Six reasons to like the T47 bottom bracket standard

Here’s why this BB standard could be different

From the comments on our recent story about the emerging T47 bottom bracket standard it’s clear that riders are fatigued and, quite frankly, fed up by the frequency with which manufacturers are changing component standards.


To some cyclists, it may seem like the new T47 bottom bracket standard amounts to little more than taking two steps forward and one step back, but there are some potential benefits to this system that make it very appealing.

Here are six reasons why it could be the bottom bracket standard that saves the cycling industry from itself.

1. Threads work

Plan and simple, threaded bottom brackets have worked for most of cycling’s history. It’s a tight interface that has proven reliable and effective – more so than many of the current press-fit standards.

2. It’s designed for versatility

T47 bottom brackets, such as Chris King’s Thread Fit 30i, can accommodate cranks with 30mm as well as 24mm diameter spindles, through the use of adaptors. Riders won’t have to worry about whether or not their go-to crankset will be compatible with their new frame.

3. It could fix creaky press-fit frames, so long as they’re metal

The T47 standard is essentially a PressFit 30 shell with threads.

The internal diameter of a PressFit 30 bottom bracket shell is 46mm. A T47 shell has an thread diameter of 47mm with 1mm threads mated to a bottom bracket with an outside thread diameter of 46mm with 1mm threads.

This means it would be possible to cut threads for a T47 bottom bracket into steel and alloy frames. We caution that just because this is possible, it does not necessarily mean it is the best course of action, considering it will void your warranty. 

4. Oversized sizing keeps things light and stiff

The fact that the t47 standard is essentially a threaded press-fit 30 bottom bracket bodes well for its acceptance:

Modern tube shapes often require an oversized bottom bracket shell 

As stated above, a T47 bottom bracket shell is approximately the same diameter as a PressFit 30 shell. One of the reasons PressFit 30 became popular with frame designers is that it allows for greater surface area at the critical junction of the down tube, seat tube and chainstays – an area of the frame where stiffness is paramount. This increase in real-estate means designers can use thinner-walled tubes in large diameters to keep frames light and stiff. T47 provides these same benefits in a (hopefully) less creak-prone package.

5. Dimensions make redesign easier

In addition to providing a large amount of real-estate for bulbous carbon tubes, the fact that T47 bottom bracket shells share the same dimensions as a PressFit 30 shell mean that it would be relatively painless for engineers to update frame designs from Press-Fit 30 to T47.

6.    Open to everyone

T47 is an open standard, meaning any frame and component manufacturer is free to adopt it. This bodes well for its acceptance.


What do you think?

Would you be willing to accept yet another bottom bracket standard? Share your thoughts in the comments section below.