Aluminum was a little scary and the thin middle flaps in-between the main beams, that don't do much, have bent after multiple uses. We use these ramps two to four times a day for a John Deere commercial mower, so the smaller airplane style tires in the front (about the width of a dirt bike tire) are what is bending the center connector flaps. I really don't see a problem with this in our case and the ramps are super strong, sturdy and safe.
tim 
