I came up with this contraption for days when my kid needs a pick-up from school. He rides the bus to school, but on days when he has sport practice he misses the bus home.
I was inspired by this blog post which describes the idea of strapping the front wheel of one bike to the back of another. But my version uses a board with strap mount points that attaches to three MIK Side studs on the side of my rack using 3D-printed sockets.
The secret (that I learned from that blog post) is to make a tight strap connection from the head tube of the towed bike to the rack of the tow-er so that the towed bike doesn’t fall over sideways.
It seems pretty secure. But my bike wobbles continuously while towing. Not too badly, but enough to discourage me from making hand signals. I think maybe because the rear wheel of the towed bike is not in line with the wheels of the towing bike. Or maybe because the steerer tube of the towed bike is leaning a little to the right.
I’m thinking of trying another idea I read that would line up all the wheels: attach a spare hub to my rack, remove the front wheel of the towed bike, and use the axle to connect to the attached hub.
Good question! I did try that, and the setup was much less stable than with the rear wheel on the ground.
I think the issue comes down to a bike geometry concept called “trail”. Bikes are designed so that the contact patch of the front tire is behind the steering axis. If you look at a bike’s head tube, and draw an imaginary line straight out from that tube the line intersects the ground somewhere in front of the contact patch. That causes the bike to want to keep its front wheel pointed straight - the contact point tends to trail behind the steering axis like a shopping cart wheel that always flips around so that the wheel is always behind the axle that connects the wheel to the cart.
“Trail” is specifically the distance between the point where the steering axis intersects with the ground, and the contact patch. Some bikes have a large trail, and those are the most stable. Some have short trail, and have “responsive” or “twitchy” steering.
When I put the bike on backward the contact patch was in front of the steering axis so the bike wanted to flip its front wheel around backward, causing it to swing around wildly.
So how about if I proactively turned the front wheel backward? I don’t know - I don’t remember if I thought of that when I did the experiment!
Edit: How did “axis” become “access”? Wth autocorrect?
Interesting, thank you for the insightful reply. I guess when my car gets towed from the rear because it’s rear wheel drive it’s different because there are two wheels.