Rear Thru Axle ‘Standards’ Are Confusing As Hell For No Reason

I’ve got a stack of thru-axles. None of them is the one I need… WTF?

The bike industry is known for not creating or adhering to standards, but it wasn’t until I needed a rear axle I realized how bad it had gotten. Digging through my bins of collected bike parts, I pulled a not-small selection of rear through axles in what was the correct length and spacing for a 12 x 142mm rear hub.

Looking to upgrade a Kona Raijin 29″ hardtail from QR to thru-axle wheels, I had ordered the dropouts months ago. I finally had some time set aside to do some wrenching, and with a stack of thru-axles to chose from, I figured one of them would get me rolling.

It turns out not a single axle in the bunch was going to allow a bike ride (on this frame) today. Although they were all the correct length and diameter, each axle had a completely different thread pitch. Frustrated, I decided it was time to deal with it once and for all, and headed to a local bike shop that boasts a robust online presence and inventory known for its vast selection of small parts.

What the what? In an ironic twist, the one time I visit my local bike shop, not only did the help at the counter have no idea what I was talking about or what part I needed, (although they were a stocking Kona dealer) but I had to tell him the part I required. Fortunately, I was able to navigate the shop website to identify the part I required, as their site wasn’t working correctly on my mobile device.

Trying to source a rear 12x142mm thru-axle for a Kona CC-142 dropout was a massive headache.

Except it wasn’t in stock; I received the usual script: they could get it for me “in a matter of days.” Thing is, I can go online and order it and do the exact same thing. Plus it’ll be shipped directly to my home or place of work and I wouldn’t have to spend an hour in traffic to deal with it. I wanted to ride my bike today though, so I got in my car and got ready to visit another shop. After driving three blocks I realized the error of this logic, pulled over, and started making some calls. I called three more shops that specialized in mountain bikes, but not a single shop stocked the rear axle I needed to make my bike ridable.

It should also be noted that my partner managed online marketing for two cycling e-commerce websites at the time, and they don’t even list thru-axles on their websites. I’m gonna be bringing that one up at the next happy hour…

I just need a damn rear thru-axle for my bike. How hard is that?

Standards? What Standards?

Well, thanks to the bike industry that could give a shit about the network of independent retailers, we have a crap ton of SKUs to chose from. The result is that no shops in the “bike town” of Portland stock them. Thanks to innovation and product development of the sport. Good job team!

My recent favorite is the VitalMTB’s Inside Line Podcast with Jose Gonzalez at Trek. He compared the bike world to the motorcycle industry, in which everything is proprietary and that the bike industry (well, Trek at least) is moving in that direction. Did the riders ask for that? I can tell you any time I need a part for my motorcycle, I don’t even bother seeking a dealer, as it needs to be ordered online. This means that when you’re traveling and have issues with your bike, you’re going to have to find an online store that will ship overnight and find a place to hunker down while it gets shipped to you. A mechanical or minor crash could easily end an expensive trip. Look, Trek has been making some dope mountain bikes lately. Personally, though, I’m starting to get fed up with this attitude and would prefer to support brands that make life easier.

Seriously, if 2 or 3 brands got together and decided on a number of standards, I’d be on board, and will only buy and recommend your bikes from this day forth. I’ll bet others would too. We’d maybe even make a Facebook group and bitch about those other companies. As long as your bikes don’t suck of course.

Syntace x-12, 12 x 142 mm rear thru-axle for BMC

I have no idea what axle I need

I still wasn’t 100% sure I had identified the actual part I needed, so I started a Google Doc and began the online research. (I wasted a lot of time researching this crap) There are basically three different rear axle types seen as the current “standard” for MTB rear thru-axles. You think there would be three, as there are three distinct rear hub types:

9mm x 135 mm
12 x 142 mm
12 x 148 mm (also referred to as boost)
… oh wait, there is a road one too now. They had to do a bunch of different shit too, because.
Did we forget to mention there is also now “SuperBoost“?

The cool part of the 9 x 135 and 12 x 142 spacing is that many hubs can be adapted to work with both, and you can move wheels between bikes with spare hub caps. The downside is that unless gravel bikes take up this standard, it’s going to fade away.

There are a bunch more though. Boost is new and is quickly becoming the new standard. This doesn’t take into the spacing seen on DH bikes, 12 x 150 mm, or the Superboost spacing (based on the DH width) that Pivot is using. Plus road bikes are now utilizing thru-axles. Do you think they did something like choose one of the existing types? Of course not.

But…no.

How many types of rear axles does there need to be?

In the rear there are basically three types of rear hubs:

10 x 135 mm (or QR)
12 x 142 mm
12 x 148
.. and DH. And road/cross/gravel now too.

Ugh. 3, 4, uh.. I’ve lost count. Logic would dictate there would be three types of rear axles, right? Wrong.

The DT Swiss 12 x 142 mm thru-axle from my Santa Cruz Nomad uses an M12 x 1.0mm pitch.

How to determine the thread pitch on a rear thru-axle

I still needed an axle. Although I also still needed to figure out which one I needed; the easiest solution is to check with the company that makes your frame. Otherwise, you’re going to need to get out the tape measure and calipers and start doing some research.

There are a variety of thread pitches and lengths; in the 12×142 “standard” alone there is a multitude of options. There are a number of variables you’ll need to determine: thread pitch, length of axle, and the thread length. Here are the options I’ve discovered for 12 x 142 mm rear thru-axles:

M12x1.0 — Scott / Santa Cruz
- Fine thread. 168mm length with 12 mm thread length
- Used by Santa Cruz and Scott. Santa Cruz models come OEM with a DT
- M12x1.0, 167mm length with 20mm thread length. Maxle Stealth is available for Santa Cruz / Scott
M12x1.0 — X-12
- 161 mm length
- Used by Specialized. Syntace X-12. Inga’s BMC hardtail uses this.
M12x1.5 — E-Thru
- Shimano rear E-thru 12mm “standard”
- 171 mm length, 18 mm thread length.
- Used by BMC, Giant, Lapierre, Rocky, Yeti, Evil Following, some Kona models (not mine)
M12x1.5 — 160mm length, Road
- 160mm length, 20mm thread length
- Available as Maxle Stealth
M12x1.75 — Maxle
- Rear Maxle used by Ibis, Niner, KTM, some Trek models, a BMC model. Some Kona models too (turns out this was the size I needed)
- 174 mm length. 20mm thread length

This is just for a regular non-boost rear thru-axle. There’s also the boost 148 length. In the 12x148mm “standard” you need to choose from multiple thread pitches as well.

M12x1.5 — Boost E-thru
- 170mm length, 10mm thread length
M12x1.75 — Boost
- 180mm length, 20mm thread length
Plus there are additional lengths for Split Pivot bikes and Trek Boost ABP.

The rear thru-axle from my Evil Following uses a 12 x 142mm, M12 x 1.5mm thread pitch Shimano E-thru standard.

Boost being newer isn’t as much as a clusterfuck. And to think I was frustrated with an additional hub width! At least you can add spacer kits to make your old wheels work as a stopgap measure.

So how do you figure it out? You’ll need to know the length of the axle, the length of the threads and whether its a 1, 1.5, or 1.75 thread pitch. Honestly, it isn’t that bad once you know what you’re looking for – it’s still pretty damn lame though. And you probably won’t find the one you need at your local bike shop, though hopefully they at least stock the sizes to fit the lines they carry. Good luck.

What is wrong with you people?

The problem is there are at least three different thread types utilized. Is it that hard to decide on one? That alone would reduce the amount of SKUs IBDs would need to stock, assuming they wanted to stock it at least.

Part of it is likely due to the ongoing SRAM vs Shimano rivalry. Some frames utilize the SRAM Maxle, others the Shimano ‘E-thru Standard’. I’m sorry, but this isn’t helping anyone. A slightly different length would make sense; I can see the logic there, as all frame materials vary. That said, someone could still make a universal axle that fits most — if we could just agree on one thread pitch. The various thread options though? It doesn’t really make a lot of sense.

Good luck finding a replacement if you lose one. Plus when you’re shopping for a rear axle you have a ton of options. SRAM, DT Swiss and Shimano all offer axles if you can figure out which one you need. Personally, I prefer the bolt-on type, but they all do the same thing. (Prices range from $30 and up)

Solutions

During my trip down the rear axle rabbit hole, I discovered a few new players in the aftermarket axle game. Even they expressed frustration with the current state of affairs. I mean, damn, just to sell you a rear axle they have to make over a dozen and stock them all.

MRP Race Axle

MRP offers hop-ups for anything from fork tuning to chain retention these days. Getting into the axle game, their offering is called the ‘race axle’. Designed as a replacement for heavier QR levers, by switching to their bolt-in model you can drop some weight. At $40 it doesn’t cost an arm and a leg, though it’s a bit more than a Maxle Stealth.

Check it out: www.MRPBike.com/race-axles

Robert Axle Project Lightning Bolt-on axle. 12×142, 12m x 1.75mm thread pitch, 174mm length.

The Robert Axle Project — the Lightning Bolt-on Axle

Designed and made in the US and based in Bend, Oregon, the Robert Axle Project makes — and I quote, “a shit-ton of axles.” I like these guys! Side note, they also sent one of their Lightning Bolt-on Axles to try out, so doubly so. (click here for the review, but long story short, I recommend it)

The Lightning Bolt-on axle is also compatible with the Hexlox security system for riders that lock their bikes in public spaces – it’s definitely worth looking into for this reason alone if that’s something you do.

Seriously though, they just make axles. Check them out at RobertAxleProject.com