This post explains threaded T47 bottom bracket (BB) standard. Look here for explanation of all the other BB standards.
1. Description of T47 standard
T47 is a modern standard with BB cartridges screwed into the frame BB shell threads. Developed by Chris King and Argonaut Cycles companies. Announced in 2015, also known as Thread Fit 30i.
Uses the same 46 mm BB shell diameter as PF30, but the BB is screwed, not pressed in. Threading is 25.4 tpi, or 1 per mm. It can accept spindles of both 24 mm and 30 mm diameter.
It is supposed to eliminate the problem of annoying creaking that external bearings and press fit BBs have, while keeping the advantage of lighter and stiffer spindle.
Great advantage of this standard is that it is compatible with all the modern crankset designs, as long as the spindle is long enough.
2. Expected advantages
- Elimination of annoying creaking that press fit BB standards have (like BB30), along with threaded BB standards with externally mounted bearings (like Hollowtech II).
- Simple and cheap installation and replacement, without expensive special tools.
- Compatibility with most modern cranksets, i.e. spindle standards.
- Open standard that all the manufacturers can freely use.
3. Flaws of T47 standard
The greatest advantage is also the greatest flaw: threading. BB shells need strong metal for thread cutting. This means strengthening (and adding weight) carbon fiber frames. It also calls for new tools in order to cut these new threads, a lot wider than British and Italian standard ones.
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