Originally posted by Ed & Debbie
I believe the single most common misconception about towing anything is the ability to pull it. Anyone who only looks at this factor is inviting trouble. You can tow some A/S's with a bicycle! Try to stop, dodge a road hazard, control a long down hill slope while over your vehicles rated capacity and then you will realize why all the H.P. &/or torque in the world doesn't mean anything.
Okay, in towing, you need to look at Torque, not just horsepower.
In its' simplest terms,
Torque is how much your truck will pull.
Horsepower is how fast it will pull it.
Torque is acceleration.
Horsepower is top end.
Since no one in their right mind would want to tow their trailer at 137 mph, the important thing is the grunt (torque).
You also need a vehicle with enough mass to keep the towed vehicle under control, that is why pickups and vans with long wheel bases are preferred.
The trailer will tend to make your vehicle pivot on its rear axle, as in a fulcrum. The farther away your front axle is from the rear axle, the more force the trailer would have to exert to cause the front axle to move, either laterally or horizontally.