What Is A T47
The T47 is a new bottom bracket standard that has gained popularity among custom frame builders and is starting to be adopted by larger frame manufacturers. It was developed by Chris King with the assistance of others to address the issue of creaking bottom brackets, which should never have been a problem in the first place. Essentially, T47 is a threaded version of PF30. Pressfit bottom brackets have such a negative reputation that someone in the wankateering department came up with the name "Threadfit T47" to make it sound more appealing.
Credit from Hambini
Advantages
Secure
Press fit systems can face issues with the interface between the frame's bottom bracket shell and the bottom bracket cups. With metal frames, BB shell tolerances should be accurately held by using cutting tools post-welding and fabrication. Using a reamer and facing tool can create a perfectly round and faced BB shell, which is essential in steel and aluminum frames. However, this is not possible in carbon frames because once the carbon is set, you cannot use a bottom bracket reamer and facer to set the BB shell bore diameter and trueness precisely.
As a result, a poorly set-up carbon BB shell may fail to hold the cups securely in the frame, causing them to move and create noise. On the other hand, threaded fasteners have been around for over 2,000 years and are a proven system of securely holding parts in place. BSA threaded bottom brackets have one set of threads as a permanent part of the bottom bracket shell, allowing the BB cups to be tightened directly into the frame, preventing any type of movement. When there is no movement of the cups, there is no creaking.
Adaptable
The T47 has a great advantage of adaptability to different crank spindle diameters and frame widths. It can accommodate bearings compatible with 30mm spindle cranks, 29mm DUB, 22/24mm GXP, and 24mm Shimano crank spindles. It offers inboard or outboard bearing configurations to choose from. Press-fit systems have undergone significant developments over the past few years, including shell inside diameters as small as 37mm. However, these small diameter press-fit shells are not ideal for today's larger diameter cranks.
Since each cup threads independently into the frame, T47 cups can be used on any width bottom bracket shell from 68mm to 132mm wide. The width of the shell and the length of the crank spindle are the determining factors for which T47 bottom bracket cups to use.
Stiff
The bottom bracket junction, which is made up of the seat tube, down tube, and chain stays, plays a vital role in the stiffness of a bike frame. Bottom bracket shells with smaller inner diameters, such as BB86, often require wider bottom bracket shells and thicker tubes to achieve the same level of stiffness as the PF30 (46mm) starting platform that can be achieved with smaller diameter tubing. With a T47 shell that starts with a 46mm inside diameter and has no width limitations, frame builders have a sizeable platform to build the bottom bracket area of the frame in the way they see fit to achieve their frame's performance goals.
Dimensions Make Redesign Easier
The T47 bottom bracket shells, apart from providing ample space for bulbous carbon tubes, have the same dimensions as a PressFit 30 shell. This means that it would be easy for engineers to update frame designs from Press-Fit 30 to T47. T47 is an open standard, which means that any frame and component manufacturer can adopt it without any restrictions. This makes it highly likely that T47 will be widely accepted.
Disadvantages
Weight
One of the biggest concerns for most bicycle riders is the weight of the bike. A typical T47 bottom bracket weighs around 180g. To accept T47, the bike will require either aluminum inserts or a sleeve inside the frame, which typically weighs about 100g. The sum of these two components approaches 300g. In comparison, BB86 weighs around 95g, while PF30 weighs around 130g.
Tooling
Other sources have already discussed the tooling required for installing and removing bottom brackets. A specific type of T47 has an 86.5mm shell width, similar to BB86, and therefore has thin flanges for the tool to grip onto. However, using a 2mm tool is not enough as there is a significant risk of it slipping or stripping. Trek, Felt and Factor have stated that they will use this particular variant of T47.
Credit from Hambini
Difference Between T47 and BSA BB
The T47 Shimano setup has a higher level of frictional loss compared to the BSA Shimano setup, which is mainly due to the bearings used. The T47 setup employs the 6806 bearings, whereas the BSA setup uses the 6805 bearings. The difference between these two bearings is small, but still measurable.
In addition to low frictional loss, stiffness is also a desirable characteristic. The BSA Shimano setup is stiffer because of its smaller size and more accurate absolute manufacturing tolerances. However, a pressfit solution such as BB86 is a superior option since it transmits some of the load directly into the frame.
Credit from bigforest
What Is A T47 frame?
T47 is a standard 47mm x 1.0mm threaded shell used on Trek, Felt, and Factor bikes. It's also commonly used on custom builds and comes in a variety of widths.The ICAN Graro Frame is a revolutionary product for gravel enthusiasts who seek versatility, durability, and high-performance. Graro features a T47 Bottom Bracket, which combines the advantages of larger, threaded bottom brackets with improved durability and easier maintenance. This makes it perfect for the challenges of gravel riding.
