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I would like to purchase a trailer for my new bike. It is a Canyon Spectral:ON CF7 with a dropper post/telescopic saddle. My goal is to go shopping for groceries with my bike.

Now, I had a trailer for my older bike where you could simply attach it to the rear axle via a universal coupling link. However, since my new bike has a thru axle it’s not compatible any longer. I know that I could buy a thru axle with an adapter but since they cost as much as a new trailer I might as well get a whole new trailer.

I thought about a trailer where the arm attaches to the saddle post. However, I don’t know if this will potentially damage my new dropper post.

Does anyone have experience with trailers attached to a dropper post (on an e-bike)?

Edit: The setup looks like this (I will add a better quality picture ASAP): The rear of my bike seat clamp embedded in the frame

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  • I suppose you're not planning to attach it to the actual moving shaft of the dropper post? That would for sure be a bad idea. But if the fixed part of the dropper peeks out of the seatpost enough and you clamp to that, I don't see a reason why it would be more problematic than with a normal seatpost - after all, a dropper post needs to withstand the same force from the seat clamp as any other seatpost.
    – leftaroundabout
    Commented Apr 13 at 17:22
  • I also thought of your last point. I added a picture of my bike in the post above. I’m not sure if the clamp would be able to fit on the small part that is protruding since it is not smooth too. Thinking about it in a very pragmatic way: as long as I don’t touch the dropper post while the trailer is attached it should be fine to attach the clamp to the moving shaft wouldn’t it? Or would the force amplified by a certain lever arm then damage the inner mechanism?
    – eckh_ma
    Commented Apr 13 at 18:18
  • I definitely wouldn't risk that. - Does the Spectral not even have a seatpost clamp? Normally it's possible to just pull out the post a bit, to have space to clamp something on the outer post. (It means you wouldn't be able to use the whole travel of the post, but that would hardly matter for getting groceries...) Honestly, the whole idea of attaching a trailer to a full-sus mountainbike is a bit crazy - what might really make the most sense is to get a used commuter bike just for this purpose. You also wouldn't have to cry over that when it gets stolen while you're shopping.
    – leftaroundabout
    Commented Apr 13 at 20:23
  • I will inspect the assembly tomorrow. Thanks for the idea! Well, if someone would ask me about the best way to attach a trailer to a full sus mtb I would give them a strange look too. If I would get an extra bike just for shopping then a lot of advantages of my idea about comfortably getting groceries (without going by car) would vanish. Another e-bike is way too expensive and even an old bike is probably more expensive than just getting a thru axle adapter. Not to mention space. To me it’s still easier (assuming it works) to just attach a clamp to my bike every week and attach a trailer
    – eckh_ma
    Commented Apr 13 at 21:46
  • Do you have the trailer already? Or one in mind?
    – Criggie ♦
    Commented Apr 14 at 7:43

2 Answers 2

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Note there's a level of nuance here because most post-mounted trailer hitches have an element that bolts rigidly to the post, but not all of them. I've seen trailers (maybe all of them DIY) where the part that goes around the post is a loop of strong material that turns on it directly.

Never attach a trailer hitch of any kind to the telescoping part of a dropper. Anything on a dropper or suspension component that slides into something else is vulnerable to surface damage of any kind, like scratches, gouges, etc. Anything like that will interfere with the seals as it telescopes and perhaps damage them. Trailer hitches aren't trying to be gentle to the surface they clamp on, which you want smooth and even.

For the fixed part, there can be a tendency for significant unforeseen clamping forces to bind up the free movement of the dropper. Obviously it can handle a seatpost binder so there is probably a level where it's okay. If you had a hitch that doesn't clamp, that also might be okay.

The adapter thru axle is such a better solution it really isn't a conversation. That's the far more stable place for a trailer hitch to be anyway.

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If this is your only bike, and you have to tow with this, I'd have a close look at that second bolt which is above and forward of the Through Axle.

It might be part of the rear brake caliper support, or it may be a mountpoint for mudguards/fenders or even a rear parcel rack.

If the bolt is stout enough, it could work to hold a bracket which has the trailer's fastening/coupling.

A trailer does not apply a great deal of force when being towed.

I can't find a photo of the hitch mount I made for a coworker, but here's one off my bike:

enter image description here

(Additional photo to come in a couple of days)

I would personally be leery of taking a nice full-sus MTB to the shops and leaving it outside unattended. Even locked up they're still a desirable target for theft.

You mentioned an older trailer for an older bike - which sounds like a perfect description of a Shopper Bike if you still have them.

Also known as a Beater Bike it is something old, cheap, and perhaps ugly. You can leave it outside the shop with little concern for theft.

Save your nice bike for riding.

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    Thank you very much for your elaborate answer! Unfortunately, I think the bolt you are referring to is part of the suspension linkage/pivot system. I will borrow a trailer coupling from someone and see if I can pull out the dropper post a little so I can attach it. If that doesn't work I will prob. invest in a thru axle adapter since this is the option best fitting my use case. I know most people will consider this whole thing a war crime but I want to use my bike every day and for everything even when not riding trails and even when shopping groceries. It's fun and that's why I bought it :D
    – eckh_ma
    Commented Apr 14 at 16:51

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