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What Are Thru-Axle “Standards” and Why Is It So Confusing To Choose the Right Rear or Front Bicycle Axle?

Many people have seen that the bike industry sometimes either does not create or does not adhere to set standards. This can be especially frustrating when trying to find a bicycle axle or thru-axle (through axle). Have you caught yourself looking at bicycle axles and trying to select what you thought was the correct length and spacing for a 12 x 142mm hub? Going through a bunch of bike axles thinking one of them would work only to find that not a single one of them fits?

Although the through axles might have the correct length and diameter, what about the different thread pitch? It is frustrating to say the least. Some of you have probably visited local bike shops, only to find that the person behind the counter has no idea what you’re talking about or what part you need. They might have offered to order you the right part, but what good is that if you have to wait a few days and can order them yourself anyway?

Many online bike stores don’t even list thru-axles on their websites. Why is it so hard to find the right bike thru-axle? We will try to explain to you a little about thru-axles to help clear up the confusion so that you can correctly choose exactly want you need. It is a bit lengthy, so just bear with me.

Many online bike stores don’t even list thru-axles on their websites. Why is it so hard to find the right bike thru-axle? We will try to explain to you a little about thru-axles to help clear up the confusion so that you can correctly choose exactly want you need. It is a bit lengthy, so just bear with me.

Are there even any Standards out there?

One problem with bicycles being produced today is that everything seems to be proprietary. Through axles are no exception. This means that if you are riding and have trouble with your Cannondale bike, for example, you will need to find a Cannondale dealer to help you out. Or if you have a thru axle bike and you need a Maxle thru axle, then you have to use only their compatible Maxle axle on your bike. This is becoming more common and can be extremely frustrating. Even if just a few companies would get together and agree on a few bike thru axle standards it would help tremendously. There are however a few groups that we can place thru-axles in to help differentiate them as we will show you later.

What axle do I even need?

Maybe after all your searching you found the mountain bike axle that you needed. But you are still not 100% that you found the correct part? If you are at this point, you probably have already spent a good amount of time researching.

For MTB thru axles, it seems there are basically four common mountain bike thru-axle types or “standards”. We usually see these distinct rear through axle hub types:

  • 9mm x 135mm (this size is almost obsolete and is no longer seen on new bikes)
  • 12 x 142mm
  • 12 x 148mm (boost)
  • 12 x 150, 12 x 157 (wider hub spacing showing up on downhill bikes)
  • (Plus: Road bikes, Gravel bikes, tricycle axles are also now going with thru axles)

There are actually more mountain bike rear thru-axle types than this in reality. We could say that 12×142 or even Boost (12×148) has become the new standard, but this doesn’t account for the spacing seen on DH or Pivot bikes which can be 12x150mm. Plus, there are BMX bikes, road bikes, tricycle axles, and even mini bike axles, which are switching over from standard bike axles to the use of thru-axles. It seems it was too hard for them to choose from one of the existing standards and stick to it.

What is thread pitch? And how do you find the right pitch for your bicycle frame?

With QR axles you mount the axle on U-shaped drop-outs and then tighten them to keep them in place. However, with thru-axles the drop-outs are closed loop. You push the bike axle through round holes then thread it into one side of the drop-outs. To make things more confusing, this threading on the side can be courser or finer. There are three pitch measurements used currently – 1.0mm, 1.5mm, and 1.75mm. This is very important to get right. Even if you have the correct length through axle, you will not be able to screw your thru-axle into the other side if the pitch is incorrect.

After researching and searching, if you still need to find what bike axle you need, the best and easiest solution is to check with the company that makes your frame. Otherwise, you will need to measure with a ruler and caliper to be sure.

We will try to help further clear up confusion by listing common characteristics of rear thru-axles used today on MTB thru axles.

First starting with 12 x 142mm rear thru axles:

  • M12x1.0 – Scott / Santa Cruz
    1. A fine thread. 168mm total length with a thread length of 12mm.
    2. Used by Scott and Santa Cruz.
  • M12x1.0 – X-12
    1. 160 mm total length
    2. Used for example by Specialized
    3. Has a conical/tapered head instead of a flat one.
  • M12x1.5 – E-Thru
    1. Rear e-thru “Standard” we see from Shimano.
    2. 171 mm total length, with a thread length of 18mm.
    3. Used by BMC, Giant, Lapierre, Rocky, Yeti, and many others.
  • M12x1.75 – Maxle
    1. Rear Maxle axle used by Ibis, Niner, KTM, Trek, and others.
    2. 174mm total length with a thread length of 20mm.

For mountain bike rear axles with the boost length you might encounter the following sizes:

  • M12x1.0 X-12 Boost
    1. 166mm total length
    2. Has a conical/tapered head instead of a flat one.
  • M12x1.5 – E-thru Boost
    1. 170mm total length with a thread length of 10mm
  • M12x1.75 — Maxle Boost
    1. 180mm total length with a 20mm thread length.

I hope already things are becoming clearer for you concerning mountain bike thru axles, and specifically mountain bike rear axles. If you still are having trouble understanding everything we have talked about then at least pay attention to these three things. These measurements will be the best help for you in your search.

So most importantly you need to know the following: the total length of the through axle in millimeters, and whether it has a thread pitch of 1.0, 1.5, or 1.75. Thread length can also be important, but not as important as these two measurements. Usually if we have these two measurements we can find a mountain bike thru axle for you or really any bike axle that you need. If you have a thru axle road bike, we also can find something for you using these measurements. Thru axle hubs now accept many different size axles and we are trying to produce as many standards as we can.

We hope that whether you are considering thru-axles for the first time or replacing the stock thru-axles on your bike that you now feel much more confident as to what to search for. Once you know what to look for it becomes a whole lot less confusing. You might not find the size you need at your local bike store which is why we at HardLite Components are here to help. And if we don’t have what you need, but your axle size could be considered one of the new “standards” that have come out, then we will try to work with you to get what you need into production.

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