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What is T47 and why it exists

T47 was created to solve one problem: how to run a large 30mm spindle in a large-diameter shell without the creak that plagued pressfit.

The problem T47 set out to fix

Pressfit standards like PF30 gave frame designers a wide 46mm shell that could clear a stiff 30mm spindle. In practice that same width proved hard to keep silent, because a pressed bearing in a smooth carbon or alloy bore has to be held on tolerance alone. Creaking pressfit became a common complaint.

T47 keeps the large shell but adds threads. It is a 47mm interface with a 1mm thread pitch, so cups screw in and clamp against the shell faces the way a BSA cup does, while the 47mm diameter leaves room for a big spindle.

External and internal versions

T47 comes in more than one flavour. External-bearing versions place the bearings outboard of the shell, similar in layout to an outboard BSA setup, and suit narrower shells. Internal-bearing versions tuck the bearings inside the shell for a cleaner look and are used on wider shells.

Shell widths across the T47 family run from roughly 68mm up to about 100mm depending on the frame, which is part of why the standard has spread across road, gravel and mountain frames.

Which spindles it accepts

The headline reason T47 exists is spindle clearance. A 47mm threaded shell comfortably takes a 30mm spindle, and with the right cups it also runs 24mm Shimano and 28.99mm DUB spindles. That flexibility lets a builder pick one shell standard and still support most modern cranks.

So a single T47 frame can host a Shimano 24mm crank today and a 30mm crank later, simply by changing the bottom bracket cups rather than the frame.

Why builders like it

T47 combines the serviceability of threaded cups, no press required, with the stiffness benefits of a wide shell. For anyone who has chased a pressfit creak, the appeal is obvious. It is not automatically better for every frame, but it is a sensible default for a builder who wants a quiet, wide, future-proof shell.

Related

Sources: Wheels Manufacturing · Park Tool bottom bracket reference