Walters Hot Take on the Pro’s and Con’s of Thru-Axles​

What is a Thru-Axle?

Before delving into these reasons, let’s discuss what a thru-axle is and how it came into existence. Before we do that, we should discuss what came before. I’m sure we’re all familiar with the mighty quick release. Invented almost 100 years ago by the late great Tullio Campagnolo, it replaced the simple nutted axle. With this, a solid axle was threaded and used nuts to secure each side of the hub to the dropouts. The quick release axle was hollow, allowing for the quick release to be inserted in it. The quick release skewer is a sort of specialized nut and bolt that is secured by a lever actuating a cam. Basically flipping the lever is equivalent to tightening the nut, but with some added mechanical advantage.

The Problem with Quick Releases

Outside of problems caused by user error (and thus causing us all to have forks with so-called lawyer lips on them), the quick release served us well. It certainly fulfilled its initial goal of making for quick wheel removals and installations. There were, however, some changes to the way quick releases were made that made them substandard. In an effort to reduce weight, exposed cams were used and weaker materials employed. Some even lacked the knurled washers that would bite into the dropouts. When these problems coupled with the advent of disc brakes, it was a recipe for disaster.

Disc brakes, as it turns out, put tremendous force on the bike. Especially for the front wheel, the action of braking and releasing can actually cause a quick release to come loose. This was made worse with suspension forks. And yet, mountain bikes at the time were pushing the limits of both braking and suspension. This ultimately led to other problems, including quick release and axle breakages and brake rotor rub as the axle flexed.

How Thru-Axles Work

And that led to the development of the thru-axle to solve these problems. The thru-axle uses not only a different axle design and hub securing mechanism, but also different hubs and dropouts. The hub doesn’t fit into the dropout, so things are quite different. Much like the name implies, the axle goes through the frame. One side has an open hole which then goes through the hub and into a threaded hole on the other side. So the axle in this case is a separate part from the hub.

While it was born out of the most extreme end of the sport, it certainly has advantages for the average user, which is why it is so common on bikes today, including bikes that see much more casual usage. The major problems it seeks to solve can benefit us all: strength and proper alignment of the brake system.

Benefits of Thru-Axles

The biggest reason we can recommend thru-axles is because of the added stiffness they provide. This is sort of a by-product of the added strength. Thru-axles are a larger diameter than a traditional axle and are essentially tied into the frame. This makes them stronger and thus more solid feeling. In our case, because we’re using Boost hub spacing, the front is even a larger diameter than the rear, which gives it an even more solid feeling. Especially on a bike like the All-Packa, which is meant to be ridden off road, it leads to a substantial difference in feel. This isn’t theoretical, but is, in fact, quite striking.

The second benefit is the proper alignment of the disc brake system. Because of the force of disc brakes and the rigors of off-road usage, sometimes a traditional axle will flex slightly and cause the brake to rub. This can cause uneven wear and poor performance. Again because of the strength and stiffness, this is all but mitigated.

Another fine benefit is that there is only one way to put the wheel in. There’s no sliding the wheel all the way in the dropout. There’s no ensuring the wheel is properly centered in the dropout. These are mistakes you can’t make because if you do, the thru-axle won’t go through. Any bike mechanic around could tell you of the countless times they’ve had people with one issue or another that was solved simply by getting the proper positioning of the wheel. This becomes a non-issue with thru-axles.

The Drawbacks

That said, thru-axles are not without some detriments. First your bike frame must be  built with thru axle dropouts in order to use thru axle hubs. There is a vast array of thru-axle sizes out there versus effectively one size of quick releases. This can make finding spares a bit harder. Since the axle needs to be removed to remove the wheel, most versions require a tool and there’s a small chance of losing the axle. They are also slightly heavier. Of course, so are disc brakes, but they are virtually ubiquitous at this point because of their functional superiority. Same logic applies with thru-axles. Finally the thru axle hubs and bike frames are still more expensive than your average quick release hubs and frames.

Conclusion

All in all, the benefits far outweigh the detriments for many people. That said, the addition of thru-axles to the Bike Friday lineup is a most welcome one. Thru-axles are currently available for All-Packas delivered in December or later. All-Packa Frame kits will include the thru-axles. Maybe they will come to more models in the future. Which other Bike Friday models would you like to see them added to and why?