Dustydog said:
Find a safe place, test track. Get upto 50 mph and do an emergency stop.
Hitch up and repeat with the caravan on the back. The results will speak for themselves.
BHP and torque are important but the final drive ratio and gearing also play a very important part.
I seem to recall that a set of emergency stops with and without a caravan were carried out, either by one of the clubs or a magazine, and yes the results were interesting, but did not give the result you might have been expecting.
Emergency stops did take some extra distance but not as much extra as you might instinctively think.
The reason the stopping distance didn't increase dramatically is due to the way the trailer breaking system works.
When the car starts to decelerate the inertia of the caravan tries make it catch the car up, but by doing so, it compresses the over-run hitch, which starts to activate the caravans brakes.
As the stopping effect of the caravan brakes is dependant on how hard the overrun is pushed, the brakes apply progressively and according to the closing speed of the caravan to the car.
After a small fraction of a second the caravans brakes will start ****** the caravans speed until it again closely matches that of the car, at which point the caravan brakes will ease off.
The consequence of this is the caravan will only apply a relatively small amount of thrust to the ball coupling even under severe braking.
The movement in the overrun coupling means the actual mass the cars brakes are having are still principally retarding the car, and the caravans brakes are retarding the mass of the caravan.
The car only feels and has to deal with the force necessary to compress the overrun coupling, not the whole weight of the caravan.
If any brakes lock up the situation changes.