PDXTI is the brainchild and one-man crew of Eric Herboth, co-owner of RenCycles.com and worker at TiCycles.com. Eric is an enterprising fellow and noticed a void in the market for parts such as axle adapters, titanium headset spacers, headset caps and 3D printed parts. Thus, he decided to do something about it… but first, a little info about those other two companies Eric is involved with.

Ti Cycles Fabrication has been in business since 1990, and is renown for building anything you want in titanium or steel. Bespoke / Custom aka “Built In The Woods”, all of their frames are built in Portland, Oregon.

Ren Cycles draws on Ti Cycle’s 35+ years of fabricating experience to bring the virtues of premium materials and performance together, with the passion and practicality of everyday cycling. In a nutshell, Ren produces production frames and bikes at an attractive price point with options for customization.

One of the parts from Eric’s PDXTI operation is the 12mm to 15mm thru-axle adapter. If you own a bike or two, a wheelset or two, or if you’re like me and you review multiple bikes and wheelsets at any given time, you’re well aware of the different standards the bike industry has on offer.

In the world of thru-axle disc brake bikes, whether they be road, mountain, cyclocross or gravel, there are three standards that apply to the diameter of the axle itself. There is the 12mm thru-axle, the 15mm thru-axle, and the 20mm thru-axle, but we’ll be focusing here on the 12 and 15mm versions.

Generally, 15mm has been a mountain bike size, and with the development of disc brake for road bikes, 12mm has become the road standard. Gravel bikes seem to be a mix of both sizes, whereas most cyclocross bikes now utilize the 12mm standard (though many have also used 15mm). The trouble is, with two standards, it would be ideal if wheels between all bikes are universally compatible.

A lot of wheel companies make available different end caps or axles for both axle sizes, but not all. You can see where I’m going here…

Pictured above is Litespeed’s Carbon Gravel fork (link here to my Litespeed Ultimate G unboxing video), designed around the 12mm thru-axle size.

Because I’m always swapping wheels and tyres between the various review bikes I have going on, the different axle sizes have proven to be a real problem. I wanted a solution to this problem, but without always having to resort to a different send of axle end caps.

Before I go any further, this solution will only work on front wheels designed around the 15mm front thru-axle.

Review: PDXTI 12mm to 15mm Thru Axle Adapter - Simple solution to an annoying problemPictured above is a review wheelset, Industry Nine’s 700c TRA. The company supplied me with two sets of end caps for my review wheelset, but swapping end caps isn’t always conducive, especially if you don’t have a tool or the hand strength to remove the end caps.

Review: PDXTI 12mm to 15mm Thru Axle Adapter - Simple solution to an annoying problem
PDXTI carbon 12mm to 15mm thru-axle adapter and shop towel.

This is where PDXTI’s carbon 12mm to 15mm thru-axle adapter comes in handy. Weighing a paltry 9.7 grams, this simple tube of carbon fiber slides into your wheel’s 15mm front axle, spacing out the front axle and allowing you to utilize a 15mm thru-axle front wheel on a fork designed for 12mm.

Review: PDXTI 12mm to 15mm Thru Axle Adapter - Simple solution to an annoying problem

The PDXTI adapter is constructed from 3K precision rolled carbon fiber, measuring 15mm x 12mm x 99mm. It is slightly undersized by 1mm in width, to ensure an interference-free fit with many possible combinations of forks, hubs, etc.

It is important to note that there is a good chance this may not work with certain fork and hub combinations. Most 12 & 15mm end caps vary in outer diameter by about 2mm, which may cause interference with the fork “shelf” when inserting the wheel. But all of the combinations I’ve tried seem to work fine.


  • Apply a thin layer of grease to the PDXTI 12mm to 15mm thru-axle adapter, and your 12mm thru-axle.
Review: PDXTI 12mm to 15mm Thru Axle Adapter - Simple solution to an annoying problem
Litespeed gravel fork with DT Swiss 12mm thru-axle.
  • Slide the PDXTI 12mm to 15mm thru-axle adapter into your 15mm thru-axle hub.

Review: PDXTI 12mm to 15mm Thru Axle Adapter - Simple solution to an annoying problem

Review: PDXTI 12mm to 15mm Thru Axle Adapter - Simple solution to an annoying problem
PDXTI axle adapter installed and ready to go.
  • Install the wheel into your fork, then install your thru-axle.

Review: PDXTI 12mm to 15mm Thru Axle Adapter - Simple solution to an annoying problem

Go ride!

PDXTI’s simple solution to an annoying problem has proven noise and trouble free during my period of review. Because there is the risk of galvanic corrosion between a carbon tube and aluminium axle, I recommend you remove the wheel and axle adapter on a regular basis as part of your routine bicycle maintenance. Apply fresh grease if needed.

Review: PDXTI 12mm to 15mm Thru Axle Adapter - Simple solution to an annoying problem
Litespeed Ultimate G review bike.

PDXTI’s 12mm to 15mm carbon thru-axle adapter costs $US 19.00 and is available now.


Article and video by Gravel Cyclist. Jayson O’Mahoney is the Gravel Cyclist: A website about the Gravel Cycling Experience.


  1. Glad you to pointed out that this will not work for all.
    I have seen a handful of times of no-name hubs coming with 21mm O.D. end caps for 12TA and not fitting in the fork. SO a good idea for the consumer to measure the fork dropout shelf O.D. first before ordering something like this.
    (The 15TA end cap/drop out= 21mm O.D, 12TA end caps and fork= 19mm O.D.)

  2. I have one, and it’s quite nicely made (and fairly priced), but it hasn’t worked on any of my bikes because of the aforementioned fork “shelf”. Caveat emptor.

  3. Is there anything out there that would do the opposite? Make a 15mm fork compatible with 12mm hubs? I own a Santa Cruz Stigmata and have a nice pair of wheels with 12mm hubs that can’t be converted to 15mm… thanks

  4. How does this work on forks that are designed around 12mm TA and the standard 19mm catch flange? 15mm hubs have a 21mm catch…

  5. This type of adapter has been around for a while in metal. I have one from MTB Tools (mtbtools.com) that works with my Roval Trail SL front wheel on the fork of my Black Mountain MCD because the end caps on that wheel happen to measure 19mm. I was not able to use my wheel with SP dynamo hub on this bike because of its 21mm end caps.

  6. I was asking about this at a shop (which supposedly is one of the better ones in town), and they had no idea. The only solution they knew about is swapping end caps, never heard of a plug or shim that would do it.

  7. I use one to run XTR race wheels on my Devinci Hatchet. Works great, stays put in the hub when is swap wheels. I pretty much forgot about it until I saw this.

  8. A lot of dirt jumpers have 10mm horizontal drop outs, but finding 135x10mm thru axle rear hubs is tough these days. Options open up a bit with 135x12mm hubs.

    Turns out quadcopters use 12mm OD x 10mm ID tubing. Comes in both carbon and aluminum for cheap. Works like a charm.

  9. Glad you pointed out the galvanic corrosion possibility. It was the first thing that came to my mind.

    This product in aluminum or stainless steel would be great, I’ve thought about making my own. Weight penalty would be too great for many, maybe stainless and mill out a lot of material. But carbon is too great a liability in a high corrosive area like a hub. Maybe on a race day wheelset.

  10. Howdy. Thanks for all the comments.

    Mixed “standards” can be *REALLY* frustrating.
    In practice there are no standards in use for hub end caps or fork dropout pockets of any size, especially 12TA forks.

    For a wide range of 15TA hubs and 12TA forks this adapter is all that is needed to work together without issue.
    For a handful of other 15TA hubs (DT Swiss, Race Face, Mavic, Chris King) that are not compatible with all 12TA forks I have conversion kits available as well.
    No matter how you slice it some hub/fork combos will be really problematic but I’m always happy to help folks find a solution if possible.

    Dynamo hubs are an unfortunate outlier as the entire axle assembly is a fixed part of the dynamo and cannot be easily disassembled, and most of the 15TA dynamos have ~21mm OD axle ends.
    That said, lots of 12TA forks like REN GX1 and others will work great with the Shutter Precision 15TA dynamo hub, no problem.

    It is a frequent question but No, it is not possible to fit a 15mm axle into a 12TA hub.

    There are several aluminum versions of this adapter available that will surely work equally as well, though they are heavier and generally more expensive

    Modern aluminum hub parts are hard anodized, and with the recommended coating of grease on the axle/adapter there should be no issues with galvanic corrosion. All hubs still require routine cleaning and maintenance. 🙂

    Wholesale pricing is available for shops.

    Be safe, have fun, ride bikes!

  11. I had to put my end caps into a lathe (I have a wood lathe in my hobby shop) and turn down the tips to fit into my fork. My end caps are 21mm dia but the road fork has 19mm “catch flanges”. Took a few mins to turn the aluminum end cap tips down to 19mm, and they now fit great in my bike with the PDXTI adapter.

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