Saturday, July 18, 2020

How to Carry a Bike With Another Bike

For years I’ve wanted to tow a bike with another bicycle and had this towing solution tucked away in my garage. Now I finally want to make it available to everyone! What do you do when you have one person and need to move two bikes? Maybe you’re taking a bike to be repaired, or your dirt jumper to the bike park, or picking up your friend at the train station and don’t want to drive there. Or you left your bike at the bar and need to pick it up the next morning. I searched all over and couldn’t find a solution that was compact, easy, and did not involve disassembling the second bike, so I designed my own device to tow one bike behind another.

Updated 4/21/2021

Attached bike ready to tow, thanks to my assistant


Assembled bike towing system ready to ride
Ready to go! And it won't fall over!

Some people online had elaborate contraptions with hinges, hitches, cages, and wells to hold onto the second bike, but I decided to take advantage of the fact that a bike already comes with a front end that has two perfectly situated sets of bearings (when holding the wheel, the wheel spins to allow up/down movement of the rest of the bike, and the headset rotates left/right so that the bike can trail behind) and also a rear wheel that spins and can carry the rest of the load. No need to have the whole bike off the ground, and no need to own a cargo bike!

Other bike towing systems not as good
I appreciate other people's creativity but I couldn't find an existing system that wasn't complex, required disassembly, or worked particularly well

The design I made is pretty simple but IT WORKS! I encourage you to get the parts to build one of these yourself, try it out, and then report back to me how it went, along with your ideas for improvement. I’ll keep updating the parts and designs here as I improve them over time.


How the towing system works

The front wheel of the trailing bike is lifted off the ground and onto a hook attached to the rear rack of the first bike. The wheel is secured in three places (three holding points will hold the wheel steadily in place) — on the hook, with a swing-out arm that attaches on the back side of the wheel near the downtube, and at a lower point on the wheel by the first bike’s chainstay.

Detail view of how the bikes attach together from the non-drive side
Detail view of how the bikes attach together from the non-drive side

Detail view of how the bikes attach together from the drive side
Detail view of how the bikes attach together from the drive side (bungee cord removed for clarity)

Actually towing a bike

  1. Place wheel onto hook on rear rack, cinch down strap
  2. Place lower part of wheel against strap on chainstay and cinch down. Note that it’s usually best to have that strap set back slightly (you’d have to push the wheel toward the rear) to improve foot clearance when pedaling
  3. Swing support arm over to rear side of wheel and cinch down.
  4. Attach a bungee cord from your rack around the head tube of the towed bike—this is the secret to not having the bike flop over when making tight turns!
That’s it! No need to disassemble any part of the bike. When not in use, the support arm swings around and can be attached to the top tube where it does not interfere with pedaling.

Where to attach the second bike to be towed

Detail view of bike towing system

Detail view of bike towing system

Detail view of bike towing system

Materials

I included sources for online purchases, though you would likely have luck with the small parts selection at your local hardware store for some of the regular hardware, and those come in very small packs. Note that some of the links are affiliate links (win-win, thanks for your support!).

ItemQuantity / NotesSources
U-Channel, aluminum, 1/2" high legs, 1-1/2" wide x 8ftNeed to cut two pieces: 12", 8"
The main structure
Grainger
McMaster
Wing Nuts, 1/4-28Need 3 from a pack
Something easy to tighten by hand, could also use a knob
Amazon
Grainger
McMaster
Female Rod End 1/4-28 x Male 1/4-28, right handed1x
This is the swivel joint
Amazon
Grainger
McMaster
Threaded Rod, 1/4-28 x 2 ft1x
Will be cut down to exact size, ~18"
Amazon
Grainger
McMaster
Socket Head Cap Screw, 1/4-28 x 1-1/4"Need 3 from a pack
Main connection between two rails
Amazon
Grainger
McMaster
Split Lock Washer, 1/4"Need 7 total from a pack
Used in multiple places
Amazon
Grainger
McMaster
Hex Nut, 1/4-28Need 5 from a pack
Used in multiple places
Amazon
Grainger
McMaster
Recycled Rubber, 1/8" Thick, 12"x12"1 sheet (need two pieces 1"x6")
Any thin rubber will do
Amazon
Grainger
McMaster
Bungee cord with hooks, 24"1x
Almost any will do
Amazon
Grainger
McMaster
Instamorph6 oz package or larger
Makes the two custom hooks
Amazon
Manufacturer
Voile Straps3x 16" nano or 20" regular straps work well. Depends on your tire/rim.Amazon
Manufacturer
Sugru moldable rubber1-2 packs of whatever color you like
This stuff is so useful!
Amazon
Manufacturer

Note on sourcing nuts/bolts/washers: Your local hardware store will likely have the common stuff in small bags for ~$1 which is perfect. Grainger and McMaster let you find exactly what you need and cost a little more, and Amazon is like the Wild West. I ended up getting most things from Grainger.

Note on bolt length: 1-1/4” length was good for me with a rack thickness of 10mm. Can make longer if your rack tubing is really thick or if you want to add washers to protect the aluminum channel.

Why use English thread sizes and not metric? Mostly because the only small ball joints I could find when getting started came in English fine-threaded sizes (I chose 1/4-28) so the rest of the hardware cascaded from that. That said, this M6 ball joint from McMaster should work and would allow all the hardware to be simplified to M6x1. If I was starting fresh, I'd use M6!

Tools needed

  • A drill for the 1/4" holes (same holes work for M6)
  • Wrenches for the 1/4" (or M6) nuts
  • Glue to attach the rubber to the aluminum channel, I used Gorilla Glue
  • Saw to cut the aluminum channel and threaded rod

Assembly

This is still an early version of the design so you might need to make slight modifications to be sure it will clamp correctly to your rack, etc. For example, confirm the width and height of the rails on your rack which can impact the spacing of the main mounting bolts and also how long you want those bolts to be. But the dimensions I have should work for most racks.

Shown here are Wrap-N-Straps, but I've since learned about Voile Straps which work much better.

Also please note that his is a hobby/DIY project and not a commercial product that has undergone rigorous testing. Use your head, make sure everything is mounted securely, and ride safely!

Bike tow system parts for assembly

Bike tow system parts for assembly

If there is demand I might start creating pre-made kits of these parts — let me know in the comments or email if you’d like that.

Tips

  1. Rack selection — I found that a sturdy rack like the Topeak Explorer MTX (REI, Amazon) holds a bike very steadily and doesn’t wobble back and forth like a previous cheapo rack I used (which eventually broke).
  2. Dealing with fenders — If the trailing bike has front fenders, try attaching the strap underneath the fenders to allow the wheel to move freely and not squish the fenders. On some bikes it’s probably fine to wrap around the fenders though.
So what do you think? Have you tried to solve this problem yourself? What worked and what didn’t? If you try building one of these devices please let me know in the comments!

Cheers,
Mike

20 comments :

  1. If you do make a kit available, I'm curious as to cost and postage to Atlanta, GA.

    ReplyDelete
    Replies
    1. Thanks for your interest! Yeah let's see how this all goes and I'll put some info up eventually if I go that way.

      Delete
  2. Thanks! I just tried this, slightly modified though as I don't have a bar to hold the handlebar. I used a bungee to hold the handlebar, but I see now why you use the bar, as the bungee pulls the bike forward.
    I'm going to try and replicate your setup in a slightly more lightweight manner, as I need to have a pannier on one side as well

    ReplyDelete
  3. This looks really great - thanks for the tips.

    Silly question - could this be simplified to just the top-rack and rear-triangle attachments if you used a clamp to firmly close the front brake of the trailing bike?

    ReplyDelete
    Replies
    1. Hi, good question. You could do that, but holding the wheel at only two points would be less stable. Holding the brake on loses the ability for the trailing bike to go nicely up and down over bumps, but it's worth a try to see exactly how it works!

      Delete
  4. Looks interesting but can you provide a close up picture of both bikes fully connected together? The video is too blurry to zoom in to see how the towed bike is fully attached. TIA.

    ReplyDelete
    Replies
    1. Timely question! I just received some new Voile Straps which worked really well for the assembly. I added some pictures with them, and they are orange for better visibility. Let me know what you think.

      Delete
    2. Perfect, now I see what's going on there. Thanks.
      One more question: when I saw the Voile straps, I thought velcro straps would also work. Do you think there would be any problems using velcro straps instead?

      Delete
    3. I've tried a variety of straps and so far the Voile ones work the best. Velcro can work I'm sure, but make it a design that cinches for the best chance of success. Let us know how it works out for you!

      Delete
  5. Can you give more detailed instructions on building this? It's hard to see the assembly from just the pictures.

    ReplyDelete
    Replies
    1. Sure, can you let me know what specific questions you have? Make sure to check out the two photos at the bottom of the post that show all the parts from the top and bottom, and there is the BOM, too.

      Delete
    2. I can't see the lower attachment part at all.

      Also I see all three contacts are on the front wheel. Does this create a problem with the towed bike being able to swivel while being towed?

      Delete
    3. The lower portion of the wheel is simply strapped to the chainstay, no special fixture. Are you asking about something else?

      The way the front wheel can move is actually ideal for this application — check out the second paragraph of the post. Also the video!

      Delete
  6. I would be very interested in a kit! I have quite a few friends here in the Twin Cities who also expressed interest, so if you don't make a kit, I may end up doing so.

    ReplyDelete
    Replies
    1. Ian, thanks for your interest! I’m working on a kit but don’t have a timeline. If you have a few people, would be totally reasonable for you to source the parts for the group. Let me know how it’s going!

      Delete
  7. What is the Sugru moldable rubber used for? I don't see any references to it outside of the parts table.

    ReplyDelete
    Replies
    1. Hi Ian, I used Sugru on the outside edges of the u-channel so that it wouldn’t scrat h whatever I leaned it against. I’ll clarify in the text thanks!

      Delete
  8. I’d be interested if you did have a kit :)

    ReplyDelete
  9. I have twin fifth graders and am tryna figure out how to bike them to school and then tow their bikes home with me. This seems bomber if I could have one on each side. Crazy? Any interest in suggesting mods to make this a doble?

    ReplyDelete
    Replies
    1. Very cool, Simone, and yes I've thought about this! Should be possible -- Both sides would need the hook to hang the front wheel, and both sides would also need the movable arm to come out and reach across to hold the opposite wheel. Certainly would have to lay it out to avoid interference between the two sets of handlebars and everything else. Can also customize for the slightly-smaller bikes of 10-year-olds.

      Go for it! Would love to hear about what you learn!

      Delete

If you're having trouble commenting with your google account, try enabling 3rd party cookies. In Safari, that means un-checking "prevent cross-site tracking" under privacy settings. Super annoying I know!

A Note on Affiliate Links

Please note that my site contains some affiliate links where I will earn a commission if you purchase the linked product. In 100% of the cases, these are for products/sites I have tried and/or own, or for books I have read. I do it for the learning experience and just for fun!