Originally Posted by Jamminatrix

The question is - how far do you want to tow and how fast? And what bike?

We have one for our Labrador (around 90lbs) for occasional Sunday afternoon rides to go down to the beach (maybe once a month). As a leisure thing it's fine, but I definitely would not advise doing any major rides on it (biggest reason is there's really no room for large dogs to get comfortable on these strollers).

Mine is basically a 2-kid trailer that I customized for my dog (all the dog specific trailers I saw were either way overpriced or undersized). I ripped out the kid seats and built a flat floor that sits on the frame, and used outdoor pool carpet on the floor to give some grip/padding for her paws when she gets wet from swimming. It still has the sides and back, and we just keep the top roof open (she's too tall and likes looking out anyway). It's typical 20'' wheels, 1.75'' tires, with galvanized tubular frame.

I never bothered to weigh the trailers, but I'd guess it's around 30lbs or so. Even with a 90lbs dog + 30lbs trailer, the added weight your bike is maybe 20-50lbs (depending how they shift their weight), because the trailer itself takes most of the load. The real hassle is towing and aerodynamics. It's basically like pulling a parachute behind you the entire time. I know for me personally (180lbs, 6'1''), if I seriously try pulling the trailer on my road bike, in full cycling gear, I will drop about 5-7mph for the same wattage as if I wasn't pulling the trailer. This is all flat ground.

I don't see both a 100lbs dog and 20lbs dog fitting the same trailer together comfortably without climbing on top of one another, but then again, it depends how patient they are. There's also a learning curve involved with the dog. It took some practice riding around out front to get her to learn to climb in/out and stay seated with the motion of moving. Our lab loves it, but our Chesapeake Retriever wants nothing to do with it (skiddish if there's no solid foundation that isn't moving).