1st 5th wheel

travelnutz wrote:
kaydeejay,

We see it differently but my view/posts are from actual conducted test data, engineering manuals, and written accepted Physics etc Laws.

The 12K on the 4 trailer's tires to road provides more friction on the roads surface per square inch of contact than will the 10.7K on the truck's tires would. Then add in the pulsing effect created by anti-lock brake systems on the modern truck when any wheel slides or rotates less RPM's as the others on the roads surface. The trailer's brakes do NOT pulse at all as they are electric solenoid constantly activated and apply continous braking force on all 4 wheels/tires and will apply more measured and calculated friction to the road's surface than the truck's tires will with it's higher load weight. Refer to the engineering manuals and it's very clear and what I had experienced in seeing test/certification videos. Most were done by the insurance institute but some were done on manufacturer's test facilities. I can't go into in depth detail as to which. Nor could you as a past employee.

I can simply turn the adjustment thumb wheel on my trailer brake control on the bottom of my IP to make the trailer brakes do all the stopping when my truck's brake pedal is just slightly depressed. OR Turn it the other way so the truck's brakes will do nearly all the stopping. It's a MUST to have the trailer be pulling backward on the tow vehicle in braking simply because having the trailer inertia pushing the truck in trying to pass the tow vehicle is extremely dangerous and deadly as it over comes the truck's braking ability.

Things in motion tend to say in motion. I think I read that somewhere from a guy named Newton! Claims it's the first LAW of motion. The external force counteracting the motion in the RV world is the friction between the road's surface and the vehicle's tires. More weight per square inch of tire foot print creates more friction on the same road surface. Hey, the OP's trailer's tires have more weight on them per square inch of contact on the road's surface than do the truck's tires right? Extremely hard to argue with that simple fact.

Nutz,
I have a friend who is a retired chassis engineer. He says we are both right!
You are correct under moderate braking in saying it is possible to dial in the trailer brakes such that they provide most of the stopping effort. I did not disagree with that statement.
Note the word "moderate".
However he pointed out that, in extreme braking situations, given a perfect road surface and a friction coefficient of 1.0, the 12,000# on the trailer can generate no more than 12,000# of braking effort. That is 80% efficient on a 15K fiver.
With the truck weighing (say) 7700# + 3000 of pin, at 10,700# those truck brakes can generate 10,700# of braking effort, enough to stop the truck at 1g PLUS absorb the shortfall from the trailer. That completes the 100% braking of the trailer and provides a potential 1g stop for the entire rig.
Of course, that 10,700# of braking is only good until the brakes fade out.
ABS is designed to maintain the wheel at the point of lockup without skidding. That creates maximum braking unless you are on a loose surface such as gravel.
It's much more likely the truck is at maximum braking rather than the trailer due to the delicate balancing act required to get close to, but not quite, trailer wheel lock-up. Once wheels start to slide, maximum braking effort is lost.
Under extreme braking situations I suggest there will ALWAYS be a push on the pin, whether it be the 20% example used above or more.