12mm Thru Axle for Kid Trailer

(55 customer reviews)

$ 58.00

Robert Axles for Kid Trailers are designed specifically to fit your 12mm thru-axle bike and allow attachment of any hitch-mounted trailer. These fit any trailer that has two wheels and a single point of attachment to the axle. This includes all the two-wheeled child, pet and cargo trailers such as: Thule, Chariot, Burley, Instep, Carry Freedom, and many more.

Purchase our Kid Trailer axle for your bike. Share your stoke for cycling with your kids. Simplify your life by allowing quick and secure attachment of your trailer to your best and favorite bike. Enjoy the adventure.

SKU: KID213 Category:


Since 2013, we have been an important part of cyclists’ adventures all over the world. Our axles have millions of miles on them in mountain bikes and road bikes, carbon bikes, fat bikes and e-bikes. Our axles are specifically designed to handle the high-torque loads generated by e-bikes.

Your stock thru-axle is not strong enough to haul your precious cargo! Our axles are 3 to 4 times stronger than the stock axle that came with your bike. Our stainless steel axle ends provide a safe and secure attachment point of the hitch to the axle. The axle is quick to install and remove with a common 5mm hex key.

Our axles are not just designed in the USA, but are made here as well. They are machined by avid cyclists to the tightest standards in the industry. We safety test, to failure, every batch of axles we produce to ensure they exceed your expectations.


Robert Axle for Kid Trailers replaces your stock thru-axle so you can attach a child or cargo trailer to your 12 mm thru axle equipped bike.

  • This axle is compatible with Burley, Carry Freedom, Chariot/Thule, Croozer, Instep, and many more hitch style trailers.
  • The true length of the axle shaft is 172 mm, but can be shortened using the included spacers – a flat 5 mm spacer and a tapered 5 mm X-12 spacer. This allows for axle lengths of 162, 167, or 172 mm. Please note: Thru-axle lengths do not equal hub standards. An axle has to be longer than the hub to fit in the frame. A 12×142(+) hub does not equal a 142mm long axle.
  • This axle has a 1.0 mm thread pitch.
  • The axle shaft and axle end are precision CNC machined.
  • The axle shaft is 7075 aluminum and hard black anodized for rugged durability.
  • The axle end is stainless steel, which allow for mounting of the hitch provided with your trailer. The threads are M10x1 (metric).
  • Hardware for attachment of the hitch is included; the hitch is not.
  • No special tools required. Design allows for installation or wheel removal using your standard 5mm hex wrench.
  • Designed, built and quality tested in the USA. Proven around the world.


Need more information about how our axles work?

55 reviews

  1. Doug

    Until I found this product, I was going to purchase a mtb I didn’t really like as much as the Specialized Camber 29er becuase I needed the ability pull my child trailer. This thru axle fit perfectly and felt sturdier than the original.

  2. Far North AK (verified owner)

    Awesome! Works on my Santa Cruz perfectly. Now I can go have fun on the single tracks and come back, put on the trailer and go out with my wife and daughter on the same bike! It rules!!!

  3. Kelly (verified owner)

    Works great! 10+ I can ride with my pup in the trailer any time now, on any bike! (My disc brakes and thru-axle were a challenge previously)

  4. Siso (verified owner)

    Works Great! +1

  5. Steve Fleck (verified owner)

    Great product! Really well made and works perfectly with my mountain bike. No need to bring a separate bike to tow the trailer anymore.

  6. Andrew Fuquay (verified owner)

    The axle fit perfectly on my Santa Cruz blur. Seems to be very strong. I’m able to hook up and disconnect my baby trailer without swapping axles. Just leave the Robert axle in and hit the trails after pulling my kid around town. This is a great solution for the over size thru axle problem for hooking up attachments. I spent a long time trying to figure out a way to hook up a trailer to my mtb’s, I’m super stoked to have finally found something like this. Thank you guys.

  7. Kurt (verified owner)

    This worked great for my bike. Very easy to install and use with a Thule Chariot Cougar. Just be careful to not overtighten, as it could be difficult to remove. I swap back to my stock axle for actual mountain bike rides.

  8. Pierrick (verified owner)

    Je suis super content !!!
    This worked great for my e-bike. It’s easy to install.
    I use it with my crooser chariot.
    Now I can travel with my daughter!!
    A french biker happy

  9. Justen (verified owner)

    I have a stump jumper soft tail that I love to ride but found myself taking my less desired backup bike to pull my youngest around in until I found this axle. It’s awesome I have found it mounts to literally every child trailer I have ever seen. Great product very well made, and shipping was fast. Thank you guys for making a great product.

  10. James (verified owner)

    Ordered this item for my wife’s new bike so she can tow our son to the park in the Burley Honey Bee trailer. Works and fits perfectly for this application with absolutely no issues. So glad I found Robert Axle Project. It saved us from buying a separate bike just to tow our son. Now she can enjoy an awesome bike for trail riding, AND tow our son for leisurely rides on the bike path on the same bike. Great product!

  11. Brett (verified owner)

    Amazing product and the engineering and design is fantastic quality! I ordered the wrong axle and the support team immediately helped me figure out the correct one and shipped it to me the next day. Installation was super easy and pulling my new Bob Trailer was so smooth and easy. Started training with the trailer for my first wilderness trek with a trailer and I have to say that every ride has been so smooth and solid thanks to this product! Well done guys and you have a fan for life!

  12. Alessandro Porrazzini (verified owner)

    Perfect!!! Very good fabric, good seller; fast delivery

  13. Victor Ing (verified owner)

    Glad I found this online and thank you for designing and manufacturing this much needed product!
    I tow my disabled adult son in a large special needs trailer. I now use my electric bike with this hitch mount thru-axle and know that the mount will hold up to the load. With over 80kg in tow, I now feel confident in the strength and quality of this product.
    Thank you!!

  14. Thomas D (verified owner)

    Works like a charm on my 2014 Stevens Jura Mountainbike. My son loves it to get to the Kindergarden by bike with his dad. Thanks for making this possible.

    • Katy

      That’s what we like to hear – biking to kindergarten. Thanks for sharing!

  15. Paul (verified owner)

    Amazing product, fits perfectly on my Santa Cruz 5010. I spent along time researching an axle that would work with my bike and thankfully The Robert Axle Project had one. Shipping was quick, even to Canada. I can now pull my son in his Thule bike trailer and I’m considering just leaving it in at all times so we can pull him whenever we want.

  16. Kristian Skjødt (verified owner)

    Axle is great. I had modifications made to my old trailer bracket but it did involve cosmetic damage to my frame. This one is super easy to mount, it’s very rigid, stays in place, and easy to switch around with other bikes.

  17. Denise and Michael (verified owner)

    The through axle was very easy to install on my Specialized Rumor and my husband’s Specialized Epic. We tow our Border Collie puppy to the park in his Burley Tail Wagon for some extra playtime. Makes for a very happy puppy! Now I have the ability to pull this trailer with every bike I own. Thank you for developing a product that meets our needs!

  18. UK buyer (verified owner)

    Have to say that the customer service from Chris at Robert Axle has been fantastic.

    Really helped out with an issue that I had, and made buying from the UK very easy.


  19. Stephen M. (verified owner)

    Application: 2016 YT Industries Capra pulling a 2016 Burley Bee.

    Website was very easy to navigate through for selecting the correct axle for my bike and trailer. Simply pick your bike and what trailer you’re using and it pops up.

    Installation was very easy and the product is very well made.

  20. JP Lewis (verified owner)

    Whip: 2016 Specialized Turbo Levo FSR – Charriot Cougar 2

    I got a quick reply on the verification of the axel type :: so that was cool.

    This axel is so awesome! We were able to haul our kids up a snowy road and hike into some Hot Pots in the Winter… blew our minds how this simple tool made it all possible to do such a grand trip with our kiddos in tow. Thank you!

  21. Le Corse (verified owner)

    Great product fitting perfectly my Stumpjumper, I received it faster than expected. I will highly recommend this product.

  22. David Sweeting

    Very happy- fits my stumpjumper and just works. Fast delivery as well all the way to NZ, thank you very much guys 🙂

  23. Hill (verified owner)

    Totally seamless fit between a Burley D’Lite and a Specialized. Happy with the entire buying experience and really thankful that the RAP is out there making these axles so that I can keep using my trailer with my new bike.

  24. Drew (verified owner)

    I was worried about it fitting my new bike with the X12 axle so I wrote them to see. Response was really fast and he gave me a link for the exact one to order. Click and ordered. Works fantastic for when I want to pull a kid trailer around the neighborhood on my $7k bike!…

  25. Paul Peterson

    Just installed this after having it delivered from Germany to Sweden!
    Works perfectly! Top notch product.
    Now we can resume the daily dargis (daycare) drop off.
    Except now it’s behind my new specialised turbo Levo, so are doing it in half the time!

  26. Karl (verified owner)

    I was so happy to find y’all’s axles. First time ordering I wasn’t sure I got the right size. The fit guide helped get the right axles for us (one for my wife, one for me). The axles are robust and well designed to fit a range of lengths, so clever. Y’all thought of everything. Five stars for y’all’s customer service too, you responded to my issue so fast and very kindly. My son loves going for rides now, and I am confident he’s safely in tow. Thank you.

  27. Nicholas Citriglia (verified owner)

    Worked on my 2016 Specialized FUSE! Kiddo loved Bar Harbor carriage trails. The axle fit perfectly and arrived super fast! Thanks for making this my family is very appreciative!

  28. Jorge Rodriguez (verified owner)

    This fits my 2012 Stumpjumper FSR perfectly. I would even say better than the original DT Swiss Through Axle. This is a perfect solution for what seemed to be an unsolvable problem; even my LBS told me there was no way to attach a trailer to my bike. Shipping was lightning quick and the support videos are comprehensive with installation instructions; follow the initial installation instructions, and it’s really easy to switch back and forth.The axle is really well made and exceptionally engineered. They’ve done an excellent job at designing such a simple, yet elegant solution.

  29. Tiffany (verified owner)

    My local bike shop recommended this part and it works as advertised. The sizing chart was spot on, installed with easy to follow instructions (I loath returning internet purchases that don’t work). Pulling a Burley kid trailer with a Specialized 29er and as a new parent I’m discovering a whole new world of gadgets. Would love to see your product at bike expos and local bike events — quality axel and user friendly website.

  30. Daniel (verified owner)

    great product that works with my Chariott and nice thing is with the included allow spacer it fits both my wifes Intense that is 142×12 and my boost bike. Know not case in all but this is great that the boost to non-boost spacer is included. Made our day and little one loves it!

  31. Mike (verified owner)

    Very pleasantly surprised how seamlessly this worked with my bike. I had a difficult time finding a thru axle for my mountain bike. But this one slipped right in and my little boy and I were on our way in no time. Very happy with the purchase.

  32. Paul (verified owner)

    Product far better than described and service is just simply first class! Easy to fit and once on its super easy to remove and use the original when not towing.

  33. pukki81

    Using this on my Canyon Spectral al 7ex with great results. Seems actually better than the stock axle that came with my bike. I can just leave it on the bike and use the kids trailer hitch when needed

  34. Ed (verified owner)

    The 12mm thru axle works perfectly on my Stumpjumper. It allows me to pull a Burley cargo trailer with no problems!

  35. Dan

    Works perfectly on my Specialized Epic. Great job guys!

  36. Doggie Traveller (verified owner)

    great product, easy to identify correct axle and fast delivery

  37. Hunter (verified owner)

    High quality product, easy to identify correct axle, quick support for any questions, and fast delivery.

    Awesome to be able to pull a trailer with a Specialized Turbo pedal assist bike!

  38. Miikka Nevalainen (verified owner)

    Perfect solution!

  39. A A Ron (verified owner)

    Solid product. I just like every other reviewer of this product found, purchased, and received everything I expected with this through axle. Quality craftsmanship, and the perfect component to allow me to enjoy time with my wife and children. (and six stuffed animals, and snacks, and wa wa, and a ba ba)
    Well done Robert Axle Project.

  40. Derek H (verified owner)

    Thank you for sending the axle quickly which arrived with good instructions and well packed. The axle is perfect for the trailer that tow behind my e-bike.

    Thank you again,


  41. Tim (verified owner)

    So happy to have found this resource. Super easy to indentify the correct axle and fast shipping. The product works perfectly.

  42. Angel (verified owner)

    It is an excellent quality shaft, it is perfect for my bike, Specilized Turbo Levo. The shipment was fast, I live in Spain. I definitely recommend it.

  43. Tom Lindsay (verified owner)

    Perfect fit, high-quality product with amazing post-purchase support!

  44. Tyler (verified owner)

    Purchased for my Specialized Fuse Comp 2018. Quick and easy install, works great with my Burly Bee. Axle is well made and instills confidence when you can compare it to the bikes existing axle. I have zero complaints and zero worries that I’d have any issues with this axle.

  45. Stian Rølvåg (verified owner)

    Bought this for mye Specialized Turbo Vado 3.0. It fits very well. Awesome product and delivery time.

  46. Jason in Arizona (verified owner)

    This is was a lucky find and an excellent piece of hardware. I haven’t bought a new bike in nearly fifteen years so the through-axle was something I had only seen on downhill bikes and was bummed when I realized my hand-me-down kid trailer wouldn’t attach. This is the missing piece we needed. It works well and feels super stable on my Specialized Sequoia.

  47. Michael Davies (verified owner)

    Fits great, easy to install (hold the axle with the allen while you tighten on the trailer yoke). Allows me to bring one bike on bike trips which is sweet because it is my only trick to get the baby to nap.

  48. Rodney Bosson

    Works fine – no problems fitting the axle – The trailer fits and have traveled over 200 miles since installing it three weeks ago. Can not speak highly enough of the service and the product. Fully recommend.

  49. Peter Henriksen (verified owner)

    Great product, very well made and fits perfectly. Excellent communication and very efficient service, it was delivered to me in NZ in less than 4 days!

  50. Maxime B (verified owner)

    Fonctionne vraiment très bien. Je recommande sans hésitation. Je trouve que tirer le chariot des enfants est beaucoup plus facile et stable avec le vélo de montagne que le vélo de route.

    It is perfect. Working really great with my MTB 12×144.
    I find it way more stable and easier to pedal the kid trailer with the MTB than the roadbike. I highly recommend the Robert Axle.

  51. Lukasz

    Superb! Better than original one! Fast shipping, recomend to everyone.

  52. Brandon Copley (verified owner)

    This solves my thru axle problems with my InStep Single Seat and Double Seat Foldable Tow Behind Bike Trailers. I can now run this trailer behind my carbon gravel bike without worrying about the frame. Love it!

  53. Gabriel (verified owner)

    Fits and works!
    Shipping overseas worked perfectly too.

  54. Kerry Anne Godbout (verified owner)

    Oh man! This axel SAVED our summer! I ride a Spec Chisel 29’er with a maxel and I was having a heck of a time finding the right axel to tow our Thule trailer. The axel finding feature on this site got it right, the shipping was fast, and the axel is a beautiful fit. I even forgot to take it off on a solo ride and it survived the pounding like a champ. Made a customer for life!!

  55. Vera Krsickova (verified owner)

    Great product, works perfectly with my eBike. Very fast oversees shipping. Thank you. Vera

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All orders from our website are via US Postal Service, from Oregon, U.S.A. We make every effort to ship your order within one business day.

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