1st 5th wheel

travelnutz wrote:
kaydeejay,

Two very different scenarios!

Bricks in a truck's bed are only weight on the truck's rear axle and tires and their entire weight is stopped soley by the truck's brakes and by nothing else.

The 5th wheel pin equal weight on a truck's rear is attached to and part of the 5th wheel and is soley controlled by the brakes on the 5th wheel only.

I guess we are going to have to agree to disagree!
A wheel's braking capability is directly proportional to the weight it is carrying. If 3000# of the fiver weight is on the rear axle of the truck, the truck brakes will be doing the stopping in a hard braking situation.
Think of the perfect ultimate 1g brake stop with a friction coefficient of 1.0. To stop at this level requires the tires to apply a braking effort equal to the load on them. (They won't produce more than that)
A 15K fiver will have 12K on the wheels. THAT is the maximum braking effort that the tires can produce and no more. No way the trailer brakes can create a brake effort equal to the total weight of the fiver.
The rest of the weight is on the truck. The truck tires will produce that 3K extra braking effort because the truck tires are carrying the load. For that 1g stop the truck must produce a braking effort equal to its total weight. That includes the pin.
Your suggestion that the fiver stops the truck is only true under moderate braking conditions when the trailer brakes are more aggressive than the truck ones. It is under emergency brake conditions that the truck will do more work.