My Cart



Global Shipping • Click & Collect • Same-day order despatch before 1pm • $12.95 Express Shipping*

MTB Suspension Sales, Service & Support

Trek Shock Upgrades - Thru Shaft to Standard

Posted on March 09 2023

Trek have long been at the forefront of proprietary suspension technology, along with other big brands such as Cannondale and Specialized. In this blog, we are hoping to help outline some of the compatibility confusion that arises when looking to upgrade from the OEM proprietary thru-shaft, or DRCV shocks that Trek have specced across many models since we can remember. In recent years, Trek have used a specific 230mm trunnion shock in their Remedy and Slash models, a size which would normally only be a standard eye to eye size. Ie, 230x57.5-65mm. Trek's main reasoning (we suspect) for this proprietary sizing is to allow for sufficient room to house both the thru-shaft technology found in the shock, as well as for reservoir clearance with the frame under full compression. The reservoir on Trek's proprietary 230mm Trunnion shocks sits much higher when compared to a standard 230mm shock in the same make and model. 


However, being a proprietary shock comes with its limitations and users will often find themselves looking for ways to improve performance, beyond what the standard shocks can offer. This is where Trek have accommodated the market demand by offering some models without the 'thru-shaft' shock as an example, and or offering conversion bolt kits to users with the 'thru-shaft' models, allowing them to upgrade to aftermarket shocks. The conversion allows for the use of modern air or coil shocks on frames that were originally specced with the OEM thru shaft shock. 


Trek's require a Trunnion to Pin adaptor when converting from a Thru-shaft shock, to a standard shock. The shock also requires standard Fox or Rockshox mounting hardware. As pictured, the shock on the left is the thru-shaft model, and the shock on the right is the standard model with Fox mounting hardware fitted. 



Trunnion to Pin adaptors come in a variety of options, and for simplicity we have gathered as much compatibility info as we can, to make your decision making easier. Here's a breakdown of what goes where. 



Commonly used for the upper + lower shock mounting bolt on Slash 17-20.  Upper shock mounting bolt for Slash 21+, Rail (2020+), Remedy (2019+), Fuel EX. Used in conjunction with either 50mm x 10mm (offset), 54mm x 10mm (with Trek 3mm spacer either side), or 60mm x 10mm mounting hardware. Trek Part # 540755 or 599898




    Commonly used for the lower shock mounting bolt on Slash (2021+), Fuel EX (2021+), and Trek Rail 2022+. Used in conjunction with 40mm x 10mm mounting hardware. Trek Part #5258210




    Commonly used for the lower shock mounting bolt on Fuel EX and Remedy and Slash (2017-2020). Used in conjunction with 50mm (49.78) mm x 10mm Offset mounting hardware. Trek Part #599899




    Commonly used for the lower shock mounting bolt on Trek Rail 2020/21,  Fuel EX Carbon (2017). Used in conjunction with 50mm (49.78) mm x 10mm Offset mounting hardware, or 40mm x 10mm hardware. Trek part # 540756 (16mm head for earlier frame), or 18mm head for later (2021+) frames. 



    Notice an error? Let us know!  

      Got a question?
      Send us an email and we'll respond as soon as possible. Contact us now