142x12 thru axle Trek ABP MTB

There has been a lot of talk in both the industry, the media, and forums lately about the new mountain bike axle standard of 142×12. While there is an abundance of good information available, there are also a ton of misconceptions. Clearly there are some new concepts in play, though perhaps most alarming to the general public, is a perceived assault on the current standard: the 135x10mm (also known as 135 x 5mm, 5mm is the quick release diameter, 10mm is the axle, or drop out diameter) quick release rear wheel. Consumers are up in arms over the fact that there is a new “standard” that will obsolete their current set ups, only to force them into new wheels.

This thinking is understandable, but in reality, manufacturers have gone out of their way to make the new crop of mountain bikes backwards compatible, and offer hop up kits for current hubs to make the jump. When it comes to “why,” there is a lot to digest, but simply put – it has the potential to be better.

Get the full skinny on the fat axle, after the break!

The Beginning.

Let’s go back. Way, way back, 1927 to be exact. Wing nuts were still used to secure bicycle wheels at this point, and it was here, on the side of the snow covered Croce D’Aune Pass,  that Tullio Campagnolo would find the inspiration for a bicycle component that is still used today. After losing valuable time in a race, due to the inability to remove the wing nuts on his wheel because his hands were so cold, Tullio eventually designed and created in 1930, what we know today as the modern quick release.

While Tullio was certainly ahead of his time, and an inventive genius, he couldn’t possibly have imagined the manner in which mountain bikes are ridden today. Sure, manufacturing methods, and both frame and hub construction have improved, but essentially, many of us are still riding on a 80 year old design, originally conceived for road bikes.


142x12 Axle installed on 2011 Trek Fuel EX 9.8

Why Thru Axle?

As mentioned above, the current mountain bike rear QR axle system is horribly out dated. Due largely in part to the advent of disc brakes, modern suspension, and excellent tires, riders are able to bomb descents faster than ever thought possible in addition to catching some serious air time. The larger diameter thru axle allows for more strength, stiffness, and ease of use. Ever tried to explain to someone how a quick release works? It is much easier to explain how to use a QR thru axle by saying, “turn this until it stops, then flip this lever.” While weight is always a concern, the larger diameter of the thru axle allows for it to be made of aluminum which causes only the smallest weight penalty when compared with the average QR set up. Safety is also a foremost priority, so the fact that a thru axle is captured in the frame, virtually guaranteeing against wheel ejection is obviously a plus.

However, the goal of 142×12 wasn’t necessarily to improve stiffness, yet offer an easier to use interface for consumers. Traditional thru axles required the axle to be clamped both axially, and radially which was usually accomplished with a handful of pinch bolts – not simple. The hope for 142×12, was to create a system that could be installed easier than a quick release without any tools (once adjusted) and once installed would provide a safer method in which to secure the wheel to the bike.


Why the 12mm axle?

12mm refers to the diameter of the axle itself (the part that replaces the QR), how did manufacturers come up with the 12mm axle size? For starters, it’s been used for DH bikes for years, but more importantly it is basically the largest axle that will still fit through a modern cassette lock ring, and disc brake rotor. This becomes even more important, with the current experimentation with cassette gears as low as 9t. Obviously, consumers are already upset by the fact that there is a new rear wheel spacing, so the wise decision was made to accommodate current cassettes and rotors.

142x12 dropout. Notice the 3.5 mm deep slot in the dropout, this is what gives the wheel it's easier self-centering installation.

135x10 QR dropout. This also has the 3.5mm slot, but it is only 10mm wide to accommodate the smaller QR hub.

Why 142mm rear spacing? Wasn’t 135 good enough?

This is perhaps the most controversial issue of the entire transition, as it involves a new “standard.” This measurement is the actual width of the hub from end to end, and standard MTB rear spacing has been 135mm. If you were to compare the same wheels, with one being a 135×12 hub, and one being a 142×12 hub, they would have the exact same measurements aside from the OLD (Outer Locknut Dimension). That means the same flange spacing, chainline, bearing placement, everthing. So what gives?

The key here is ease of installation. The goal of the entire 142×12 movement was to produce a system with the ease of wheel installation like a quick release, but the strength and stiffness of a thru axle. In order to accomplish this, the frame and wheel have to be self-centering which requires a recess in the frame for the hub to rest.

Most rear thru axles (150mm and including 135×12) up to this point are non self-centering, meaning you have to hold the wheel precisely in place with one hand, while you insert the axle with the other. This usually works better in theory than in practice, and definitely isn’t easier than a quick release when it comes to installing the wheel. When it comes to a self centering wheel, you can install the wheel in the frame and place it on the ground and the wheel will center up perfectly, allowing you to close the quick release. Personally, every bike I have had with a non self-centering thru axle has been an immense pain, not due to the frame, but due to the hub end caps wearing out and falling out of place every time you go to install the wheel. Of course, there will be those out there who don’t see the need for a self-centering rear wheel, but in order for mountain bikes to be sold to the masses, it is a must have.

Clearly, self-centering is the way to go, but what does that have to do with a wider, 142mm rear end? The issue here is the fact that in order for the necessary 3.5 mm of inset on the dropout for the hub to rest, 135 simply won’t work. If you were to try, you would find that either the cassette or the chain would rub on the seat stay or chainstay, due to how little clearance there is between the two. So, the only answer was to add as little to the width of the hub as possible, 3.5 mm per side, in order to attain proper clearance, hence, 142mm.



So why 142mm and not 150, or bigger?

The obvious answers here are Chainline, Q-factor, and required bottom brackets. One of the benefits of retaining the same basic measurements as a 135mm spaced hub, is the fact that it has no bearing on chainline, Q-factor, or the need for a different bottom bracket. Going to a 150mm spaced rear hub would require changes to all of the above, and as it is, XC rider are already clamoring for narrower Q-factors. In order for proper chainline on a 150mm spaced rear hub, an 83mm bottom bracket would be required which would both increase Q-factor, limit the amount of compatible cranksets, and add weight.


Trek's ABP Convert hardware. Run either 142x12 or 135x10 QR on the same frame by simply changing out the hardware.

What does all of this mean for my current bike and wheels?

Honestly, it all depends on what you have. When it comes to wheels, many manufacturers will offer wheelsets that are compatible with both standards from here on out. By simply switching endcaps, or an axle, wheels will be able to transform from 135×10 to 142×12. The only caveat comes down to the size of the bearings in the hub. The original Easton Havens for example, had bearings that were physically too small to fit a 12mm thru axle through, so no conversion option for them. Of course, this means that with hubs such as these, even if the spacing of the rear wheel hadn’t changed, there would still be a need to buy new wheels to run a 12mm thru axle. The latest version of the Havens however, were designed with larger bearings to accommodate the conversion kit. While not every wheel will have the option of converting, just because you currently have a quick release rear wheel doesn’t necessarily mean you would have to buy a new wheelset to run 142×12.

The photos above show the 142×12 conversion kit for the 2011 Easton Havens. The axle kit is incredibly easy to install and basically requires one Allen wrench and a 20mm cone wrench. There is also a 135×12 adapter available for the Havens which installs in the same manner.


On the frame side of things, many (not all) manufacturers are graciously building them so they are backward compatible with 135×10 QR wheels. Trek is one of those companies, and offers two different 142×12 axle systems: ABP Convert, and ABP FR. In the case of the 2011 Trek Fuel Ex 8 and above, the ABP Convert system comes stock with the 142×12 set up, but also includes the hardware to run a 135×10 QR. Trek’s option to accommodate this is to build two sets of ABP (Active Braking Pivot) hardware, so you can swap out the hardware in the frame and run either 142×12 or 135 QR. ABP FR on they other hand, gives rides the ability to choose between 142×12 and 135×12 on bikes such as the Trek Scratch.

Other bike makers, such as Yeti, instead opt for a complete replaceable drop out system which gives even more rear wheel freedom, as it even makes set ups such as sliding single-speed drop outs possible. As stated, not every manufacturer is building in the backwards compatibility, but for those who are I feel it is commendable, and illustrates said companies ability to empathize with consumers in regards to changing standards.

Pros of 142×12:

  • Larger captured axle means stiffer, stronger rear end and less deflection of rear hub
  • Easier wheel installation than 135×12 or 135×10 QR
  • Due to its design, the thru axle satisfies CSPC wheel retention requirements in an extremely simple and repeatable manner
  • Design guarantees the same wheel alignment each time the wheel is removed and installed
  • Some current wheels and frames are compatible with adapter kits
  • Retains the same chainline as 135 QR wheels, which means no bearing on Q-Factor (going to a wider hub, say 150, would require the use of a wider BB, therefore increasing Q-factor)

Cons of 142×12:

  • Obviously it is a new standard which may, or may not require new wheels
  • Most 2010 and prior frames aren’t compatible
  • Currently, most 142×12 bikes are not rear-wheel trainer compatible (not so much an issue on full suspension trail bikes, but more so on  future XC hardtails)
  • New bearing size for freehubs has the potential to negatively affect bearing longevity

Clearly, with the amount of brands on board that are slowly introducing 142×12 bikes and parts over the next few years, it seems the “standard” isn’t going anywhere. What’s important to remember though, is that just because more and more bikes will be shipping with the larger axle, that doesn’t mean the end of the 135mm quick release as we know it. No one is forcing the upgrade on anyone, but for those who want it, it’s there. The idea of being forced to buy new parts is a somewhat moot point due to the fact that if you are buying a bike with 142×12 it will have everything you need already. Even if you already have a set of high end 135×10 QR wheels, there is a good chance you will still be able to use them with the conversion kits offered by many manufacturers. Also, those interested in upgrading their wheels now, who don’t have a 142×12 frame yet (but my in the future) will have the option to purchase wheels that are compatible with both standards. Nearly every possible concession has been made by manufacturers to ensure the most painless transition for consumers as possible.

Does everyone need the benefits of the larger axle, and simplified installation? Of course not, but there are those who will benefit more than others, and in the end – if it makes mountain biking safer or easier, we all win.

So what are your thoughts? Have you ridden a bike with 142×12? Plans to buy one in the future? Tell us below!


  1. michael on

    I have a 15mm thru-axel on my fork, which far superior to standard QR skewers.
    It only makes sense to final update the rear axel.
    When I get a new bike I want a 142×12 rear axel

  2. James on

    “So what are your thoughts? Have you ridden a bike with 142×12? Plans to buy one in the future? Tell us below! ”

    My thoughts in order when I started reading this article were:

    “There has been a lot of talk about this? Where? I hadn’t seen it.”
    “Wait, there is a standard? Is this like the industry agreed upon 3 or 4 standard front axle sizes? Nothing like a brand specific unique standard to keep prices high and compatibility low.”
    “No mention on how this impacts trainers. Getting a bike fitting with this new “standard” must be awesome.”

  3. ZachOverholt on

    @ James
    142×12 is not brand specific. Also see Con #3. “Currently, most 142×12 bikes are not rear-wheel trainer compatible (not so much an issue on full suspension trail bikes, but more so on future XC hardtails)”
    Thanks for reading!

  4. Possumrider on

    My first all mountain rig, GF Fat possum had 20mm thru axel up front, sweet riding super stout bike w/ huge stomp and squat capabilities.It just felt better. Down side was I stripped out QR and needed to replace after one year. Second issue split the bottom bracket on an XC ride, I had to replace the frame and rebuilt for private sale. Now focussing on XC and riding a 1×9 converted 2011 Rig, thankful my Industry-nine wheels were compatible with 2011 replacement frame for my Rig. Now if I could just get a derailuer hanger to complete my 1×9 conversion. TREK are you out there listening??? As far as the 142-12 standard, I say bring it on boys! Anything to help keep these things in one piece is helpful, I average two broken frames per year since I started riding in 2006, good thing I’m a “master” rider or I’d really be wearing these things out??? East coast Rocks, XC bike, and “JAR”=warranty replacement (l:-D
    possum out

  5. Chris on

    I have a 142×12 on my Cube Stereo 140mm bike and I absolutely love it. It’s a super stiff rear end and tracks really well with my 20mm TA front fork. I had the 15QR front but didn’t think it was stiff enough for super hard cornering, so I went back to the 20mm. I’m running a 1×9 setup so the chainline is nearly perfect. The wheels I’m running are the Notubes Flow ZTR with their own hubs and the rear hub can either run the 135mm spacing or the 142mm. The entire bike weighs in at just below 29lbs.

  6. Ed on

    Not sure how bearing size of these hubs will negatively effect longevity? These hub are going to have a larger bearing in them so in theory the bearing should have a positive effect on longevity (as larger bearings can handle the forces of riding better and have more surface area so shouldn’t wear as fast).

  7. ZachOverholt on

    @Ed basically it is only a concern for the bearings in the freehub. They can’t get any bigger so the ID is increased resulting in the use of smaller ball bearings. However, DH bikes have had these axles and bearings for years so most likely it won’t make a noticeable difference.

  8. Spandrew on

    Bikes with the 142×12 don’t fit into a trainer…big deal.

    Most of the bikes coming with this axle set-up are aimed at trail/all mountain and longer travel… targeted at more aggressive riding. Realistically, are those types of riders going to hop on a trainer in winter? I doubt it. They’ll either keep riding or shralp the ski hills. Also, most of the bikes coming with the 142×12 are high end bikes. If somebody can afford one, and is serious about riding (enough to ride a trainer) I’d imagine they have more than one bike. Just my 2 cents.

  9. Ganbei on

    9, 15 or 20mm on the front fork makes a huge difference, so 12mm in the back, yeah why not, I’m a true believer!

    As for 142mm…~~. Mucking round with the rear spacing just seams like the end user is being hit up again to comply with a new “standard”. Surely other allowances could have been made in the rear dropouts or the design of the axle that would accommodate alignment of the wheel without having us forking out more bobs on spacers, additional parts, etc..

    The goal of “offering an easier to use interface for consumers” has not been achieved. The addition of the new option only complicates matters in a industry were anybody with “new technology” can create a new standard….. the end user always gets hit in the pocket.

    Rant over..

  10. Morpheous on

    Makes sense,why the incredibly slow adaptation oftechnological updates in the bicycle world. strange and ironic. Great article! Very pertinent and helpful.

  11. ZachOverholt on

    Scott, do you have a part number, or link, or something on the kit? I heard that they were working on a fix, though I didn’t know it was available yet.

  12. Lance on

    Specialized has gone a step further with the 142mm hub and moved the nondrive side flange outward, allowing them to build a wheel with less dish. This makes the wheel stiffer laterally, as well as increases strength and stability of the wheel build.

  13. Varaxis on

    Quite a few hub makers did that Lance. Bontrager’s FCC design has that, but they don’t market it as heavily as Specialized. They even take it further than Specialized and make the flanges taller. A little research goes a long way to avoid being sold on such marketing and not getting your money’s worth.

  14. Teekay on

    Quote “why the incredibly slow adaptation of technological updates in the bicycle world…”.
    Simple – we’re idiots. After all the years of investment and innovation by Fox/Marzocchi/Shimano/SRAM etc some of us still ride hardtails, singlespeeds and rigids. We obviously don’t like change!

    Bit more seriously – I wonder how many folk have lost their standard QR back wheels, or even front? After 15 years of this stuff, getting progressively more and more adventurous together with the people I ride with, I’ve never seen one or heard of it happening. Change is just a cash generator for most manufacturers. I didn’t go to my LBS and ask them to create a big axle for me, who on earth did?

    Oh, one other small point – it took me a good few years to get all my bikes able to swap wheels at very short notice, which has been extremely useful and necessary at times, but I can only do this because my current frames (inc EX9 and Top Fuel 9, luckily) all accept standard QR.

  15. Kayakjack on

    Mostly, the customers do not ask for these things. The manufacturers sit down and ask themselves ‘How can we improve this, how can we make it easier to use and how can we make it cheaper to build?’
    It’s called ‘Research and Development’. If they didn’t do this we would all be riding around on skinny steel tubed bikes with 15 speeds and no suspension!

  16. Andrew on

    I just purchased the Kona Hei Hei DL and I am very disappointed that it has the 142×12 hubs. I just found out that the bike hubs are not compatible with any bike trailers on the market. I was planning on doing the GDR and using a trailer. Anyone who plans on using there mountain bike in conjunction with trailer needs to be aware of this. The bike manufactures are intentionally not disclosing this.

  17. Brian on

    Another significant CON for me is that my 142×12 front wheel no longer fits my expensive and excellent Thule car-top bike carrier without another expensive conversion device. All major brand carriers are the same, from what I’ve seen. Considering this thread started in 2011, and its not 2014 and as far as I’ve seen, no quality company has made a fork mount bike carrier with 142×12 standard, I’ll assume we’ll be dealing with this for awhile….

  18. DasGuy on

    Brian, if you get this. You probably will never see them make a 12mm fork mount as there are no 12mm fork axles. There are 15mm and 20mm fork axles.

    Which segways right into why halfass is with 12mm when fronts are already 15-20? Maybe this is just to ween people off the last of the old road bike gear, the older a standard is the more people tend to dig their heals in.
    It seems like it wouldn’t be that much more work to just go clean slate and use a proper 145x20mm as the base with provision for hubs to have different chain lines(not necessarily on the same hub). I mean hey the only thing not being redesigned is the friggin’ cassette splines.

    Lance you have the notion of dishing backward, moving the non-drive side flange more outboard and or making the non-drive side flange larger, creates more relative dish and tension imbalance. They do that only to allow wheel builders to use the same length spokes on both sides for manufacturing costs. Some hub makers make the drive side flange much larger, helping to reduce the tension imbalance, if combined with an offset spoke rim dish can be greatly reduced.

  19. Chris on

    Having to use a fork mount adapter will likely always be the case, as you can’t then use the same carrier for a 9mm QR fork. This would mean people with road bikes as well as MTB would need two separate carriers. It just wouldn’t make sense to force people to have that setup.

    What I don’t like about having to use an adapter with my thru axle fork is that my bike is no longer securely locked to my carrier. The adapter is secure but anyone can just release the TA quick release and take my bike. So a con there is that I have to use a cable lock to secure my bike to the roof rack.

  20. Jami dh on

    i ask… why? why create new standart every year? why is the reason for call it “standart”, because, actually we have a lot of standart so its no sense, call it standart its just a new measure, but nos an standart…
    for me, the standart die the day when someone decided that change a measure its goos idea for make money.

  21. SteveH on

    So. Can someone in the know help me out here!!??

    I have a Niner RIP 9 frame with 135 x 10 rear drop outs.

    I have a set of wheels off a Commencal that are 142 x 12 on the rear. It’s a Joytech disc light hub.

    Is there any way I can make these compatible with a hub converter or do I need to buy a new rear wheel…?

    Niner I believe can sell me a new pair of drop outs with 142 12 spacing but want £90 for them. Seems a little steep for two poxy brackets to me?!

    Help would be greatly appreciated

  22. Paolo on

    I have a trex superfly 9.6 MY 2015
    I have the QR 5×135 in the rear
    can I switch to 12×142? in case of positive feedback, what are the components that I have to buy?

    Paolo Mazzelli


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