Introduction: Modify Bike Racks for Fat Tire and Tandem Bikes

About: Scientist, photographer, writer, cyclist, tinkerer.

Unconventional bicycles can be a lot of fun, but transporting them can be a hassle because they may not fit a standard bike rack. Specialized bike carriers can be expensive (tandem carrier >$400). In any case, this instructable will demonstrate how I modified various car racks to carry a fat tire bike and a tandem.


Tandem carrier

Tray Hitch type bike rack similar to this one:

Box tubing the same size as the rack support bars

Welder (optional; bolts can be substituted)

Angle grinder (optional)

Air die grinder (optional)

Black paint

Fat tire bike carrier

Roof rack similar to Yakima Frontloader:

Electric drill and drill bits

Bolts, lock washers and nuts

Rubber tarp strap

Short nylon strap

Step 1: Tandem Carrier

I purchased the tray hitch rack at an auction for $5. I never used it and it sat in the shed for a couple of years until my daughter and son-in-law got a tandem bike. They had no means to transport the big bike, so my thoughts turned to modifying the old hitch rack to make it long enough to accommodate the greater length of a tandem.

My plan was to add some tubing to each side of the support bar. This rack holds two bikes, and it made the most sense to convert the outer (more rearward) tray to hold the tandem, as that would be the easiest to load it on. The inner tray could still be used for an additional conventional bike. I removed the wheel holders from the outer tray using a standard box-end wrench. I found some box tubing of the same size as the rack in one of my piles of scrap metal. The tubing came from two posts from an old bolt-together wrought-iron fence. I removed the ends of the posts but saved the top caps. The support bar was about 5 feet long, and the tandem was about 8 feet long. Hence, I needed to add about 3 feet to the bar. There were some holes in the posts from the fence rails, but since I only needed about 2 feet of each one, I cut the centers of the posts out with a chop saw to make unholy pieces (a hack saw would have sufficed). I ground the metal burrs off the ends with a bench grinder. I had planned for 6 inches of overlap between the extension and the original support bar to weld, which should make for a more than adequately strong connection.

I prepared for welding by sanding the edges where the pieces would adjoin over their 6-inch overlap. I used an air die grinder on the rack and a bench-top wire wheel buffer on the extensions (both were powder coated), but sand paper would work. I removed the plastic end caps from the rack and saved them. I clamped the extensions on in the proper position and sighted down them a couple of times to make sure they were straight. I tack-welded the extensions, removed the clamps, and completed the welds down both sides. My welds are not that elegant yet, so I used an angle grinder to take off the high points and smooth them out.

I should say that welding was not strictly necessary to the project. A couple of U-bolts on each side might have secured the extensions, or a couple of holes drilled through extensions and bar for standard bolts, nuts and lock washers. I did load test my welds by pulling really hard on the extensions to make sure they wouldn't easily break off.

I cleaned the whole rack and spray painted the welds and other chipped spots with matte black paint. I put the wheel holders back on the extensions. I placed the tandem on the rack, adjusted the wheel holders so that the bike was centered and well supported, and marked the extensions a few inches beyond the holders for cutting off excess tubing. I cut the tubing with an air cutoff tool and put the end caps on the ends of the extensions. I had a piece of pipe insulation lying around so I cut it to fit the vertical support bar on the rack and zip tied it in place. It will protect the paint on the bike frame.

Step 2: Fat Tire Bike Carrier

Fat tire bikes are great fun, but those big tires make them unsuitable for many bike racks. I had purchased a pair of used car-top bike carriers much like the Yakima Frontloader, but I think mine is an older model. The fat bike will not fit in them directly, but I thought with a bit of modification, it might. The bike is held in place at three points, and each required alteration. The front wheel is held in place by two loops that basically pinch the tire front and back. The rear wheel is held in place by a strap tightened onto a saddle that cradles the tire.

The front loop holds the foremost aspect of the front tire in place and is adjustable for bikes of different sized wheels. Even on the highest setting, however, the fat tire will not fit. Modification consisted of simply removing the plastic height adjuster. Using an electric drill and a drill bit the same size as the rivet, I drilled out the rivets holding the height adjuster in place (see photos). Once the adjuster was removed, the front tire, 4.8 inches in my case, fit into the loop snugly. Incidentally, I saved the height adjuster and replaced the rivets with small bolts and wing nuts so that I can put it back on the rack and carry a standard mountain bike, which I have done.

The rear loop holds the rear aspect of the front tire in place after the loop is rotated forward and tightened with a knob. Again, the fat tire does not fit because of the plastic fitting and lock. I removed the plastic fitting, again by drilling out rivets, and replaced it with a rubber tarp strap. I cut the strap to length, inserted the ends into the metal tubing of the loop, and drilled a hole through them with the electric drill via the previous rivet holes. I ran some bolts through it (this is the hardest part of the entire process, to get the bolts through the rubber strap) and secured it with a nut and lock washer. The rubber strap holds the rear of the tire and provides some flex. I check it periodically for weathering because rubber does not last forever.

The rear tire is normally held in place by a proprietary plastic strap. For awhile I had daisychained two straps together to accommodate the large diameter of the fat tire, but lately I've just been using a short nylon strap with a buckle closure.

I've used this rack now many times without incident.

Step 3: Bonus Fat Tire Bike Carrier

I also created a way to carry the fat tire bike in my pick-up truck. Sometimes we participate in bike festivals, and I pull a travel trailer behind the truck so we have a place to spend the night. I had already made a 3-bike rack for the truck bed with two 2" x 6" boards and three skewer-type front fork holders:

My truck bed has slots in the sides for holding two-by lumber in place. I put one mount in the center of the rear board, and two on each side of the front board to hold 3 bikes.

The fat bike has through-axles, which won't fit on the skewer holders, so I ordered one for the through-axle fork:

Since the fat bike is longer than a typical bicycle, I simply screwed a length of 2x6 ahead of the pre-existing skewer mount and attached the through-axle mount (see photo). It has worked quite well, and the skewer mount is still usable.

Step 4: Bonus Tandem Carrier

I got a new, lighter tandem (43 lb) that I can lift onto the top of my car by myself with relative ease. In this step I'll show how I cobbled together two bike carriers to make a tandem carrier. I already had a Honda (made by Thule) rooftop bike rack (Honda Part # 08L07-E09-100) mounted on my car for carrying my conventional bicycles.

I added the wheel tray from an old Yakima Copperhead (discontinued) bike rack that I had lying around. I removed the crossbar mount from the front of it using a Torx driver. I placed the front of the Yakima tray in the rear of the Honda tray and used the rear wheel strap of the Honda rack to hold it down. I placed a short length of 2" PVC pipe under the strap to distribute the force over a larger surface area. See the photos for this part. The strap holds the tray securely, and I can push down on the rear of the tray fairly hard without producing much of a deflection. I adjusted the Yakima tray to fit the length of my tandem. I used the rear wheel strap of the Yakima tray to secure the rear wheel of the tandem, as one might expect.

I had planned to bolt the two trays together, but the strap seemed like an obvious solution, and it has the advantage of being quickly reversible. Probably, if I were taking a long trip, I would add some straps or zip ties for increased security. Actually, when I brought the tandem home, I didn't have this system set up and I just let the rear wheel sit on the roof of the car, which didn't scratch the paint or cause any other problem. I did use a ratchet strap to hold the bike frame to the rear crossbar though.

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