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- BSA (English threaded, 1.37" x 24 TPI, 68 mm shell) is the most cross-compatible standard — cheap, durable, creak-free, but heavier and limited to 24 mm spindles unless you use an adapter
- PressFit systems (PF30, BB86, BB92) let manufacturers build wider, stiffer carbon shells at the cost of noise — a press-fit cup in a 41–46 mm bore is a common source of creaks once tolerances drift
- T47 (47 mm diameter, M47 x 1.0 thread) is the modern threaded compromise: it threads into oversized shells that BSA can't fit, supports 30 mm spindles, and is now the default on high-end steel and titanium frames
- SRAM DUB uses a 28.99 mm spindle that fits every shell standard (BSA, PF30, BB86, T47) via adapters — pick the frame, DUB picks the bottom bracket
/ 01
Why there are five standards
A bottom bracket does one job: it lets the crank spindle rotate with minimal friction while staying put in the frame. The reason we have five competing standards is that every manufacturer tried to solve a different problem — weight, stiffness, manufacturing cost, or crank compatibility — and none of them agreed on a single answer.
Threaded bottom brackets (BSA, Italian, T47) screw into the frame. Press-fit bottom brackets (PF30, BB86, BB92) are pushed in with a press and held by interference fit. BB30 is a third beast: bearings seat directly into a machined 41 mm bore in the shell, with no cups at all. Each one needs a different tool, a different crank spindle, and a different install procedure.
/ 02
The five standards at a glance
Shell width, thread/bore, and spindle diameter for each standard. The spindle is what locks you into a crank family.
| Standard | Shell width | Interface | Crank spindle |
|---|---|---|---|
| BSA (English) | 68 mm road / 73 mm MTB | 1.37" x 24 TPI, drive-side reverse | 24 mm (Shimano Hollowtech II) |
| Italian | 70 mm | 36 mm x 24 TPI, both sides right-hand | 24 mm |
| BB30 | 68 mm | bearings seat directly in 41 mm shell bore | 30 mm alloy |
| PF30 | 68 mm road / 73 mm MTB | 46 mm press-fit cups, snap-in bearings | 30 mm |
| BB86 / BB92 | 86.5 mm / 92 mm | 41 mm press-fit cups in wide carbon shell | 24 mm |
| T47 | 68.5 / 73 / 85.5 mm | M47 x 1.0 threaded internal | 24 mm or 30 mm |
| SRAM DUB | any of the above | fitting-specific adapters | 28.99 mm |
/ 03
Threaded vs press-fit: the real trade-off
Threaded bottom brackets almost never creak. The mechanical lock of the threads gives a positive, repeatable fit, and removing the cups for service is a five-minute job with a 44 mm socket. The downside is weight — the steel or aluminium cup adds 30–60 g — and the narrow shell limits crank spindle diameter, which limits stiffness.
Press-fit saves that weight and, more importantly, lets carbon frame builders mould a wider, stiffer bottom bracket junction without machining threads. The cost is reliability: a press-fit cup is held only by the interference fit between the cup and the shell. Once that tolerance drifts — from manufacturing variance, heat cycling, or water ingress — the cup starts moving, and the tell-tale click-click of a press-fit creak on every pedal stroke appears. Repair usually means re-gluing the cup with a retaining compound or, in extreme cases, reaming the shell.
/ 04
Which one should you pick
If you are buying a frame: threaded (BSA or T47) wins on serviceability and quietness. Steel, titanium, and aluminium frames can be threaded at no cost; carbon frames can use T47 inserts to give you a threaded interface in an oversized shell. Press-fit only makes sense if the frame is a dedicated lightweight race bike where the 50 g matters more than the maintenance headache.
If you already own a frame, you don't get to pick — the shell is what it is. Your only choice is the crank: Shimano Hollowtech II (24 mm spindle) fits almost everything with the right BB; SRAM DUB (28.99 mm) is universal across shells via adapters; and true 30 mm spindles (Rotor, RaceFace, some Easton cranks) only work in BB30, PF30, or T47.
/ 05
Tools and torque
Every standard needs its own install tool. Universal kits exist but cost more than a single-socket specialist.
| Standard | Install tool | Approx. torque |
|---|---|---|
| BSA / Italian | 44 mm bottom-bracket socket (HT-II compatible) | 35–50 Nm |
| T47 | T47-specific socket or 16-notch notched cup tool | 40–50 Nm |
| BB30 (bearings) | BB30 bearing drift set (18 mm ID drift) | press-fit, no torque |
| PF30 / BB86 / BB92 | Press-fit bottom bracket installation set | press-fit, no torque |
| SRAM DUB (any shell) | adapter-specific: BSA socket, PF press, or T47 socket | shell-dependent |
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