Surly MDS/Gnot-Boost Thru-Axle for Kid Trailer – 12×142/148

(20 customer reviews)

$ 58.00

This axle is specific for Surly MDS or Gnot Boost bikes with 12×142 or 12×148 hub spacing.

The derailleur end of our axle is internally threaded and will use the bolt from your stock Surly axle. The disc brake side of our axle has a permanently attached mount that has an external M10x1 thread and includes the hardware to attach any kid trailer hitch to this axle.

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.

In stock

Get 20% Off Lightning Bolt-on Axles With Purchase of Any Trailer or Trainer Axle! Discount Automatically Applied.
SKU: KID218 Category:


This axle is compatible with Surly bikes that have the MDS or Gnot Boost axle system and 12×142 or 12×148 hub spacing.

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.

Prop65 Warning icon

WARNING: This product can expose you to chemicals including nickel acetate, which is known to the State of California to cause cancer. For more information, go to

Additional information

Weight 0.3125 lbs


Robert Axle for Surly MDS/Gnot-Boost bikes replaces your stock axle to attach your child trailer to your 12×142 or 12×148 thru-axle equipped bike.

  • This axle is specifically designed to fit the 142/148 hub standard Surly MDS or Gnot Boost bikes.
  • The derailleur end of our axle is internally threaded and will use the bolt from your stock Surly axle. The disc brake side of our axle has an engineered mount for your trailer hitch. That mount has been permanently attached to the axle.
  • This axle is compatible with Burley, Carry Freedom, Chariot/Thule, Croozer, Instep, and many more.
  • 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?

20 reviews for Surly MDS/Gnot-Boost Thru-Axle for Kid Trailer – 12×142/148

  1. Ted Forgeron (verified owner)

    This axle works perfectly with the new 2018 Surly Midnight Special Road Plus bike! I use it to pull a variety of Burley trailers (kid and cargo).

  2. Darin (verified owner)

    I ordered this axle for my MDS Karate Monkey to pull my Burly Bee trailer.

    The quality of the axle is impressive, and it bolted into my frame without any trouble.

    It is heavier than the stock Surly axle, but that’s reassuring when I’m pulling my kid in the trailer. It also feels much more secure than the quick release set up I was using before.

  3. Andrew (verified owner)

    Just what I needed for towing a Burley kid trailer behind my ’17 Surly Krampus. The axle provides plenty of clearance between the hitch and the dropout shoulders to run the axle anywhere along the horizontal dropout. I love that bolting the axle into the dropout and bolting the hitch to the axle are done with separate fasteners – huge improvement compared to the QR axle setup I was running on a different bike. Been using it daily for a few weeks now with zero issues.

  4. Josie Paruolo (verified owner)

    I have a Surly Karate Monkey and have pulled a burley child chariot for quite a few miles on bumpy dirt roads. Without this axle I don’t know what we would have done. It provides the clearance needed to attach the hitch provided by burley. Thank you so much! Couldn’t be happier with my purchase.

  5. Jakub @ Bikepacking Nomads (verified owner)

    Works perfect on my Surly Karate Monkey 2017! The price of the axle and the shipping to Czech republic is worth and also it reached us surprisingly fast! Thanks for that!

  6. Stephen Phillips (verified owner)

    So happy with this! Really filled a need for me. I have a Surly Midnight Special and wanted to be able to hook up a kid trailer. Without this I’m not sure how I would have done it. High-quality, nicely finished, fit perfectly.

  7. Jesus Pacheco (verified owner)

    Worked perfectly on my 2021 Krampus pulling an old Chariot Cougar double trailer.

  8. Ewan Nurse (verified owner)

    Easy to install, works great

  9. Mike (verified owner)

    Excellent product! Works really well with our double trailer. Easy to install and use.

  10. jonne reijonen (verified owner)

    Quick delivery to Finland and great extremely quick customer service provided, when I needed the invoice for customs clearance. Gret job and thanks!

  11. Mike Brown (verified owner)

    Great product, worked perfectly on my surly midnight special.

  12. Stan

    Works as advertised on my 2022 Surly Ghost Grappler towing a Chariot cx2. Good quality axle. Thanks.

  13. Bart (verified owner)

    Lighting fast shipping and the axle works like a charm, my 2023 Karate Monkey tows my Burly DLite anywhere I want. Off road, singletrack, grocery runs, anything is possible, so my son, my dog and myself are very happy customers!

  14. Jared (verified owner)

    Works great on my Surly Midnight Special pulling a Burley D‘lite X.

  15. Brian (verified owner)

    Works perfectly to fit Thule Chariot trailer on my Midnight Special, thank you!

  16. John

    This worked great with my 2022 Surly Ghost Grappler. I mounted the standard Burly hitch to it which works great. My wheel still turns! Along with the two I’m now pulling.

  17. Ryan (verified owner)

    Works perfect with my Surly Karate Monkey. Simple. Does exactly what its supposed to do.
    It is the axel only, you need to reuse the bolt for tightening the thru axel to the frame.

  18. Matt McCourtney (verified owner)

    Works Great on my Surly Krampus towing a kid trailer. Easy to install, simple to use…. Thanks for the solid product!

  19. Jeremy (verified owner)

    Bought this axle for a Karate Monkey to pull a Thule chariot. It is a perfect fit. Highly recommend going this route instead of finding a Thule axle for the same purpose.

  20. Anthony Whittley (verified owner)

    Outstanding customer service. Quickly answered my questions regarding fit. Shipping was fast. This axle fit perfectly on my Surly Skid Loader.

Add a review

Your email address will not be published. Required fields are marked *

You may also like…

  • Robert Axle Project Cycling socks by The Athletic

    Robert Axle Project Socks

    $ 20.00
    Select options
  • Thru axle for bike trainer axle-part-TRA003

    12mm Thru Axle for Trainer: Surly MDS and Gnot Boost

    $ 54.00
    Add to cart