Introduction: Better. Faster. Stronger. Build Your Own Automotive ROOF RACK!

About: The IDEAWORKS Innovation Suite is part of the Library and Academic Technology department at Washington College in Chestertown, MD.

If you've been in the market for an automotive roof rack, you've probably noticed there are already a lot of options. Why take the time to build one yourself?

  • Better! - Since you know how you plan to use the roof rack, you can make it infinitely adjustable to your needs. Using 80/20 extruded aluminum make future changes a snap too!
  • Faster! - OK, maybe this rack isn't going to make your car any faster, but it is super quick to adapt to most any cargo needs! Using an allen key, you can slide and adjust tie-down points or rails in seconds. Add more cross rails, more tie-down points, all in no time.
  • Stronger! - The extruded 80/20 aluminum bars are super strong! Certainly the weak point in my roof rack is the car itself, not the rack.

Step 1: Designing Roof Rail Connection Plates

Not all cars have the same roof layout, so this approach certainly won't work for everyone. This example is for any cars with factory attachment points already available. If you have another roof type, you will have to come up with your own connection method.

On my Chevy Bolt, all the literature I can find about roof racks mentions a 160lb max capacity. Since this comes from multiple 3rd-party rack venders, I'm assuming this is based on the roof limitations. This rack would otherwise hold a lot more, so use your best judgement and research your vehicle. To get started, I discovered the thread size for my car's factory roof rails, which is for a 6mm bolt on the 2017 Chevy Bolt. The bolt holes aren't all in a strait line, but rather follow the contour of the roof. Each pair of holes was measured, and they all turned out to be the same distance apart, 120mm between holes. You can see the process I went through to find a good fit for my Bolt. In the 1st version, I made several sets of holes spaced the right distance apart, and used that to get a sense of the roof angle for the front and rear mounts. The 2nd version then has level mounting points. 3rd version was adjusted for an ideal height to clear the radio antenna. 4th and 5th revisions were for functional testing. I put them in place with my aluminum 80/20 rails to confirm it was a good fit and angle. Also, I knew I wanted to make these out of aluminum, so in versions 4&5 I modified the bracket with the angled fronts so I could condense the set of 4 pieces onto a single 6" x12" plate of 1/4" thick 6061 aluminum. Here's the final design I used for my Chevy Bolt as an Adobe Illustrator file.

Step 2: Testing the Connection Plates & Checking for Level

Before making these out of aluminum, I used 1/4" Baltic Birch. With access to a laser cutter, this made precision testing easy, and much cheaper and quicker than making it from aluminum to only realize I needed to refine the fit. You could use much of the early fit testing with cardboard, and then move to wood with whatever hand tools you have if a laser isn't available.

The side-view shot shows the 80/20 10 series 1x2 extruded rail attached, before I cut it to length. This helped me eyeball if the angle/tilt front to back was good. If the roof rack tilted upward, it would produce lift which could be dangerous at highway speeds if I was carrying something like plywood. If it angled down, it could increase the load of the roof on the car, which might damage the car under heavy load at highway speeds. In the end, to feel more comfortable than "eyeballing" the angle, I set a laser pointer on the extruded rail, and used a piece of metal shelf support to see where the laser intersected it from a close distance, then move about 20 feet back and measured again. If there was a significant angle up or down, it would be amplified in the measurement over this distance. I didn't use a bubble level since parking lots typically have some slope for drainage.

Step 3: Fabricating the Plates Out of Aluminum

This was the hardest step for me. I have access to a low-end CNC router, but it was going to be about 80 hours of cutting if I tried that. I hadn't cut anything from metal this size on the machine, and leaving it unattended made me nervous.

Instead, I used the laser cutter again to help me get precise measurements onto the 6061 aluminum plate so I could fabricate it by hand. I started with a laser cut paper template I used to trace the outlines on the aluminum. I was able to cut the aluminum to rough size with a bandsaw, and used a large belt sander to fine tune the shape. I found the aluminum got hot quickly since it conducts heat so well, so I periodically ran it under cold water and dried it before continuing. Once my outline shapes were very close, I sanded it by hand with wet/dry paper at 220, 320, 400, and 600 grit. This gave the surfaces a nice smooth and clean look. Next I cleaned it with denatured alcohol and sprayed Cermark on them. My 100w CO2 laser can't otherwise do anything to metals, other than etch through anodizing. Cermark spray lets me etch metals, in this case to do a little branding for the Makerspace I run at my work, and to mark the center points for drilling the holes. To line this up, I put a scrap of plywood in the laser and made a laser mark of the outlines. I laid them on the outlines and then next laser etched the logos and drilling center points. This isn't 100% accurate, since it is possible for me to have a handmade bracket not precisely line up with the laser marked guide, but it's close enough. The important thing is that all the laser marked drill points are precise with one another.

Step 4: Final Mounting of the Plates and Rails

For those who aren't familiar with 80/20 extrusions, I'll give a very brief overview. 80/20 makes extrusions that easily bolt together using a T-slot design. They also sell lots of connectors and accessories, kind of like an industrial erector set. The profile I chose was a 1"x2" from the "10 series" line. The holes I measured and laid out on the aluminum plates line up perfectly with the two parallel tracks of the extrusions, giving three points of attachment on the rail for each mount. To bolt them together, you just slide a flat T-nut in the end of the track, and attach with a 1/4 20 bolt. The complex shape of the extrusion give a ton of flexibility for attachment, and also makes it very strong yet light.

I cut the rails to a length that I felt was ideal for my car, and bolted it all together using threadlocker (Locktite) to assure these wouldn't loosen with road vibration over time. I don't plan to remove these rails, so I used the stronger bonding red Locktite.

Just a note, I used some adhesive backed weather seal foam, stuck to the 80/20 rail, where it comes in contact with the factory rail (car roof). I made this fit very tight so I had to compress the foam to get all the bolts to line up. This helps transfer the load of the rack to the car, and doesn't put all the weight on the bolts, since they are taking a sheer load. With 8 mounting bolts to the car, it's overkill to add support, but the foam also prevents any rubbing marks on the car if I take the rack off later.

Step 5: 3D Printed Supports and Aerodynamic Caps

I modeled the end cap in Fusion360, based off the diagram 80/20 provides. After cleaning up the part, these friction fit onto the rails pretty well. I didn't use any adhesive so I can easily pop them off if I want to slide in another T-nut for some reason. If you wanted to make them stick better without a permanent glue, try using silicone.

The support block slides in one of the T-tracks and wedges between the rail and the car-top. This is still a prototype piece I'm planning to refine later, but it does a good job as is.

The support was printed at 100% infill for maximum strength. I used PLAyPHAb filament which seems to be holding up to the UVs good so far.

Step 6: Add Your Cross Bars

This is again where you will make decisions based on your use intentions. My sub-compact Chevy Bolt was not the ideal vehicle for getting plywood from my local lumber yard. Up until this point I had the typical 5'x5' sheets of Baltic Birch wood ripped to a size I could fit in the back of my car. Even though this worked, it took up my whole back seat/cargo area, and I had to slide my seat all the way forward. Also, I don't want to keep using my car like a pickup inside. The wood gets sawdust in the car, and will scuff the plastic trim if I'm not careful.

I wanted a roof rack that was 64" wide, so I could fit a 5 foot (60") wide sheet of plywood up there, and have 2 inches on each side for brackets that hold the wood safely in place. I bought four 10 Series 4 Hole - Tall Gusseted Inside Corner Brackets as my tie-down points on the cross bars. They are high enough to keep a few sheets of plywood centered, and I can easily run a rope through the triangular shape. All I need to do to adjust them is loosen the bolts with an allen key, slide, and re-tighten. Super easy. Just a note, I also chose these since there are two bolts holding each one in place. One bolt is strong enough, but two provides a little redundancy, always a good idea.

To attach the cross bars to the roof rails, I used four 10 Series 4 Hole - Wide Inside Corner Brackets. I wanted the redundancy of two bolts into each part of the rack here, and with easy adjustability. Typically I'd use these with the cross bar centered, but there's no reason I couldn't slide it one way so there's a bigger overhang. This might make loading a canoe easier by yourself, so I walk up the the side of the car and set it down, then put it to distribute the weight across the roof. I don't plan to do this, but on a larger stronger vehicle roof, you could build a platform with a ladder attachment point here for camping up top. No need to find smooth ground for a tent.

To finish up the install I added flat covers to the ends of the cross bars, and a rubber tread strip along each cross bar. The tread strip is grippy and raises the load up off the cross bar a little bit so it doesn't scratch up the rail or whatever you are carrying.

I'd remove the cross bars if I'm not planning to use them. They do add a little wind noise, and wind resistance. I'm going to have a set of shorter cross bars that easily fit in the cargo area behind my passenger seat so I always have an option for carrying random stuff without planning ahead. But if I want to carry large sheets of plywood, I'll want to use these extra wide cross bars.

Step 7: Was This Helpful?

I hope this tutorial was helpful and useful, or at least somewhat inspiring to try something similar with 80/20 parts. This was my 3rd project using 80/20 supplies, and I'm really starting to like working with it!

If you want to show support and help our Makerspace out, please considering voting on this tutorial in the Metalworking Contest, and we'll be forever grateful! :)

Step 8: Full Parts List With Prices and Links

If you have a Chevy Bolt, you are in luck. Otherwise, consider you might want to make some adjustments to the length and width after you measure your vehicle. Also you can think about adding a 3rd or even 4th cross bar if that makes sense for your applications.

The 80:20.pdf file you can download in this step is a cart of all the exact parts I used from 80/20, totaling $182.45

Additionally, I used a 6x12 piece of 1/4" 6061 aluminum like this, priced at $14.25

Finally, I used some 3D printing filament, a couple dollars worth.

Total price installed: $200

What doesn't this total include?

Shipping from 80/20 for me was about $33.00, but I did include some other items not used in this project. If you had a local vender that sold 80/20, you could pick it up and save that shipping. I recommend doing that if possible. I found in the past that 80/20 extrusions bought on Amazon often come poorly wrapped and get scuffed. For industrial framing or something in a shop, no biggie. If this is going on the roof of you new car, you'll want it blemish free. 80/20 does an impeccable job wrapping and shipping the parts, really very excellent. But in my case it was about 2 weeks between when I order online and when they shipped it UPS ground. Almost 3 weeks before I received the order.

Step 9: In Action!

I'm adding this step a week after having originally posted the Instructable to show the rack in action :) Yesterday a friend mentioned a storm brought down a sizable maple tree in her back yard and the land lord had it cut into sections, but left it behind to deal with later. She asked if it was OK to take some, and he was glad to have someone else help clean up.

I've got access to a 14" bandsaw and I've been trying to learn to resaw sections of tree like this to make live edge slabs like those pictured here. These aren't my slabs... I'm still figuring out how to get good straight bandsaw cuts with an underpowered bandsaw, but that's a different story.

I just wanted to share the roof rack carrying 100lbs+ of log, about 10-11" diameter, and having no trouble with the weight. I didn't go far with it, or I would have lashed a bit more. On the other side of the rack you can see some long sections of aluminum tube I'm working with in another project. The rack has been great so far, and I don't really have any thoughts for changes if I were to do it again.

Metalworking Contest

Runner Up in the
Metalworking Contest