How to disassemble and install the troublesome T47 axle?

With more and more axle systems launched by various brands, the era of only needing one or two axle removal tools has long passed. In this case, the launch of the T47 axle system is even more "awkward".

In 2015, brands such as Engin Cycles, White Industries, Argonaut Cycles and Chris King tried to combine the easy maintenance of threaded axles with the size advantages of press-fit axles like PF30, thus creating "T47".

This new axle system uses 47x1mm threads and can be applied to metal frames. Since then, with the push of mainstream brands such as Trek, Factor and Felt, the T47 axle has begun to "establish its foothold".

Although T47 tried to unify the previously chaotic axle system, it made the required tools more complicated. As you can see from the picture, the thread of T47 is very shallow, and the consequences can be disastrous if the wrong or low-precision tools are used.

Who made a mess?

The original intention of the T47 bottom bracket system was good, but it didn't take long for its compatibility advantage to be "destroyed" due to lack of communication between manufacturers. As a result, many derivative versions of the T47 bottom bracket appeared, further exacerbating the confusion in the bottom bracket market. Let's take a look at a few examples.

For example, there are two specifications of T47 bottom brackets on the market, wide and narrow. Frames with a bottom bracket shell width of 68 mm (ordinary road and gravel road bikes) and a shell width of 73 mm (mountain bikes and some gravel road bikes) generally use external bearings, a concept derived from British threaded bottom bracket frames. This structure is generally called external T47.

The other wider one is the T47 specification with hidden bearings. The bottom bracket bearings are embedded in the frame with the shell. Usually based on the frame bottom bracket specifications of 86.5 mm (ordinary road and gravel road bikes), 89.5 mm or 92 mm (mountain bikes), it is called hidden T47 bottom bracket. From the appearance, the hidden T47 middle bracket is a true combination of the advantages of press-fit and threaded middle brackets. The middle bracket only protrudes a little from the frame, which is more beautiful.

Of course, if there are only the above two specifications, it would be fine, but things are not that simple. The T47 middle bracket used by Trek has a shell width of 85.5 mm, which is 1 mm narrower than the common hidden T47 middle bracket.

At the same time, Factor, Felt and Cervelo all have models that use an asymmetric T47 middle bracket design (T47a). To put it bluntly, this is actually a threaded version of Cervelo's BB Right middle bracket system. This specification uses a variant of the hidden middle bracket on the left side, while the right side (drive side) is an external plug-in. It has to be said that this design is very fashionable, but it is not a perfect final solution.
▲Colnago's T45 middle bracket is placed on the T47 middle bracket. It can be seen that they are very close, but not compatible.

Let's take a look at Colnago. Its own T45 bottom bracket system only lasted for two generations of models. In order to adapt to the changes in the bottom bracket market, Colnago was also "forced" to follow the trend of T47, but it also retained the little personality of Italians.

The "so-called" T47 used by Colnago only looks like it, but its diameter is 2 mm smaller. In addition, Colnago intends to provide users with threaded to press-fit bottom bracket conversion parts to install BB86 press-fit bottom brackets. And because of the well-known abnormal noise problem of press-fit bottom brackets, it is not known what the intention is.

In addition to the various T47 specifications, we may have forgotten one thing, that is, the axle specifications of the chainring. Common axle specifications are 24, 28.99 and 30 mm, and adding these will be more confusing.

After a lot of torture, when you find the T47 bottom bracket that suits your frame, you also need to consider the applicability of the tool. That's right, there is no unified tool standard for the T47 bottom bracket. According to the author's statistics, there are about eight tool specifications for installing and removing the T47.

Finding the right T47 axle tool is a headache. As bearing and axle diameters change, most T47 axle manufacturers will design different tools for external and press-in types. In addition, the diameter of the crank axle needs to be considered.

Since external T47 axles usually use smaller diameter installation tools, compatibility is relatively good. External T47 axles for Shimano 24mm axles generally use conventional 46.2mm diameter, 16-notch tools. Such tools are widely applicable and can be compatible with many center lock discs, old Shimano axles, and other external axles.

Even if the crank axle specifications come to 28.99 or 30mm, the external T47 axle can share tools with axle specifications such as BSA30 and external DUB. According to the brand of the axle, it can help you identify the required tools faster. In addition, it can also be distinguished by measurement.

All you need is a mechanical ruler or a set of calipers to measure the outer diameter of the bearing cup, the distance between the two diagonal notches (as shown above), and count the number of notches (usually 12 or 16), and then you can go shopping for tools.

I like Abbey Bike Tools because it has a wide selection of tools and detailed size charts to help you judge the match. This brand is expensive, but the installation quality is second to none, and it can effectively prevent damage to the bottom bracket and frame.

Another good tool brand is WCM (sold by DIY-MTB in Australia). This brand is a little unfamiliar to many people because it is mainly sold on eBay. This brand also offers a wide selection of installation tools, including sockets and wrench-style tools, and is affordable. Its tools look like semi-finished products, but the quality is trustworthy.

Common tool brands such as Wheels Manufacturing, Park Tool, Unior, WolfTooth and Cyclus have launched installation tools for T47 bottom brackets, although they have slight differences in how good they are. In addition, middle bracket brands such as Enduro, CeramicSpeed, Chris King, and Hope also have their own tool products.

When buying tools, you need to be careful and try to avoid buying tools that claim to be suitable for multiple specifications. Jason Quade, founder of Abbey Bike Tools, said: "If a tool is suitable for multiple sizes of middle bracket specifications, it will be troublesome."

According to the author's experience, high precision matching with the middle bracket can reduce the gap between the tool and the outer diameter of the middle bracket, which helps to produce a tighter fit.

For the external T47 middle bracket, the solution is relatively simple, generally only three specifications of tools are needed. But the real headache and frustration is the hidden T47 middle bracket.

Considering the limited space occupied by the middle bracket system, frame designers are trying to maximize the width of the frame to maximize stiffness and tire clearance. And transmission component manufacturers are trying to reduce the crank Q value and chain length.

The benefits of the press-fit middle bracket are highlighted here. It does not require an external shell and can effectively save space. Let's take a look at the hidden T47 axle, which retains some of the advantages of the press-fit axle, but at the same time retains the shallow tool teeth.

The exposed tool teeth on both sides are generally only 2 mm thick, which is risky for installation and removal and is a test for the level of technicians. Considering that many T47 axles require 30-50Nm of torque, you need to keep the tool from slipping when exerting force. In addition, if you have stronger requirements for the torque value of the axle, there are almost no tools that can do it.

To solve this problem, Trek uses a 0.5 mm wider tool tooth for the T47 axle to facilitate technicians to install. Although the difference of 0.5 mm is negligible, it is at least better than the original 2 mm width.

At the same time, several T47 axles have tried to eliminate the isolation area between the tool teeth and the frame to make the tool contact surface as wide as possible. However, this also increases the risk of damage to the frame paint under heavy operation.

What tools should be used for hidden T47 axles?

For the hidden T47 bottom bracket, the first consideration is good tolerance and precision. Good quality tools such as Abbey Bike Tools, Enduro, Wheels Mfg, WCM, Wolf Tooth, Ceramic Speed, Chris King, and a few high-priced tools have obvious advantages.

You can choose a socket to install and remove the T47, but it is easy to tilt and slide. For this kind of bottom bracket with shallow tool teeth, the best tool is actually a wrench. Compared with a socket, a wrench-type bottom bracket tool can provide a completely vertical force. However, the available leverage of this wrench tool may be limited, and there will be clearance problems when using it on models with wide chain forks. You can choose according to the specific situation.

Let's go back to the socket tool. Using a tool with high precision and ideal tooth depth can effectively prevent the problem of the socket falling off. The most basic prevention method is to hold the socket with your other hand during disassembly and installation. This also requires some skills, but it is not guaranteed to succeed every time. There are two more ways below.

The first is to use a tool with a locating hole that snaps into the bottom bracket bearing to help keep the tool in place. Both Ceramic Speed ​​and Enduro offer such tool solutions, with the former using a clever removable magnetic sleeve that accommodates 24, 28, 29 and 30mm bearing sizes. However, under high torque conditions, the author of this article still found that there was a risk of the sleeve coming off, but it is better to have it than not, so the second method is more recommended.

The second solution is very simple and old-fashioned, but it is reliable enough. It comes from the era of square-hole bottom brackets. Using a tool to pull the bottom bracket from the other side can effectively fix the removal tool, and it can be said that there is almost no risk of it falling off. In recent years, similar bottom bracket removal tools have appeared, such as the design with a bolt inside.

Regardless of which tensioning method you use, Jason Quade recommends using a more elastic spring on the other side, which will help maintain the tension of the bottom bracket removal sleeve, which is a very effective technique.

Of course, even if you buy these expensive tools and use the tightening method to fit the sleeve tightly to the middle shaft, the worry about the damage to the middle shaft and frame caused by the tool slipping and misalignment cannot be perfectly solved.

Another suggestion is that it is best to put a layer of paper between the sleeve and the middle shaft. This can protect the sensitive middle shaft teeth and will greatly reduce the damage to the frame paint caused by mistakes. If you are obsessive-compulsive and think that this is not enough, you can also 3D print a gasket to prevent the sleeve from causing any scratches on your new middle shaft...

T47 middle shaft specifications need to be integrated

In theory, the larger thread structure advantage of the T47 middle shaft is not bad. But in practice, due to the many specifications of the external and hidden T47 middle shafts, coupled with the different tools used, it has caused a lot of trouble for bike shop technicians and individual enthusiasts. I also hope that a better integration solution will appear in the future.

For the author of this article, the press-in middle shaft is easier to use from an operational perspective. When the frame paint is very close to the exposed part of the middle bracket, the difficulty of disassembling the T47 middle bracket increases sharply. But thankfully, the latest tools for shallow teeth have greatly optimized the disassembly and installation experience of the hidden T47 middle bracket.