Simply use some math:
mFPS = (16/time_frame);
speedGradient = 60 / mFPS;
tiledGradient = mFPS / 60;
And multiply your time_step with this.
It depends on how you want the code, so choose from my examples wisely, one will make it even more faster, one will slow it down so its always same speed

Use the 60 at all if the speed on framerate 60 is the one you wish to have!