottom bracket creaking?

Most of the time, the true cause is a loose chainring bolt—tighten them up and that’ll quiet most creaks. After you check the chainring bolts and if you still hear the noise, look at your pedals, crank bolts, seatpost, and seat. By checking these first, you’ll save an hour of digging into your bottom bracket.

What does BSA stand for bottom bracket?

The term BSA stands for Birmingham Small Arms, a British company that produced bicycles, cars and other durable goods. The term BSC stands for British Standard Cycle, which adopted the same standard. BSC is sometimes shortened to BC.

How long do bottom brackets last?

As for a bottom bracket, on the low end, maybe 5000 miles. The basic Shimano one most people use (UN51/55/similar) can reasonably expect 10k+ miles. But sometimes you get unlucky and get a bottom bracket that lasts maybe 500 miles.

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.

What is most common bottom bracket?

BSA, or English threaded bottom bracket, is the most common threaded standard in use today. It uses a 68mm wide shell for road bikes, 73mm on mountain bikes, with a 34.8mm diameter shell. A few bike brands use an Italian threaded bottom bracket but these are rare.

Does changing bottom bracket make a difference?

(Click here to read BikeRadar’s complete guide to bottom brackets.) According to Friction Facts’ latest report: “No statistically significant difference exists showing a general advantage or disadvantage of a standard type under similar loading conditions.

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 is a hollowtech bottom bracket?

HOLLOWTECH technology is an ultra-lightweight hollow crankarm created by SHIMANO with the company’s own proprietary forging technology that also maintains rigidity.

What is the difference between BB92 and BB86?

BB86 vs BB92? No difference. They are one and the same bottom bracket. Well, BB86 refers to road bikes with their 68mm BB shell; BB92 refers to mountain bikes with their 73mm BB shells.

What is the difference between BB386 and BB386 Evo?

What Type of Bottom Bracket do I Have?

How do you tell if a cranks will fit my bike?

Crank length is measured from the centre of the bottom bracket axle to the centre of the pedal axle. If you’re not sure what length the cranks on your bike are, the quickest way of finding out is typically to just look at the backside of your cranks, just below the pedal axle.

How do I know what crankset I have?

Print. Shimano cranks are all identified with model information above or surrounding the area on the backside of the pedal threads. For example; FC-6700/6750 = Shimano Ultegra. The crank length is often located in the same area, which is helpful to note before placing an order.

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 is a 68 73 bottom bracket?

The 68mm and 73mm dimension measure the width of the bottom bracket on the frame of the bike with no BB installed, simply the width of the shell. Most road bikes that use a threaded bottom bracket measure 68mm wide and most cross country/trail mountain bikes measure 73mm.

What spindle length do I need?

The best way to find out which spindle length you need is by looking up the specs. (The alternative is trial and error…) Spindle length and the resulting chainline have some leeway. If you are within 2-3 mm of the “correct” 43.5 mm or 45 mm, you are doing quite well.

What is the difference between bb386 and bb386 Evo?

A standard 68mm BB shell width allows a down tube or seat tube diameter of around 63mm maximum. The BB386EVO system allows a much more generous amount of area, up to around 83mm.