If all goes well, your mountain bike has two wheels securely and neatly attached to the frame. However, the method of securing the wheels can vary. There are two ways to secure the wheels of a mountain bike: using a thru axle vs quick release. Discovering the advantages and disadvantages of both systems, as well as how they work exactly, is the focus of this article.
Regardless of what your mountain bike is equipped with, it’s also important for mountain bikers to know how to remove their wheels from the frame. This is not only important at home for tasks like maintenance or cleaning your mountain bike, but it can also be incredibly useful on the road if you encounter any unexpected issues.
What is a thru axle?
A thru axle is a hollow tube, typically made of aluminum or steel, used to secure the wheel to your mountain bike. This can be done for both the front and rear wheels.
The type of thru axle your mountain bike has, or which one you need, can vary by brand because there are many different types and sizes of thru axles available.
One end of the thru axle has threads so that you can screw it in place. The other end may have an hex key opening, but it can also come with a lever already attached.
Bottom thru axle: Rear wheel thru axle with hex opening.
Boost vs non-boost
For contemporary mountain bikes with Boost hubs, the most common thru axle size is 12 x 148 mm. For the front wheel, the thru axle is often slightly thicker, typically measuring 15 x 110 mm.
If your mountain bike has Boost hubs, it will also feature a wider and specific Boost frame where both the rear dropout and the fork are wider. This extra width allows for the mounting of wider tires, improving the bike’s handling characteristics.
The hub width is narrower for non-Boost hubs, requiring a different thru axle size. The typical size for the rear wheel is 12 x 142 mm, and for the front wheel, it’s 15 x 100 mm.
Make sure to determine whether you have a Boost frame before purchasing a new thru axle. Also, pay attention to the length of the threaded portion. The threads ensure that the thru axle securely fits into the frame. It must be the correct length to allow for proper and sufficient tightening.
Note: Other hub widths (150 & 157 mm) are also available. Therefore, when buying a new thru axle, be sure to check the specifications and dimensions on your current thru axle to ensure you purchase the correct one.
Mounting and dismounting thru axle on MTB
During maintenance or cleaning of your MTB, it can be useful to disassemble your wheels. If you have an MTB with thru axles, there are usually two options:
- Thru axle with lever
- Thru axle with hex opening (optionally including an hex key tool)
Either the thru axle features a lever or it only has an hex opening. Note that nowadays, many mountain bikes come with a tool integrated into the end of the thru axle, allowing for easy removal. With this tool, you can often also tighten or loosen other components of your mountain bike.
For instance, my 6mm hex key tool also includes T25 and T30 torx heads. This means that with just one tool, I can work on a large portion of the bolts on my MTB if needed while on the go.
Disassembling a thru axle
If your MTB’s thru axle has a lever, you can disassemble it by loosening the lever and then removing the thru axle from the wheel.
If you don’t have a lever, you’ll need an Allen key. Make sure you’re using the correct size Allen key. In most cases, you’ll need a 5 or 6 mm Allen key.
With the Allen key, you can loosen the thru axle. Once the threading is loose, you can remove the thru axle from the wheel.
If you have a lever in the form of an Allen key tool attached to the thru-axle, you can use this Allen key/lever to loosen the thru axle.
If your axle doesn’t have a lever or if there’s no tool provided on the axle, make sure to bring the right Allen key with you when you go mountain biking. If needed during the ride, you can always remove your wheel. Most mountain bikers will use the Allen key from their multitool for this purpose.
Mounting a thru axle
If you’re in the process of maintaining and/or cleaning your mountain bike, make sure to thoroughly clean the thru axle before reinstalling the wheel. It’s also highly beneficial to apply a thin layer of assembly paste to the thru axle, both on the axle itself and the threads. This helps prevent the axle from becoming harder to remove next time or, in the worst-case scenario, seized altogether.
If your thru axle has a built-in tool, apply a bit of assembly paste to the tool to make it more resistant to dirt and water.
Once the thru axle is back in the wheel, it’s important to tighten it securely but not excessively tight. The thru axle often indicates the recommended torque (expressed in Nm) for tightening. In many cases, this will be around 10 Nm. Be sure to use a torque wrench for this purpose. This ensures that the thru axle is neither too loose nor too tight.
For a thru axle with a lever, you need to determine the force yourself. If the lever feels too loose, give the thru axle an extra half-turn. If you can’t tighten the lever securely, then it’s too tight, and you may need to loosen it, for example, by half a turn.
You should also apply a thin layer of assembly paste to this type of thru axle, for the same reasons as with the other type of thru axle.
What are the advantages and disadvantages of a thru axle?
Thru axles offer various advantages, especially when compared to quick release skewers.
These are the advantages of thru axles
A thru axle provides a more stable assembly
A thru axle creates a more stable and rigid assembly, which is only logical. The axle passes through both the frame and the wheel hub, further enhancing stability. If you have a thru axle without a lever, you can still tighten it with the appropriate force as recommended. With a lever, similar to a quick release skewer, it may be slightly less precise.
You can’t position the wheel incorrectly.
With thru axles, you no longer need to worry about whether your wheel is mounted perfectly straight. If the wheel isn’t positioned correctly, you won’t be able to insert the thru axle through the frame and hub.
The mountain bike doesn’t need to be on the ground.
Another practical advantage of thru axles is that you don’t need to place the mountain bike on the ground to reinstall the wheel. Since you can’t reinstall the wheel incorrectly, you can simply leave the MTB in your repair stand and reattach the wheel that way. This leaves both hands free and speeds up the process.
Disadvantages of a thru axle
Of course, there are also disadvantages, although the extent of their impact may vary.
Slower than a quick release skewer.
However you look at it, removing a wheel with a thru axle always takes a bit longer than if the wheel were secured with a quick release skewer. While those seconds may be crucial for professionals in the heat of a race, they likely don’t matter much to recreational mountain bikers.
Don’t forget your Allen key.
If your thru axle doesn’t have an integrated tool or lever, you’ll need to remember to carry an Allen key with you on every ride. Savvy mountain bikers typically keep one in their saddlebag or backpack, often as part of a multitool.
What is a quick release skewer?
A quick release skewer is a system used to quickly secure the wheel to the frame through tension. To properly tighten a quick release skewer, it consists of a spring-loaded mechanism and lever (also known as a cam) on one side and a locking nut on the other.
By turning both parts, you can securely close the skewer, clamping the wheel onto the ends of the frame.
When you remove a wheel with a quick release skewer, you’ll notice that the skewer and the wheel come out of the frame together.
quick release skewers are becoming less common in modern mountain bikes. Entry-level models may still have wheels with quick release skewers. Sometimes, you’ll also see a combination of quick release skewer and through axle, for example, a front wheel with a through axle and a rear wheel with a quick-release skewer.
The most common sizes of quick release skewer for mountain bikes are 100 mm (front wheel) and 135 mm (rear wheel), each with a diameter of 5 mm.
What are the advantages and disadvantages of a quick release skewer?
The advantages and disadvantages of a quick release skewer can essentially be deduced from the advantages and disadvantages of through axles. In principle, the benefits of a through axle correspond to the drawbacks of a quick release skewer, and vice versa.
The advantages of a quick release skewer
Faster
The advantage of wheels with a quick release skewer is that you can quickly replace or remove a wheel. Since high-end mountain bikes no longer use quick release skewers, this hasn’t been a compelling argument in competitions for quite some time.
No tools required
Replacing or removing a wheel with a quick release skewer doesn’t require any additional tools. With some thru axles (without a lever or tool), you need a separate Allen key to loosen them.
Disadvantages of quick release skewers
Less stable
Wheels with quick release skewers are generally less stable. Whether you actually feel this as a recreational mountain biker is debatable. When I had a beginner mountain bike with a quick release skewer on the rear wheel, stability was actually the least of my concerns. The other drawbacks, which you’ll discover below, concerned me a bit more…
Harder to mount straight and with the right tension
When you remove a wheel with a quick release skewer, the wheel simply falls out of the frame. However, remounting the wheel is another story. Ensuring that the wheel is perfectly straight is a bit trickier than with a thru axle. Additionally, you don’t have the option to tighten the quick release skewer to a pre-set torque using a torque wrench.
So, it’s always a bit of a guess how tight it should be. This is also the case with a thru axle with a lever. Too loose is not good, but if the quick release skewer is too tight, you may not be able to tighten the lever enough. So, it’s always a bit of trial and error.
Also, pay attention to the position of the lever when you tighten the quick release skewer. Ideally, the lever should point backward for the front wheel and forward for the rear wheel. If that’s not possible, position the lever so that it causes the least interference while mountain biking and doesn’t protrude unnecessarily, which could catch on things.
MTB needs to be on the ground to remount the wheel
To remount the wheel using a quick release skewer in the best possible way, it’s advisable to place the mountain bike on the ground. This ensures that the wheel falls into the correct position immediately, and the wheel is almost always straight. This isn’t necessary if you’re mounting the wheel while the mountain bike is in a repair stand.
Mounting or dismounting a wheel with a quick release skewer
By releasing the lever, you’ll notice that the wheel will almost immediately come loose from or fall out of the frame.
To remount the wheel, first place the wheel into the frame. Do this not in a repair stand but with the bike on the ground. This ensures that the wheel will be straight in the frame. Then, tighten the locking nut until the lever on the other side provides resistance. You have enough resistance when you can move the lever about halfway.
Then, you need to close the lever to properly tighten everything fully. If the lever is too loose, you must further tighten the locking nut. If you can’t move the lever and fully close it, you need to loosen the locking nut slightly again.
Final thoughts: What is the best choice?
As mentioned earlier, quick release skewers are not as common on modern mountain bikes. However, you still see them on entry-level models, where either both wheels use quick release skewers or where both systems are combined.
For example, my girlfriend’s TREK Marlin has quick release skewers on both wheels. My old Giant had a thru axle at the front and a quick release skewer at the rear. My Scott hardtail and full suspension mountain bikes have thru axles on both the front and rear, and they are equipped with an Allen key tool for disassembly. The thru axle on the hardtail has a lever.
Neither Elke’s mountain bike nor my first Giant considered whether the wheels had a thru axle or a quick release skewer. However, I did consider this for all my other mountain bikes, but since they were in a slightly higher price range, they were equipped with thru axles as standard.
The advantages of thru axles are evident, and it feels more stable in practice. I used to have regular problems with the rear wheel (with a quick release skewer). I have never encountered such issues since switching exclusively to wheels with through axles.
Thru axle or quick release skewer? My preference goes to thru axles. The minimal, and negligible, drawback is not an issue, and I find mounting and dismounting wheels with thru axles more enjoyable. Especially because it’s always correct, and in principle, you can’t do it wrong.
Do you have to give up on your dream mountain bike if it doesn’t have thru axles? Absolutely not! But it could be something to consider, and ultimately, you choose for yourself…
