MX vs. ATV Reflex

I must really suck, I tried both methods above for 30 minutes and couldn't get it. Saw another solution on YT full credit to: Nillzilla & Rethgaa

Achievement actually pops at 1:38. They give a brief explanation during the beginning.

Try this if you're having issues with the other methods. Basically the middle ramp on the loading screen map is 75m. It's a lot easier doing it over that ramp rather than a large hill.

Set the user camera so it's looking at you side-on (like Trials HD). Find a slope leading to a wide open space. Press Y to set your marker once you're ready (B to return to it when you crash) and go for it. Once you're going fast, push the right stick forward and hold it, and hit the brakes.

Squeeze and release the brake to keep yourself balanced on your front wheel.

To start off, you can set the user camera to look at you side-on. (Credits to Suicide Perkies). Find a wide open space. Arizona's Free Ride is perfect. If you turn around 180 degrees, you'll find a sloped trail leading up a hill. I actually found that this was easier to do on a slope. Set your checkpoint marker at the top and begin to attempt the stoppie. If you go fast enough, 75 ft won't take a long time to cover. The gravitational acceleration of the slope will definitely help you get up to speed really fast. Another benefit of the slope of the hill is that it makes it easier to start a stoppie due to the angle involved. This is how I ended up getting the achievement. Just try it a couple times, and you'll have it.