Bottom Bracket Standards Explained — Which Frame Takes Which

The Part That Causes More Compatibility Problems Than Anything Else

When we spec a custom build or a groupset upgrade, the first thing we check is the bottom bracket. It's the compatibility chokepoint that trips up more builds than any other component. Here's what you need to know about the main standards in use today.

BSA (British Standard Threaded)

The gold standard. 68mm or 73mm shell width, right-hand thread on both sides. Threaded in, done. You can run any Shimano or SRAM crankset with the correct BB. Replacement is easy. Service life is essentially forever. Most steel frames, many aluminium frames from smaller builders, and some carbon frames use BSA. If you're building a custom frame, we'd recommend BSA for simplicity and longevity.

T47 (Threaded Races, Modern Standard)

Like BSA but with a larger diameter thread and no reverse thread on the non-drive side. Developed by ENVE to replace press fit with something that doesn't creak and doesn't require special tools. Used by many modern carbon frames from Trek, Specialized, and others. T47 is excellent — it threads in like BSA and doesn't creak. If you have a T47 frame, you're in good shape for compatibility.

BB86 / BB92 (Press Fit)

BB86 (road, 86mm shell width) and BB92 (cross country, 92mm) are press-fit standards where the bearings sit directly in the frame shell without threads. Press fit frames are notorious for creaking — the bearings settle, moisture gets in, and the whole system starts making noise. They also require special tools to replace. For service: we can replace press fit bearings, but we always use proper press-fit tools and anti-seize compound.

PF30

Another press fit variant — 30mm spindle diameter, larger shell than BB86. Similar creaking issues and tool requirements. Becoming less common as frame makers move back to threaded standards.

How We Check This

Before we spec any groupset, we measure the bottom bracket shell. We check the type, the width, the spindle compatibility. We tell you what cranksets are compatible with your frame before you buy anything. This check is free — it's part of the consultation before any custom build or groupset upgrade.

The Bottom Line

If you're buying a new frame and the choice is yours: go BSA or T47. They're serviceable, reliable, and don't require specialist tools. If you already have a press fit frame: we can work with it, we just need to know in advance so we can source the right parts.