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Sport Factory Blog

Bottom Bracket Guide: Types, Sizes, Torque and Wear

Posted by Matt Russ

Bottom Bracket Guide: Types, Sizes, Torque and Wear

Bicycle bottom bracket mounted in its frame

The bottom bracket is the set of bearings inside your frame’s bottom bracket shell that lets your crankset spin. To buy the right one, you need three things: your frame’s shell type (threaded or press-fit), its shell width, and your crank’s spindle. Match those and the swap is straightforward. Miss one and you get a part that does not fit or a bike that creaks.

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TL;DR

  • The bottom bracket (BB) holds the bearings the crankset rotates on. Frame shell and crank spindle decide which one fits.
  • Sizes are not universal. Threaded shells (BSA, T47) and press-fit shells (BB86/92, BB30, PF30) each come in road and mountain widths.
  • Torque depends on the exact part. Shimano threaded cups call for 35 to 50 Nm, and SRAM DUB BSA units for 50 Nm. Always check the manual.
  • A creak or tick under pedaling load that survives a crank-bolt check often points to the BB. A rough or wobbly spin with the chain off confirms it.
  • Threaded systems are generally easier to install, remove and keep quiet. Press-fit systems can give frame designers more freedom.

Table of Contents

What a bottom bracket does

Your crank arms attach to a spindle, and that spindle has to turn freely inside the frame while taking the full force of every pedal stroke. The bottom bracket is the bearing system that makes this possible. It sits in the cylindrical shell at the junction of the seat tube, down tube and chainstays.

Because every watt you produce passes through it, a bottom bracket that is dirty, loose or worn costs you smoothness and can turn a quiet bike into a noisy one. It is not a part you see, but you feel it.

The bottom bracket does not work alone. The shell in your frame, the crank spindle and the bearings all have to agree on diameter, width and thread (or lack of it). That is why the question “what bottom bracket do I need?” has no single answer.

The two families: threaded and press-fit

Nearly every modern bottom bracket falls into one of two families. The difference is how the bearings are held in the frame.

Threaded bottom brackets

Threaded shells have internal threads cut into the frame. The bottom bracket cups screw into those threads and tighten against the shell. Common standards are BSA (also called English or ISO) and T47. BikeRadar’s guide to bottom bracket standards notes that threaded external-cup systems remain common because they support broad crank compatibility and are generally easier to install and remove than press-fit systems.

If you do your own wrenching, or want a frame that is simple to service for years, threaded is the friendly option.

Press-fit bottom brackets

Press-fit shells have no threads. The bearings, or a cup holding them, are pressed directly into a smooth bore. Common standards include BB86/92, BB30 and PF30. BikeRadar points out that press-fit systems can be more susceptible to creaking, while the broader industry shift toward them was driven by frame design: the BOTTOM-BRACKETS.info overview describes how different frame and bottom bracket standards were developed to cut weight while keeping or improving stiffness, which also produced systems that do not interchange.

Press-fit is not a flaw. It is a different design choice, and a well-prepared press-fit shell with a quality bottom bracket can run quietly for a long time. Preparation and the right part matter more than the standard on its own.

Are bottom bracket sizes universal?

No. Compatibility depends on the width and inner diameter of the frame shell and on what your crank spindle requires. BikeRadar’s 2025 standards table lists the following shell widths:

Standard Type Shell width
BSA / ISO Threaded 68 mm road, 73 mm mountain, 83 mm downhill, 100/120 mm fat bike
Italian Threaded 70 mm
T47 Threaded 68 mm road or 73 mm mountain
BB86/92 Press-fit 86.5 mm road or 91.5 mm mountain
BB30 Press-fit 68 mm road or 73 mm mountain
PF30 Press-fit 68 mm road or 73 mm mountain

Notice that the same family can show up at several widths. A BSA road shell is not interchangeable with a BSA mountain shell, even though both are threaded.

The exact model and year of your bike matter too. Canyon’s US bottom bracket chart shows BSA 68 mm on some road, urban and commuter bikes, BSA 73 mm on several mountain and fitness bikes, press-fit 86 on many road and gravel models, and press-fit 92 on several mountain models. Even within one brand, you cannot guess.

Example bottom bracket widths by bike type

What type of bottom bracket do I need?

Work through these steps in order.

  1. Check the manufacturer’s specs. Your bike’s technical specifications list the bottom bracket standard. SCOTT, for example, says many styles and sizes are used across its bikes and tells riders to check the model’s specifications or ask a local bike shop.
  2. Look at the shell. Threads inside mean threaded. A smooth bore means press-fit.
  3. Measure the shell width. Use calipers across the shell face to face, and compare with the table above.
  4. Identify your crank spindle. Shimano-style two-piece, SRAM DUB, 24 mm, 29 mm, 30 mm and so on. The bottom bracket bearings must match the spindle diameter.
  5. Confirm the pairing. Shell standard plus spindle gives you the part name. If anything is unclear, ask before you order.

Examples from our catalog

To show how the pieces fit together, here is how some bottom brackets we carry map to shell and spindle types:

The product name tells you the shell. The spindle size and crank type are the second half of the match, so read each listing before ordering.

How tight should a bottom bracket be?

There is no single number. Torque depends on the specific part, and the manufacturer’s manual is the authority. Two examples from the makers themselves:

  • Shimano’s crankset dealer manual specifies 35 to 50 Nm for SM-BB9000 and SM-BBR60 threaded cups, and 35 to 55 Nm for Shimano pedal installation.
  • SRAM’s DUB documentation specifies 50 Nm for DUB BSA bottom brackets and 54 Nm for DUB crank arm bolts.

Use a torque wrench, not feel. Under-tightened cups can loosen and creak, and over-tightening risks damaging threads or the part. If your bottom bracket is from a different maker than your crank, follow the instructions that come with the bottom bracket and check the crank manual for its own bolt values.

Installing a bottom bracket: what changes by type

Threaded installation

Clean the shell, then thread the cups into the frame. Note that the drive-side cup is often reverse-threaded, so confirm the direction in the instructions before you turn anything. Tighten to the specified torque. Because the cups are screwed in, removal is usually just as simple, which is a big part of why threaded systems are easier to maintain.

Press-fit installation

Press-fit cups or bearings go into an unthreaded bore, normally with a dedicated press tool. SRAM’s instructions say to guide the center tube parallel through the shell so it does not touch the frame or cables. Speaking of preparation, SRAM also instructs users to clean the shell of dirt, paint, grease and metal burrs before installing. That step prevents most of the noise problems people blame on the standard itself.

Press-fit installation

If a press-fit adapter shifts under load and creaks, one fix is to reinstall it with retaining compound, as Park Tool’s drivetrain troubleshooting article describes.

What you will need

  • A bottom bracket tool that matches your cups (or a press and extractor for press-fit)
  • A torque wrench with the right range for your part
  • Grease for threaded cups, as the manual directs
  • Clean rags and degreaser for the shell
  • Calipers, if you are still confirming shell width

If you are not set up for it, a local bike shop can install it. A good part still deserves a clean, correct install.

How to know if a bottom bracket is bad

Symptoms are easy to confuse with other noises, so rule out the simple things first.

  1. Tighten the crank bolts and pedals. Bicycling’s bottom bracket creak check says to confirm the crank bolts are sufficiently tight first.
  2. Pedal under load. If the bike still creaks or ticks when you press weight onto a pedal, the source is likely the bottom bracket. Loose or worn bearings are possible causes, and many non-adjustable cartridge and press-fit units must be replaced when worn.
  3. Do the spin test. Singletracks’ bottom bracket service guide says that with the chain off the chainring, a healthy bottom bracket spins smoothly. Rumbling, stiffness, spinning too fast with play, or lateral crank movement indicates a problem.
  4. Match noise to type. Park Tool notes that creaking in a threaded bottom bracket may mean the cups or lockring are not tight, while in a press-fit system an adapter can move under load if the sizing is wrong.

If you cannot settle it, have a shop check it. A creak can also come from pedals, cleats, seatposts or chainring bolts, and chasing the wrong one wastes weekends.

Perspective

Most bottom bracket trouble we hear about is not a bad part. It is a mismatch: the wrong shell width, the wrong spindle, or a shell that was never cleaned before the new bearings went in.

Our advice is to match first, then choose quality. Pin down your shell standard and your crank spindle, then pick bearings built for the way you ride. Riders who put in long road miles, race triathlons or grind through gravel feel a smooth, quiet drivetrain every pedal stroke, and that is why we curate bottom brackets from brands selected for their engineering and rider-focused design.

We also like threaded systems for riders who service their own bikes, since they are generally easier to install and remove. If your frame is press-fit, there are bottom brackets made for it, and careful preparation goes a long way. When you are unsure, send us your frame model and crank type before you order and we will help you narrow it down.

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Choosing a bottom bracket by how you ride

Once compatibility is settled, the choice is about the kind of riding you do.

  • Road and triathlon: Smooth, low-friction bearings suit long steady efforts. A road BSA at 68 mm or a T47 at 86 mm shell, as in our CeramicSpeed listings, are typical matches for modern frames, provided your frame uses those standards.
  • Gravel: Many gravel frames use press-fit 86 or threaded T47, per examples in Canyon’s chart. Mud and water make sealing and clean installation worth caring about. Pair with gravel and cross tires when you refresh the bike.
  • Mountain biking: Shells are typically wider (73 mm BSA or 92 mm press-fit), and the drivetrain sees grit and water. Plan on regular checks, especially after wet rides, and consider your MTB tires at the same time.
  • Bikes you work on yourself: Threaded is the lower-effort path for ongoing maintenance.

A bottom bracket upgrade is also a natural moment to check the rest of the drivetrain: crank bolts, chain, and pedals.

Shop bottom brackets and components at Sport Factory

We stock bottom brackets from CeramicSpeed, Acros and Cane Creek, covering BSA, T47 and BB30 shells for road, gravel and mountain bikes. If you are building up a bike or replacing a worn unit, browse our bike components and match your shell and spindle using the guide above.

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Need the supporting gear too? Our bike category has tools, pumps and lights, so one order can cover the whole job.

FAQ

What type of bottom bracket do I need?

It depends on your frame’s shell type and width and on your crank spindle. Check your bike’s specs first, then confirm by looking for threads in the shell and measuring its width. Our product names list the shell standard to make matching easier.

Are bottom bracket sizes universal?

No. Compatibility depends on the shell’s width and inner diameter and on the crank spindle requirements, and many standards are in use. Even one standard, like BSA, comes in several shell widths.

How tight is the bottom bracket?

Follow the torque value for your exact part. Shimano’s SM-BB9000 and SM-BBR60 threaded cups call for 35 to 50 Nm, and SRAM DUB BSA bottom brackets call for 50 Nm. Use a torque wrench and the manual that came with the part.

How do I know if a bottom bracket is bad?

Tighten the crank bolts first. If a creak or tick remains when you push on the pedal, the bottom bracket is a likely source. With the chain off, a healthy one spins smoothly, while rumbling, stiffness or side-to-side crank play signals trouble.

Is threaded or press-fit better?

Neither wins in every case. Threaded systems are generally easier to install and remove, and press-fit systems can offer more design flexibility to frame makers. Your frame decides which you can use.

Sources