Where to Find Longer Rear Axle for Pet Trailer?
 

I just bought an axle-mounted pet trailer made by PetSafe, but discovered that the rear spindle axle on my hardtail Trek is too short to attach the trailer hitch and safely close the quick release lever.

The existing axle is 180mm long. It appears I need an axle that's at least 200mm (7"+/-) long, preferably 210mm. Only I can't find an axle that size. I've searched everywhere it seems.

My question is: where can I get a longer rear spindle axle? Or is there another part that I would get instead? Any insight greatly appreciated. Thanks!

The trailer is almost certainly designed for use with a wheel with a nutted solid axle. Best solution would probably be to install such a wheel on the Trek.

Hmm. Do you have a link to an example of what you mean? Sorry I’m not too familiar with bike parts terminology. Thanks!

Examples of 26" wheels:

solid axle 26" rear bike wheel

Your wheels may or may not be 26" wheels. Your best bet would be to go to the shop where you bought the bike and ask them to order and install the solid-axle wheel. Assuming that the wheel is readily available (which it might not be, given the effects on the bike business of tariffs and COVID-19), the cost should be fairly low.

Ahh OK I see now, thanks. My existing wheel is 100 years old so replacing it is probably do-able. But is what you're saying that a longer QR axle just doesn't exist for this purpose? I see them for setting a bike on an indoor trainer, but am not sure if those longer axles are something that would work safely for a trailer setup.

Talk to the trailer manufacturer. That must be an issue that they get asked about on a regular basis. Otherwise, here you have 190mm. Next you can presumably make a longer axle out of a threaded rod. Finally, you can usually change the trailer hitch if the current one does not work. Trailer manufacturers usually sell different versions of their hitches, both the bike and trailer side, that can be combined with trailers manufactured by others.

OK, here is 210mm.

I don't know, I doubt it is as easy as getting any old super long skewer that can be found. Chances are good the proper skewer has some kind of proprietary hitch boss that the trailer hooks into. Skewers are sold by the OLD (overlocknutdimension) between the dropouts. Standard MTB is 135mm, Tandems are 145mm. Santana tandems are 160mm. I've never heard of a 200mm skewer. Not saying for sure there isn't such a thing but contacting the trailer manufacturer really is the best advice here. Something key is missing and I don't know what it is.
Edit: I've been to the PetSafe website and downloaded the installation manual for the pet trailer. To attach the hitch to a quick release wheel you undo the skewer put the hitch face on the outside of the non-drive side dropout and reassemble the skewer through the hole in the hitch head. You should not need an over-length skewer. If you think you need an over-length skewer then maybe you have the hitch head turned the wrong way. It's not that thick, 1/8th inch possibly? But if turned around the wrong way I can see how it might look like a longer skewer is necessary.