I’ve been trying to do more of my errands by bicycling, and one of my biggest holdups has been a lack of cargo room: it’s hard to lug home 80 pounds of cat litter in a backpack. So, a few months ago I started shopping on Craigslist for a bike trailer, only to find out that a good friend had one in her garage that I could have for free.
That’s a Schwinn (Pacific Cycle) Spirit Bicycle Trailer, rated to hold up to two 50-lb kids (aka: 100 pounds of cargo!). I immediately fell in love with it, and even used it to lug home 80 pounds of cat litter from the pet store:
An unexpected bonus of the trailer is that whenever I have it attached to my bike, cars give me more maneuvering room. I bike on city streets in Orange County, CA, and am used to having only a few inches of space between my side mirror and the cars zipping past me. But when I’m using the trailer, most cars will actually change lanes before even attempting to pass me (or at least give me four or five feet of clearance), and I’ve had multiple people literally stop to let me go in front of them. Amazing.
But using the trailer for cargo has proved to be less than ideal, as the bottom of the trailer is just made of soft fabric: the kids’ weight is designed to be supported entirely by the harness (which is hung from a horizontal metal rod). So, unless I had cargo that was perfectly sized to fit into that harness (like the bags of cat litter), I was limited to low weight.
So, I wanted to modify the trailer to add a solid base to convert it to a cargo trailer, and while I found lots of DIY tutorials, they all involved removing the fabric. However, I wanted to keep the fabric on my trailer to protect my cargo from weather and prevent it from blowing around. Additionally, my guess is that the extra space I’m getting when I use the trailer is due to both the visual bulk of the trailer (it’s actually the same width as my handlebars, but makes my bike look much wider) and also because people think there are cute wittle children in the trailer and thus are panicked about the possibility of hitting them1.
So, what I ended up doing is removing the harness and adding a wooden shelf that fit inside the existing fabric, so my trailer now looks like this:
Read on for full instructions on how I built this!
- Schwinn Spirit (model SC-821) bicycle trailer
- Wooden shelf: I used an IKEA Gorm shelf (20″ wide x 30.25″ long, with a 1″ rise built in; I had this on hand – you could probably just use a 1/2″ plywood board of the same size, though you might need a third riser)
- 3/4″ plywood risers: I used 2 1.5″x18″ and 2 1.75″x18″ plywood pieces as risers
- Fasteners: I used 6 1.5″ #10 self-drilling metal screws and four 2″ #12 wood screws.
- Wood finish: I used Behr Premium Transparent Deck/Fence/Siding Weatherproofing Wood finish (which I just happened to have on hand; use whatever you want)
Total weight added: 8 pounds (6.25 pounds for the shelf, 1.75 pounds for the risers), so the trailer’s rated cargo capacity is now 92 pounds.
- Tape measure
- Sabre saw
- Straightedge (to get straight cuts from the saw)
- Drill bits (sized for pilot holes for the screws, as well as a countersink bit)
- Sandpaper (60, 100, and 300 grit)
- Tack cloth (for finishing)
- Paintbrush (for finishing)
1. Remove the child harness: The harness was attached to the vertical rod that runs across the top of the trailer. I removed both of the screws that held the fabric in place, and also removed the latch at the end of the rod (it was just held in with a single screw), after which the harness just slid off. I then replaced the screws and latch. The lower part of the harness is just held in place by fabric straps, which I was able to easily thread out of the tent fabric.
This left the trailer as an empty shell. The front and rear 7/8″ square aluminum support rods are both perfect for supporting a base (the interior area is 24″ wide and 31.5″ long).
2. Overcome the problem of the lower fabric: As the trailer wasn’t designed to be a cargo trailer, the fabric that covers the bottom of the trailer comes up higher than the frame. Thus, if you were to try to put a platform directly on the frame, it would actually be resting on the fabric, not the frame.
Obviously one easy way to get around this problem would be to remove the fabric from the trailer surround, but I wanted to maintain the fabric. Since the fabric on the bottom of the trailer comes about 2" above the rails, I needed to add risers: I used two pieces of 3/4″ plywood on each side to raise the shelf 1.5″, thus allowing the shelf to fit inside the trailer without damaging the fabric.
Whatever type of board or cargo support you use, if you want to maintain the fabric of the trailer you’ll need to overcome this issue (and this obviously only applies to this model of trailer; I have no idea what other trailers are like).
3. Cut and pre-drill the risers: I used my sabre saw to cut a 3/4″ plywood board into 18″ long strips to act as risers. Unfortunately, the trailer’s rear reflector impinges on the back left side of the frame:
To account for this I cut a 1/2″ deep notch from the left side of two back risers. The reflector also meant that the shelf had to sit a smidgen farther forward on the back risers than the front, so the dimensions of the risers were this:
- Front risers: 1.5″ x 18″ x 3/4″
- Back risers: 1.75″ x 18″ x 3/4″ (with a cutout for the reflector)
I rounded all the edges of each riser with 60-grit sandpaper so there wouldn’t be any sharp bits that might damage the fabric. I then pre-drilled three countersunk pilot holes sized for the self-drilling metal screws in the bottom riser (I centered these on the aluminum frame, placing them in locations I knew I wouldn’t also want to use for the longer wood screws; test your assembly to be sure it’ll work).
Here’s what that rear riser looks like in place:
4. Finish the wood: I wanted to be sure the wood would be protected in rainstorms and when I was carrying liquid cargo, so I sanded it smooth (progressively using 100 grit and then 300 grit sandpaper), used tack cloth to remove any dust, and coated it with two coats of the weatherproofing finish (letting it dry for the recommended 72 hours). Here’s what everything looked like once it was finished:
5. Attach the first riser: I attached a single riser to the front and back frame, and then used this riser as a base that I’d attach the rest of the wood to. Before I did this I removed most of the fabric from the top of the frame (it just snapped off) to make assembly easier. Here’s the procedure:
6. Attach the second riser and shelf: I now used the first riser as the base to attach the rest of the wood to. Here’s how:
7. Reattach the fabric: Here’s a view of the trailer with the fabric mostly removed:
And here it is with the fabric reattached:
8. Admire: And that’s it!
To see more of my bike trailer pictures (do you really need to see more???), head to my of my DIY Bike Trailer Mod: converting a kid trailer to a cargo trailer! gallery.