How to Disassemble and Install the T47 Bottom Bracket Axle

Through years of rider feedback, we’ve compiled this comprehensive guide to help you make informed decisions about the T47 bottom bracket axle system — one of the most confusing yet promising standards in modern cycling.

What Is the T47 Bottom Bracket Axle System?

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” in the cycling world.

Although T47 tried to unify the previously chaotic axle system, it made the required tools more complicated. The thread of T47 is very shallow, and the consequences can be disastrous if the wrong or low-precision tools are used. For riders building up bikes on quality carbon frames — whether you’re working with road bike frames or gravel frames — understanding the T47 system is essential for proper maintenance and assembly.

Who Made a Mess? The T47 Compatibility Problem

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 aesthetically pleasing.

Of course, if there were only the above two specifications, things would be fine — but they 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. This design is very fashionable, but it is not a perfect final solution.

Colnago’s T45 middle bracket placed on the T47 middle bracket shows that they are very close in size, but not compatible — a frustrating reality for mechanics and home builders alike.

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: the axle specifications of the chainring. Common axle specifications are 24, 28.99, and 30 mm, and adding these to the mix makes the situation even more confusing. Whether you’re assembling a lightweight race bike using something like the Permeants ST-09 super lightweight road disc frame or an aero build, getting the right bottom bracket match is critical.

Finding the Right T47 Axle Tools

After a lot of research, 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 various industry estimates, there are approximately 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, and count the number of notches (usually 12 or 16), and then you can go shopping for tools.

Recommended Tool Brands

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, bottom 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 bottom bracket specifications, it will be troublesome.”

According to experienced mechanics, high precision matching with the bottom bracket can reduce the gap between the tool and the outer diameter of the bottom bracket, which helps to produce a tighter fit.

Tackling the Hidden T47 Bottom Bracket

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

Considering the limited space occupied by the bottom 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 bottom 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 true test for the skill 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.

Best Tools 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, and Chris King 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 chainstays. 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 reliable methods below.

Techniques to Prevent Tool Slippage

The first method 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, there is still 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 — 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 axle, the worry about damage to the axle 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 axle. This can protect the sensitive axle 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 bottom bracket.

T47 Bottom Bracket Specifications: The Need for Integration

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

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

If you’re building a new bike from scratch, starting with a high-quality carbon frame ensures better bottom bracket tolerances. Whether you choose an aero frame like the Permeants SA-01 aero carbon road bike frame or a mountain bike chassis from the MTB frame collection, proper bottom bracket installation will save you headaches down the road.

Quick Reference: T47 Specifications at a Glance

• External T47 (68mm shell): Common for road and gravel bikes. Uses external bearings similar to BSA threaded systems.
• External T47 (73mm shell): Used on mountain bikes and some gravel bikes.
• Hidden T47 (86.5mm shell): Internal bearings for road and gravel bikes. More aesthetic but trickier to service.
• Hidden T47 (89.5mm / 92mm shell): Internal bearings for mountain bikes.
• Trek-specific T47 (85.5mm shell): 1mm narrower than standard hidden T47.
• Asymmetric T47a: Used by Factor, Felt, and Cervelo. Threaded version of BB Right.
• Colnago “T47”: 2mm smaller diameter than standard T47. Not truly compatible.
• Crank axle diameters: 24mm, 28.99mm, and 30mm — each may require different tools.

Frequently Asked Questions

What is the difference between external T47 and hidden T47 bottom brackets?

External T47 bottom brackets use bearings that sit outside the bottom bracket shell, similar to traditional BSA threaded systems. They are typically found on frames with 68mm or 73mm shell widths. Hidden T47 bottom brackets have bearings that are embedded within the frame’s bottom bracket shell, offering a cleaner look and slightly wider shell widths (86.5mm, 89.5mm, or 92mm). Hidden T47 systems are more common on modern road and gravel frames where aerodynamics and aesthetics matter.

Can I use the same tools for all T47 bottom brackets?

No, unfortunately you cannot. There are approximately eight different tool specifications for T47 bottom brackets across the market. The tool you need depends on whether your T47 system is external or hidden, the diameter of your crank axle (24mm, 28.99mm, or 30mm), and the specific manufacturer of your bottom bracket. Always measure the outer diameter of the bearing cup, count the number of notches, and measure the distance between diagonal notches before purchasing a tool.

Why does my T47 bottom bracket creak or make noise?

Noise from a T47 bottom bracket usually comes from improper installation, inadequate torque, or contamination between the threads and the frame. Unlike press-fit systems, T47’s threaded design should theoretically eliminate creaking, but low-quality tools or incorrect installation can still cause issues. Make sure to use the correct tools, apply the manufacturer’s recommended torque (typically 30-50Nm), and consider applying a thin layer of grease or thread compound to the threads during installation.

Is T47 better than press-fit bottom brackets?

T47 offers the key advantage of being threaded, which makes installation and removal more straightforward and reduces the likelihood of creaking compared to press-fit systems like BB86 or PF30. However, the proliferation of different T47 specifications and tool requirements has somewhat undermined this advantage. For most riders, a properly installed T47 bottom bracket is more reliable and easier to maintain than a press-fit alternative, provided you have the correct tools on hand.

What torque should I use for a T47 bottom bracket?

Most T47 bottom brackets require a torque of 30-50 Newton-meters (Nm). However, you should always check the specific manufacturer’s recommendation, as some brands may differ. Using a calibrated torque wrench is highly recommended to avoid over-tightening, which can damage the threads or the frame, and under-tightening, which can lead to loosening and creaking during rides.

Get the Right Frame for Your Next Build

Building a bike with the right bottom bracket system starts with choosing a quality frame. At Permeants Bikes, you’ll find a wide selection of carbon frames designed with modern bottom bracket standards in mind. Whether you’re looking for lightweight road racing frames, versatile gravel bike frames, or durable mountain bike chassis, Permeants offers precision-engineered options that make bottom bracket installation straightforward.

Browse the full collection at permeantsbikes.com today and start your next build with confidence. Have questions about frame compatibility or bottom bracket specifications? Don’t hesitate to reach out to the Permeants team for expert guidance.