12mm Thru Axle for Trainer: 167mm with 1.75 Thread

(65 customer reviews)

$ 54.00

Our Trainer Axle is designed to adapt your thru axle equipped bike with your wheel-on trainer, such as a 1up, Blackburn, Cyclops, Kinetic, Tacx, Wahoo and many other trainers. Our goal is to fit the thru axle to your bike perfectly, so we minimize spacers and extra parts, providing a clean, high performance axle for your bike. Train, warm up and be race ready and fit for the season.

In stock

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SKU: TRA221 Category:


  • This Trainer Axle is designed to adapt your high quality bike to your wheel-on trainer. These are compatible with all the popular brands: 1up, Blackburn, Cyclops, Kinetic, Tacx, Wahoo and more.
  • Our first priority is building a precision thru-axle. Our axles fit into your bike as well or better than the stock thru axle.
  • The axle is installed with a simple 5 mm hex/allen key. The same tool that you carry on every ride.
  • The best part? When it’s time for your race or time to head outside, simply remove your bike from the trainer, remove the drive side axle end and go. Our axle is suitable for use on or off the trainer. Indoors or out.
  • Important: Before you order, make sure your specific trainer will accommodate the width of your modern thru-axle equipped bike. Measure your trainer at the widest setting and measure the outside width of your bike frame. The trainer axle ends will extend 15 mm past your frame on each side.


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 www.P65Warnings.ca.gov.

Additional information

Weight 0.3125 lbs


Robert Axle for Trainers replaces your stock 12 mm thru axle so you can use your bike on a trainer.

  • This axle is compatible with 1up, Blackburn, Cyclops, Kinetic, Tacx, Wahoo and many other wheel-on resistance trainers.
  • The true length of the axle shaft is 167 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 142 mm long axle.
  • This axle has a 1.75 mm thread pitch.
  • The axle shaft and axle ends are precision CNC machined from 7075 aluminum, and hard anodized for rugged durability.
  • No special tools required. Design allows for installation or wheel removal using your standard 5 mm hex wrench.
  • Designed, built and quality tested in the USA. Proven around the world.


Need more information about how our axles work?

65 reviews for 12mm Thru Axle for Trainer: 167mm with 1.75 Thread

  1. Brandon H (verified owner)

    This was the only axle that fit into an older compu-trainer my cycling coach is using because all other axles stick out too far on either side of the bike. After following the sizing guides, this axle perfectly fit my Trek Domane SL8. It is very good quality, fits the trainer perfectly, looks great, and was shipped very quickly. I’m very happy with my purchase and would definitely recommend this to others.

  2. Bill (verified owner)

    Proper axle fit, excellent service and shipping. Will use again.

  3. Antonio B (verified owner)

    Very good product and well finished.
    I used it to install my Trek Emonda 2019 on Tacx Vortex. Shipped in few days in Italy. Very satisfied!
    Thanks a lot!

  4. Levi Hill (verified owner)

    This was a gift for my father. Perfect fit, excellent service, speedy shipping. Love the axel finder feature.

  5. Esteban (verified owner)

    Whas exactly what I need. very good product. I will install in my Trek Checkpoint 4L. thank you very much!

  6. Mike (verified owner)

    Mounted a 2019 Norco x6 on an old cycle ops fluid trainer. Axle fits really well, some concern about environmental seal for outdoor use due to the inset nature of axel access on the Norco frame. It seems to work well on the trainer but will switch back to manufacturers’ axle for outdoor rides.

  7. Jeffrey Roger (verified owner)

    Hey, Hey, Hey!!!!

    This is the through axle trainer adapter you have been looking for.

    I too am riding a Computrainer and a Trek Domane SL7 with disc brakes and Ultra Di2 11 speed and after jerry-rigging a solution for 2 weeks I heard about teh Rober Axle Project from a friend in Bend.

    It arrived 3 days after ordering it and it took about 3 minutes to get it set up and m indoor training has never been better.

    I broke the frame from my Domane 5.9 in the Computrainer from the previous clamp on QR attachment. The Through axle puts so much less stress on teh rear dropouts (if any) and I am in Zwift heaven.

    Thanks tons!


  8. Jonathan B (verified owner)

    Ordered this axle for my 2019 Trek Emonda after getting an old Cyclops Fluid2. Axle finder made it easy to find exactly what I was looking for. Excellent service and shipping. Axle fit perfectly in bike and in trainer. Hopefully I won’t need a new axle for a long time, but definitely will be coming back here when I do.

  9. Ben (verified owner)

    Installed on a 2019 Trek Emonda SL6 for my Kinetic Road Machine, works great!

  10. Matt (verified owner)

    Purchased after getting a badly fitting axle from Amazon..promptly returned. The axle from RAP is a perfect fit for my Trek 2020 Émonda SL5 Disc. Precisely engineered, sturdy enough to leave in whether on/off the trainer, and very rapid shipping.

  11. Mark Werner (verified owner)

    Absolutely thrilled with this company and the product. I wanted a quality thru-axle at a fair price in order to use my Trek FX 5 Sport on my wheel-on trainer. I looked at the kit from my trainer manufacturer, but you couldn’t leave their axle in all the time. Seriously? If it rains one day and then is beautiful out the next, I don’t want to have to constantly swap out the axle depending on whether I’m riding on the trainer or outside.
    The fit, form and function of the product is excellent and having the axle finder tool on the site gave me confidence I was purchasing the right product. A complete home run!

  12. John V (verified owner)

    Worked well to fit my wife’s new Domane onto our old 1UP trainer. Well made, great fit, arrived quickly.

  13. Jahir Hussein Mohd Haniff (verified owner)

    2nd time ordering an axle from them. Top rated and highly recommended for your axle needs Specs are well detailed during the order process ensuring you buy the correct axle.
    Item was shipped almost immediately upon ordering and received 3days later in Singapore.
    Nothing but praises for the way you conduct your business. Well done , keep it up.
    I am a FAN!

  14. Russ (verified owner)

    The only word to describe this axle is PERFECT. Other products (which cost about the same) are made to fit a variety of threads and lengths which suits them but not me. I only have one bike that I will be using this on. And that added versatility in the other products makes it more challenging to take off and put on when I want to pull my bike off of the trainer and ride outdoors. No thanks. I’ll take the Robert Axle Project. Perfect fit and easy to take off and put on when I want to go outside. And I only do that because I have a dedicated wheel and tire for use on the trainer. If I didn’t, I could just leave it on. Rock solid.

  15. Kelan (verified owner)

    Perfect. Exactly what I needed to get my Trek Madone on the trainer.

  16. Bart Tate (verified owner)

    I searched and searched for a way to put my Madone on an old trainer (non-smart). Found RAP but was still a bit skeptical. However, these guys have it figured out and I now know they’ve done their homework. This axel works beautifully. Although I hate riding indoors this has allowed me to get 5 rides in already and will let me stay in shape over the winter/dark after work months. Thanks guys for figuring this out and allowing us who could afford the bike but can’t afford the smart trainer to go with it to keep cycling in winter. Love my axel!!

  17. Andrew L Harmon (verified owner)

    Fits absolutely perfect on my Trek Checkpoint AL4 and my Wahoo Kikr Snap! Fast shipping and great product.

  18. Rob Lisy (verified owner)

    Perfect. No problems, fit on the first try, easy to install.

  19. Andreas Reininger

    I was very happy to find the Axle Finder. And even more happy that my bike was listed. Then the happiness was topped when I received the axle. It fits perfect for my Tacx Trainer in combination with the Domane SLR7.
    For newbies like me I summed up my experience on my blog:

  20. Jim DeSalvio (verified owner)

    These folks know what they are doing. Perfect solution for conventional wheel on trainers for your bikes with thru axles. Great service AND, made in the USA!!! Buy with total confidence.

  21. Tyler Goff (verified owner)

    This is a far better product for the same cost as the saris universal through adapter. It fits perfectly and doesn’t come loose and it makes loading my bike into my saris fluid 2 much easier. I wish I wouldn’t have even wasted my time with the other one

  22. Will (verified owner)

    I was bummed when my new bike didn’t fit into my old trainer die to its thru axle…thanks to my new Robertaxleproject axle, I’m in business! The copious amount of helpful sizing information gave me confidence in placing my order. The axle arrived quickly and fit perfectly! The price and quality were a great combination. I will be referring my friends to you!

  23. Barry (verified owner)

    The axle is a perfect fit on my 2021 Domane SL5. I had been using another brand but could not use it to ride on the roads. This axle allows you to ride on the roads without having to change out the axle and is much easier to get the bike on and off the trainer. I still don’t know why they say you have to remove the drive-side piece before riding on the road because it doesn’t interfere with anything. Maybe to keep from losing it if it comes loose. I used a little Loctite on mine so that won’t happen. The only thing I would have liked to seen was an option to purchase a completely black version.

  24. Pedro

    Like a champ. 5min up and running.
    Fit perfectly

  25. Jason (verified owner)

    The TRA221 fits perfectly to mount my 2021 Trek Domane to my Saris (previously CycleOps) M2 trainer. Eliminates the concerns I had with the stock ‘generic’ thru-axle adapter’s non drive side threads contacting the dropouts.

    Trainer manufacturers should just send customers to Robert Axle Project instead of selling their own thru-axles.

  26. Mike O (verified owner)

    Trek Domane SL6. Perfect fit. The Robert Axle Project took all the difficulty out of finding a matching diameter and thread; you just tell them your bike and they send you the right part!

  27. Darryl Zwolinski (verified owner)

    Axel worked perfect for my Kinetic trainer and Trek Domane SL5. Was able to drop it in and tighten with no contact to frame.

  28. Biswaksen (verified owner)

    I recently got this axle for my 2021 Trek Domane AL3 Disc to run on a Wahoo KICKER SNAP trainer. Fits perfectly and works like a charm!
    Extremely happy with the product!

  29. Brittany (verified owner)

    This was exactly what I needed for my 2021 Trek Domane SL6 in order to use my trainer. Good quality and easy to install!

  30. Dan (verified owner)

    Perfect fit for my bike

  31. Gerard (verified owner)

    Excellent product. Works perfectly with my 2021 Trek Domane AL 2 Disc. Fits perfect with my Saris M2. Customer support was excellent. When my package didn’t arrive after the tracking showed it was delivered they were more than accomodating, and fortunately, the package arrived after a day or so.

  32. Reed Jackson (verified owner)

    2021 Domane and an on tire trainer. 2014 Tacx Vortex Smart. This axle saved me about $1000 on a modern direct drive. Someday I’ll get one but then I can’t n+1 in the bike stable. The axle is “Apple, Inc.” finish and quality. Thanks Robert Axle Project. Must be nice to solve nagging compatibility problems for a living. Nice work.

  33. steve (verified owner)

    Got this for my new Saris trainer… exactly what I needed and super fast delivery… I was quite happy to get it and get it on my new bike/trainer, got it on quick and easy, perfect fit for my Trek Emonda. Will definitely recommend it if given the chance.

  34. Montana H (verified owner)

    I ordered this axle after battling it out with my trainer for about a year. I had no idea this was the solution to constant slipping and ruining the paint on my frame. I quickly ordered this in the hopes that it would be the right one and work for my needs. It exceeded all expectations! It shipped INTERNATIONALLY within a few days (even though our borders are closed and US products are taking forever to get here) and fit perfectly and is of great quality. Would recommend to anyone!

  35. DarcyM (verified owner)

    Had a shipping issue on my end. RobertAxleProject made it right even though they had no obligation. RAP = FNA!

  36. Ken Harrison (verified owner)

    I am very pleased with my Robert Axle adapter for my thru axle that allowed me to use my bike on a Wahoo Trainer. Their instructions for measuring the axel were simple. It shipped very fast and I highly recommend them.
    Ken H

  37. John B (verified owner)

    Perfect design for solving a new problem for this first-time thru axle rider. Worked better than the solution provided by the trainer manufacturer for a higher price. Well-engineered and precision manufactured. I use the trainer axle as my regular axle for both indoor and outdoor riding. Thanks for making this a simple problem to solve.

  38. Len Zaikoski (verified owner)

    The “axle finder” brought me right to this one for my 2018 Trek Domane ALR 5 I wanted to put on my CycleOps Fluid2 trainer.

    Ordering was easy and delivery was fast.

    The axle fit perfectly and I’ve been using it for all of my outdoor rides with 0 issues.

    I’ve only put my Domane on the trainer twice so far, but both times the axle worked flawlessly.

    Excellent product!

  39. Markku A (verified owner)

    Very impressed with this axle to use on my Kickr Snap trainer. Originally, I purchased the Wahoo adapter and found that it was not very well made and hard to set up. This axle from Robert Axle Project was so much better and so easy to use. Totally recommend this!

  40. Tom (verified owner)

    Ordered this for 2022 Trek Domane. Axle for perfect with washer on end. Yahoo Kickr Snap is back in business with this through axle. Highly recommended

  41. JH (verified owner)

    A great axle that allows me to use my Domane in the trainer. Outstanding quality and highly recommend.

  42. Mike R (verified owner)

    Bought a new Trek Checkpoint and a Saris fluid 2 trainer for it. This is the only place I found that made axels for my bike and the trainer. Bought one for the same price I would’ve spent with saris if their axel would’ve worked. Received it in less than a week and have been riding with it for over a month with no problems at all! Nice tight fit. Threaded right in with no adjustments or modifications needed! Feels sturdy and smooth and more importantly it solved the last hurdle to get riding my bike inside!

  43. Kiersten (verified owner)

    This is a great product! I bought a Trek Domane 3, only to find out it was on a list of incompatible products with the Wahoo KICKR Snap. Did some research and found this Thru-Axel. It fit perfectly and operates exactly as I would hope with my KICKR! Would highly recommend leveraging their customer support, as they are great!

  44. Sydney Dunnill

    I ordered from Canada and my thru axle was shipped and delivered in only 2 days! The axle finder was really helpful to find the right size I needed and was the only website that supplied the size I needed for my bike. The thru axle fit perfectly into my bike and I can’t wait to use my road bike for training on my trainer!

  45. Jayne (verified owner)

    Used with 2021 Trek Domane AL3 Disc and SNAP kickr – works like a charm!

  46. Anne (verified owner)

    Got this axle to use on my “new” 2019 Trek Domane SL6 with my Wahoo Kickr Snap. It fits perfectly and I’ve already recommended the Robert Axle Project to two other friends who recently got a trainer. I was happy they asked questions to double check my bike make/model to ensure it was the correct axle before shipping.

  47. Adam turner

    Ordered this to connect my Trek Al domane 3 to my wahoo kickr snap trainer, fits absolutely perfect. Arrived to ireland in 2 days! Price is pretty expensive but regarding shipping etc this is much worth it.

  48. Allie (verified owner)

    I have a 2018 Trek Domane ALR bike that wouldn’t fit the WAHOO snap kickr due to the original axle skewer. I answered the prompts on this website which helped a lot. The axle that was sent fit perfectly with no problems at all. Robert Axle Project turned a headache into an easy fix.

  49. Tanner

    I purchased a Wahoo wheel on trainer before realizing there was an incompatibility with my Trek Domane SL5. After doing some research I came across the RAP axle, and placed my order. I’ve put a couple hundred miles on the trainer with the new axle and everything works perfectly. The axle came with everything required, it is extremely well made, and it came very quickly. Instructions were simple and effective, anybody could swap out their axle. I highly recommend if you have a need for a new axle!

  50. Tuncay

    Perfect fit for Trek Domane AL3 & Wahoo Kickr Snap. I’ve ordered from Ireland and it arrived before the items I’ve ordered the same day from domestic vendors.

  51. Marc G

    Really pleased with The Robert Axle Project. The site’s axel finder feature guided me straight to the exact thru-axle I needed for my bike to match my trainer, making a tricky process pleasantly simple. Delivery was prompt and the axle fitted like a dream. Thank you!

  52. James Cayton

    Super fast shipping and an outstanding product. I was looking for something that would work with my new wahoo snap trainer and although wahoo offers a thru axle kit you have 3 choices in that kit and are stuck with 2 axles that you can’t use-this was perfect you select what you want it for and you select t your bike and bam it’s all so w for you. You get a high quality product that works great without having to buy a special piece for your trainer to work

  53. Unkljimmy (verified owner)

    Perfect well designed product.Have Trek FX-5 and Saris Fluid ll Smart Trainer. Purchased the RAP axle perfect fit and no plastic spacers needed.
    This is exactly what u need u will not be disappointed

  54. Shawn Fillinger

    The axle didn’t work for me but through no fault of Robert Axle and more of an issue with my Canyon bike. They were great about trying to help me fix the problem and then ultimately refunding my money plus the shipping. Great company! Great customer service!!!!!

  55. Nicholas Daras (verified owner)

    This axle saved my life. I am new to the world of cycling and I purchased a Wahoo Kickr Snap 2 without knowing that it was incompatible with the through axle of my Trek Emonda SL5 (2019). After having a mild panic attack for a week I stumbled upon this incredible project and within a week the axle was shipped all the way to me in South Africa and it worked a treat! Thank you so much for this project!

  56. Andrew (verified owner)

    I ride with the new axeloften and works great on my trainer.

  57. GrooverMcTube (verified owner)

    I bought a Sportneer Trainer from Costco and tried to fit the skewer that came with it on my Trek Domane AL5. The skewer didn’t fit and I buggered up the paint trying to make it work. Then I learned about the Robert Axle Project thru axle (12 mm x 167mm x 1.75). Fit perfectly. The Sportneer is inexpensive but works well and is dead quiet (except for the noise of the drive train/chain)

    I’m kinda lazy so I’m going to leave the thru axle and the end cap on my bike permanently. That way I won’t have to monkey with swapping out the axle every time I want to use the trainer. I’m also kinda spacey so I’d probably forget to take the end cap out…

    Thanks guys!

  58. Alexander (verified owner)

    Axle fits really well. Amazing service. Received it in UK just in 2 days. Thank you!

  59. Steve V (verified owner)

    Website was easy to use to get the correct thru axle for a 2017 Trek Domane. The product shipped and arrived quickly and works well on my old Minoura Magturbo magnetic trainer. I was lucky to find this site!

  60. Peter (verified owner)

    Had my 9year old Trek SL5 stollen. Bought a current SL6 with thru axle which won’t fit my cycle ops trainer. The mechanic at Freewheeling Bike shop recommended The Robert Axel Project.
    Really easy to put your bike specs in to the website to make sure you have the correct part! Thru axle was well built and greased for easy installation. Works perfect with my cycleops trainer. Arrived quickly.

  61. Rob (verified owner)

    Exactly what I needed, this Thru Axle fit my 2021 Trek Domane SL-5 perfectly and has allowed me to use my Garmin TACX trainer without issue. I would highly recommend this Thru Axle if you need one so you can use a similar trainer. Now to get some miles in.

  62. claire (verified owner)

    after struggling to find the right axle for my bike/trainer combination, i was so relieved to find this site! axle arrived promptly and works perfectly with my trek emonda and cycleops trainer.

  63. Jeff Waneka (verified owner)

    This axel worked perfectly on my 2023 Trek Emonda and my ten year old Fluid Trainer.

  64. wes (verified owner)

    I ride a 2021 Trek Domane SL-6. I needed a new thru axle to link up to my dummy trainer.
    This axle was super easy to use. Right out of the box and onto my bicycle. No issues whatsoever. Out of the box and on the bike and riding in less than five minutes. These guys have a totally legitimate product.

  65. John (verified owner)

    Great quality great fit. Thank you for making these!

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