How I Modified a Thule Bike Trailer Hitch for an E-Bike with a 12mm Axle10 Sep 2021
Thule makes several popular bike trailers, including the Cadence and Chariot. The trailers come with the Thule ezHitch to attach easily to most quick-release or solid axle wheels, and Thule also sells an adapter to make the ezHitch fit on thru-axle wheels. This covers most common bicycle setups, but it leaves out many e-bikes, which often use 12mm solid rear axles. And that’s really unfortunate because towing a trailer is a great way to use an e-bike! I figured out how to modify a Thule ezHitch to fit on my e-bike with a 12mm solid axle, and I’ll show you how I did it below.
The Thule ezHitch is compatible with most solid axle bicycles, but most solid axle bicycles use a 3/8” (~10mm) axle. Larger rear axles are common on e-bikes because many e-bike designs apply torque against the rear axle and therefore rely on a sturdy solid axle, often with additional measures (such as anti-spin washers) to prevent the axle from rotating against the frame. For example, my Juiced CrossCurrent e-bike has an M12x1.25 rear axle and some Rad Power Bikes also have a 12mm rear axle. Unfortunately, Thule doesn’t offer any adapter that will fit a 12mm axle, so Thule trailers are incompatible with many e-bikes – unless you modify the hitch to make it work!
Do this at your own risk!
The following is not officially supported by Thule. It will almost certainly void your warranty, and could result in serious injury or death. I'm not recommending that you do this or that it's safe to do; I'm just showing you what I did.
Well, if the hole on the Thule ezHitch is too small, the obvious solution is to make the hole a little bigger – and that’s actually pretty easy to do. You can drill through stainless steel using a cobalt drill bit and an ordinary drill. I picked up a 1/2” cobalt drill bit for about $25 at Home Depot. 1/2” is 12.7mm, so this is slightly larger than the axle – but 1/2” is a common drill bit size and the extra 0.7mm gives just a little extra room for error. When researching this idea, I found a YouTube video on the RadCity eBike Vlog that shows a similar approach for a different trailer brand - you could watch that if you want to see what to expect.
When drilling steel, you should go slower than you would if you were drilling wood. Running the drill slowly will reduce the amount of heat that builds up, which will reduce damage to the drill bit. It took several minutes of drilling for me to get through the layer of steel. While you might be able to use a drill bit that isn’t cobalt, it will probably damage the drill bit. My cobalt drill bit seems to have held up great!
When you’re done drilling, the project is finished. The whole thing only takes about 5 minutes and you’re ready to install the hitch on your e-bike! The axle on my Juiced CrossCurrent was long enough that the extra space for the hitch wasn’t a problem. My hitch now fits perfectly on my e-bike, and pulling my son around in the trailer is a blast! It’s really nice to have the extra power from the e-bike when pulling the trailer up a hill or travelling longer distances – the e-bike with a trailer is a great combo and I’m glad I found a solution to make my e-bike work with a Thule trailer!