Build a Trailer U-can pull with your bike (or small car)

Finished Photos 

Trailer Wiring

Another Option

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Click For Larger Image

At some point you've probably wondered to yourself....."self, I'd love to have a little extra space for hauling 'stuff' home from the swap meet or the outlet mall or for camping but trailers are sooooo expensive!  Is there a solution?" Well wonder no more because there is.

All you need is a light duty trailer (#42708 860 pound capacity) sold by Harbor Freight and your choice of car top carriers. You can order the trailer from the online catalog . Shipping (at this writing) is free and you'll only be charged tax if you live in California. If there's a Harbor Freight store in your area, you should still check the web page for possible sale pricing and the store will honor the web (catalog) price.

Before you buy, read through the following instructions and see if you really want to assemble your own trailer (it can be done in as little as an afternoon or weeks depending how much you want to put into the project)

Here's a photo montage of my project trailer:

In the upper left corner you'll see frame pieces hanging from my garage rafters. They're being painted black. You will need a minimum of two rattle cans of primer and two cans of enamel in the color of your choice. While you're at the hardware store, buy three cans of color. You can always take the extra can back. I used a single can of clear over the black. This is optional (and requires several extra hours of patience while the clear dries). The trailer out of the box is red. If that color works for you you'll save two days of cleaning, sanding, priming, painting and waiting for the enamel to dry (frustrating).

In the upper right corner you'll see the trailer kit bolted together. This is what you'll have out of the box. A frame, two wheels and a tongue. Note, after taking the picture I moved the center brace forward to the next set of holes (pre-drilled) in the frame to provide an extra 10" or so of tongue length. Others who've done this project report the extra length really makes a huge difference in the way the trailer handles behind a bike. It's far less sensitive to weight distribution and gives you some extra space to mount a cooler if you'd like. I also opted to clean the pre-lubricated wheel bearings thoroughly with solvent and re-pack with Mobil-1 Synthetic grease. Why? Because the lube in the bearings appears to be little more than Vaseline. Same color, same scent, same texture. You should really plan on repacking the bearings with a high quality grease. While you're working in the wheel area (preferably before you assemble the spring shackle) cut a piece of 1/2" ID auto heater hose (or garden hose) to fit inside the rear shackle and press the 1/2" bolt through the hose. This will cut down on some of the rattle made by the trailer as it goes over bumps. Another option (which I exercised) is removal of the smaller leaf spring. You'll be carrying less than half what the trailer is rated for and don't really need the extra stiffness. You might want to pull the trailer a bit with the spring in place then remove later if it's bouncing around a lot.

Middle left you'll see I chose to cover the frame with aluminum diamond plate. This not only stiffens the trailer frame but really looks terrific. I'm fortunate to have a metal supply outlet in the area that sells this stuff by the pound. a 48x48 sheet of .063 (1/16" thick) cost $32.00. This particular frame needs a 48x40 sheet and the cut cost another five bucks. Call it $40 and now the project is up to $179.00 (plus about $10 for paint if you elected to go that route). BTW attaching the aluminum (or whatever you choose to use) is easy and looks great using 1/4" stainless steel button head bolts with nylock (self locking) nuts.

Middle right you'll see I've mounted a Sears 20 Cubic Foot cargo box to the frame. There are plenty of other options out there. Prices range from $10 at garage sales to $200 plus for really fancy (and very well built) boxes. You could even build your own out of whatever materials you feel comfortable working with. Keep in mind the watch word for this particular project is "weight". We want as little as possible so you can haul more 'stuff' behind your bike. The cargo box pictured is the Sears X-Cargo 20 cubic foot model. On sale I got it for $159. Total cost for the project now has hit $338.00 but remember you can use other cargo boxes. I found 18 cubic foot units at Pep Boys for under 70 dollars. Keep it simple and the trailer plus a new box could total just over $200.

Bottom right you'll see I have used some light duty chain to keep the lid from falling all the way forward. This particular box has a couple of limiting latches that only allow the box to open about 30 degrees. It's tough getting stuff in and and out. I just drilled out the rivets holding those latches and, using 1/2 inch x 1/4 bolts, some S-hooks and chain set the lid up so it could be opened fully.  /files/includes/images/trailer_chain.jpg (48564 bytes) Cost, about $10 for chain and hardware.

Bottom left the trailer is ready for its maiden voyage, hitched (HitchDoc) to my Nomad. The trailer pulled great but the cargo box rattled a lot. That little problem was fixed with a roll of foam weather stripping which I ran around the lip in the lid. End of rattle. I still have some improvements in mind like using the left over diamond plate to trim the frame, maybe some baby moon hub caps and (those who know me would have guessed this first) some addtional lighting.   Speaking of which, it just won't do to have a bunch of naked wiring hanging out in public. /files/includes/images/trailer_tail.jpg (74087 bytes)

With my 80 pounds of camping gear plus 50 pound (loaded with food and ice) cooler, /files/includes/images/trailer_loaded.jpg (66835 bytes)  the trailer weighs 290 pounds. Within the 1/3 of loaded bike weight recommended by veteran trailer haulers and for around $200 (plus hitch) a huge bargain compared to most commercial trailer offerings.

Sweating Some Details

If you have a label maker (or know someone who does) it will help to have some information all in one spot like Trailer weight, tire pressure, lug nut torque etc. /files/includes/images/trailer_label.jpg (13332 bytes) (I know, blame the itty bitty buttons on the label maker for the wrong weight total.  It's fixed now)

Ready To Roll! (click thumbnails for larger images)

 Things I Have Learned:

1. 20 pounds of tire pressure works great. Sure the sidewall of the tire says 55 pounds but that is for maximum loading and you won't even be close. Here's how you determine pressure. Load the trailer as it would be for your trip. Pour some water in front of each tire and pull the trailer through the puddle. Note the wet tire tread. Too much pressure and just the center of the tire will be on the ground. Too little pressure and just the sides will be making heavy contact. What you want is nice even contact all the way across the tire. This will result in a much cooler running tire and even wear across the tread.

2. Turn the cooler around. Unless you have a positive latch of some sort on the cooler the lid is going to try to blow open (and will probably succeed) at highway speeds. Turn the cooler backward and this can't happen.

3. Never ever forget the trailer is back there. If you do you'll make a turn a little too sharp and pull the trailer wheel up over a curb (or you'll try). This is likely to pull your bike over if you have it leaned for the turn when the trailer suddenly stops. This should be top of mind whenever you pull in or out of a driveway.

4. Safety Chains: Adjust the length so they cross under the tongue (left to right, right to left) and so if anything happens the tongue will be cradled by the chain. You can check this by hooking up the chain and letting the tongue down behind the ball. If it its the ground the chain is too long.

5. Check everything every time you stop. It doesn't take long, just a quick walk around to be sure all your lighting is working properly. Your first few hundred miles after doing any wheel/tire maintenance you'll want to double check the lug nuts.

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Gettin' Hitched

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Closeup w Diamondplate

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Center Brake/Turn Light $4 @ Harbor Freight
(Note Capnuts In Top For Netting Eyebolts)

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Tongue Stand Is a WalMart Bicycle Side Stand $4 Bolts Through Existing Hole

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Trick Addition, It's a Swapmeet Cargo Net Attached To Lid With "S" Hooks & Eyebolts. As Lid Closes, Net Stretches Over Cargo Holding Everything In Place

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Floorboards Make A Great Cooler Rack
This Rack Is Made From a Cast Off Set of  Indian MC Floorboards (any brand will do) and a couple of pieces of 1/2" square aluminum tubing.   The tubing is notched in the center with an aluminum spacer in the slotted section to keep the bolts from crushing the tubing and add stability.   A solid bar of aluminum or steel would work as well.

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Now, If I Could Just Find a Black Cooler!  (fat chance)

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Ch Ch Ch Changes
Always tinkering, note the tongue has been extended 20" just by bolting in a 2"x2" solid aluminum bar (because it was handy).  The Cooler is now attached to the carrier using battery hold downs (big truck size) and the safety chains now have a hanger.   Oh, and the cooler is black thanks to Krylon "Fusion" paint for plastic.  Note: If your cooler doesn't have a very positive latch mechanism consider turning it around so it faces backward.  This will prevent the lid from flying open at highway speeds. (learn from my experiences).

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A closer look.  The chain hanger is just a 1/8" x 1" piece of aluminum notched to hold the chains up out of the dirt.  Extending the tongue allows more room for the cooler and places a lot less load (downward) on the hitch so you don't have to load the box so carefully.

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The top now opens sideways.  Why? The front opening makes one heck of a great sail in windy conditions.  The side opening is far more forgiving.  This was done with a simple 29" piano hinge riveted to the lid and side of the box.  The same chain used for the front opening was used here.

34 qt Ice Chest
Hinged Friction Fit Lid
Vented Food Tray (removable)
Refreeze Bottle Capable
12.763 x 21.457 x 13.474 in

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Hoppy model #46255 powered converter gets full power to the trailer lights and protects bike electrics at the same time.   Mine is mounted on the hitch with double sided tape. Harness shown on the right goes under the seat for all connections.  Harness from left side goes to a 4 pin plug for connection to the trailer.

See more information on trailer wiring below

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Another addition, diamond plate tool boxes and fenders

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A little extra space for tools, tent pegs, whatever

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Use piano hinge  and magnetic catches to secure lid

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Goodbye big ugly tail lights These are from Harbor Freight and have two bulbs each so one is used for running, outside bulbs are brake/turn

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Truck Box Liner keeps things in toolboxes from rattling


So, what do you need for this little project?

1- Harbor Freight #42708 48x40 single tongue trailer Normal price for this trailer is $189 but Harbor Freight ( or your local dealer) often put it on sale.   

Your choice of custom touches from Diamond Plate to lighting, the sky is the limit. But always be thinking "weight, weight, weight."

Now, go camping, go shopping just "GO". Once you've pulled a trailer behind your bike or small car you'll wonder why you didn't do it a long time ago.


Wiring the Trailer

Trailer wiring seems to perplex a lot of riders.  I think most of the problem is trying to figure out how to convert four lights on the back of the bike (turn/turn/brake/tail) to  (generally) two single bulb fixtures with a single two filament bulb in each on the trailer.  In other words how do you get one light bulb on each side to work as a brake light while it's also trying to flash as a turn signal and stay on as a running light at the same time. 

1. Add another fixture on each side for turn signals and wire direct from your bike wiring.  This works best if you're using LEDs for the trailer lighting due to the amount of power being pulled through the bike's wiring for the trailer lighting.  Wiring this way practically guarantees you'll have to uprate your tail/brake light fuse from (usually) 10 amps to 15 amps.  Doing that runs the risk of turning a weak spot in the bike's wiring harness into a fuse with potentially catastrophic results.

2. Use a simple non powered trailer converter.  Available at any auto supply or department store the converter connects on one side to the bike circuits for turn signals, brake and running light then automatically decides what filaments to run on the trailer so the dual filament bulbs on each side will run the appropriate set for braking turning and just rolling down the road.  The converters are really inexpensive, simple to connect but have a downside.  You're still pulling all the power needed for trailer lighting through the bike's wiring.  With the long wire run to the back of the trailer and if using incandescent bulbs the lighting tends to be dimmer than it would be if a whole 12 volts was getting back there.
3. Powered converter.  The Hoppy #46255 that I used fills the bill here.  There are probably other manufacturers.  The powered converter is really the 'safest' way to go.  It isolates your bike's wiring harness from the trailer completely and provides full power to the trailer lighting.  You 'still' connect one side of the powered converter to the bike wiring of course but the connection is only being used to send a signal to the converter.  Powered converters are a little harder to find in department stores but are plentiful on E-Bay and other online stores, even Amazon.
4. Use the relay system sold by Electrical Connection.  This is popular with Goldwing riders.  Using the relays (one for each of the lights) helps isolate the bike's wiring harness in case of a problem with the trailer.
After you've decided which system you prefer be sure you connect your wiring per the international color code.  Doing it that way assures you'll always be able to plug your trailer into any tow vehicle and you'll be able to hitch up any (suitable size) trailer to your bike without worrying about whether the lighting will work.  You'll find the code here.  The style plug you use will depend on the choice you're made above.  

Another Idea

/files/includes/images/rg_bike-trailer.jpg (209821 bytes)How about this option for those who don't really need a 'tub' to carry things around.   Rick Greif cut the Harbor Freight trailer down to 30" (tire center to center) and uses it to carry his 21 pound triathlon bike, a tent and other race gear.