Build Your Very Own Gravity Bike From Junk: An Insane Adrenaline Delivery System

What's a gravity bike, you say? Simply put, it's a modified cycle frame with no drivetrain or mode of propulsion except good ol' gravity pulling you down a hill. You could compare the dynamics to that of a luge, but as you can see, the rider is in a headfirst position and in a similar pose to those MotoGP riders.

It's rather difficult to pinpoint precisely when this sport took off, but it seems to have had time to create a little subculture where folks show up with their own home-built versions and start bombing streets with them. In the process, there have been deaths and serious injuries, and the trend is even being outlawed in countries like Columbia.

So why would I bring you instructions on how to build your own proverbial death trap? Because I'm an adrenaline junky, that's why! Yes, a gravity bike is something you will someday see me riding and creating some video content about the experience. Soon my pretties, soon.

But, if you simply can't wait to see me hauling down some pristine road and want to beat me to it, then these instructions on Instructables will be more than enough to get you in the game, in the process, creating your own unique machine with which to race your friends. According to S.I.N. Cycles, the builders behind the work today, speeds beyond 80 mph (129 kph) have been hit on these adrenaline delivery systems.

As for building your own, you will need some welding, cutting, grinding, and drilling experience. If you have the dexterity and know-how for this job, it's time to scrounge up all the scrap metal bits and pieces you may need. Some components were purchased to complete missing and/or essential structures, but the rest was fished from bins and piles of leftovers.

Then there are things like wheels and brakes, which I highly recommend grabbing as new and NOT acquired through dumpster diving. For the design you'll explore today, 20-inch wheels, L200 foam, rim brakes, and a wheel cover are needed. Oh, and some lead or cement to add weight to the trinket.

Things start with a prototype that's been measured and sized specifically for you, then it's on to the frame and axles. With some cutting, welding, drilling, and adding axles, things start to take shape. Tubing is added, including top, down, and head tubes, and it looks like some custom chopper job.

One aspect of a gravity bike that's not to be underestimated is the "kneeler," a space where you're to put your knees when finally in the riding position. And because your stance places most of your body's weight on the knees, any bumps or vibrations in the road will be felt, so you must use foam and not some steel plates or pegs. You can understand why.

One final aspect you need to be aware of when building such a machine is weight placement. One step of the build process requires that you either add lead to the front of the bike or cement, and it's all just to make you that much faster. That's what's hiding in that cannonball-like globe mounted to the frame.

From there, it's on to things like a paint job, adding a saddle, mounting the handlebars, which require some attention, and then the wheels. What do you have? A gravity bike! Time to find the most pristine downhill road and let this thing loose. Note of advice: wear full body gear because if you wipe out at 80 mph, it's 80 mph! It doesn't matter what you were riding; it all hurts the same. Get your dose of adrenaline safely.