I use the heavy duty "plastic" ramps, and have used them on all my vehicles, including the 8000lb Excursion. Most of my vehicles have been either Front Wheel Drive, or Four Wheel Drive, so they will just climb up on the ramps. Then I bought my P71, and the first time I needed to get under it, I chased the ramps across the garage. However, I discovered a trick so it would climb up the ramps just like a FWD or 4WD. I took 2 ratchet straps, take the long strap out of the ratchet, hook the hook on the flat side of the ramp (the side opposite the ramp) and put the strap under the ramp, and lay it out as long as it will go, so that it will go under the rear tires. Drive over them, and the straps under the rear tires will keep the ramps from sliding away when you drive up the ramps.