General Discussion
In reply to the discussion: A time lapse video of me loading my car hauler (Edited with a new, BETTER! video) [View all]A HERETIC I AM
(24,891 posts)Several reasons.
1) With very few exceptions, the angle from the bottom of the tire to the point where the first material/bumper/muffler whatever will make contact is GREATER at the rear of the car than in the front. In other words, if you were to pick up the car with a tow truck, you can lift it higher if you pick it up from the front than if you pick it up from the rear. This is true for the overwhelming majority of production cars made worldwide.
Having said that, the center position in this load configuration is "Split-Decked" where the steer tires and rear tires are on two separate platforms. Here is that very car and you can see the fronts are on a different deck than the rears;


So I need to back it in because of the angle it will sit when rolling down the road. If I drove it on and had it at that angle, the underside of the front bumper would be subject to damage.
2) Weight distribution. While not critical with this load, as they are all fairly light cars, backing that center unit in places the weight of the cars engine over the trailer tires, thus more evenly distributing the weight.
3) Height. With this particular model, since it is a boxy little crossover, if I had driven it on, the back end would be sticking up much higher than the front is now. I have units on the deck above that have to come down to 13' 6". Backing that car, and indeed any car on makes it much easier to get the trailer down to statutory height. The hood is almost always lower than the rear or trunk.
One other thing that goes to point one; With most cars the distance from the vertical centerline of the front tire to the tip of the front bumper is ALMOST ALWAYS shorter than the similar dimension at the rear. For that reason it is usually the case that the first unit on the top of the trailer - the 3rd one I loaded - is backed on. The reason is so that the extra room the trunk and that overhang takes up is out in the wind and not crowding up the limited space I have on the upper deck. The reason I didn't back it on with this load is that the Kia Soul is one of the few that the front is longer than the rear. Of all the models my firm carries, only 3 or 4 have similar dimensions. The Nissan Cube is one and the Hyundai Veloster is another.
I hope that makes sense.