Truck Stops Truck / Trailer Stops Trailer?

wowens79 wrote:
I didn't want to get off topic on the debate about the guy pulling the 5ver with a 1500, but the truck brakes being adequate was brought up, and I wanted to get some thought on this.

Lets say there is 1500lb of pin weight as a nice round number. That 1500lbs is on the rear axle of the truck, so the trailer tires don't have that weight on them, so they would have less traction, but that 1500lb would be on the truck, so that would give the truck additional weight/traction to stop. In this case in an emergency stop situation isn't it possible that the light duty truck may not have enough breaking power to get the maximum breaking affect??

Under normal conditions I'd think the trailer/truck brakes would work together fine, but in an emergency would you get maximum braking??

Also the bigger brakes on an HD truck would dissipate heat better, and would not fade from heat.

First off, the pin weight is never on the trailer tires and the trailer brakes do not stop the pin weight. Think axle brakes, not trailer brakes. A 6000 lb. axle doesn't know if it is on a fiver or a TT and it isn't carrying the pin or hitch weight, the truck is. It isn't stopping that weight either, be it a 600 lb hitch weight or a 2400 lb pin weight.

Second, you don't want the truck brakes stopping what should be stopped by the axle brakes. That means the trailer is pushing the truck and could result in loss of driver control. How are police trained to stop a vehicle? By bumping it in a rear corner. You don't want a fiver having the same effect when truck and trailer are on slightly different momentum paths. Also, the hitch point is a good 24 inches above the truck axle center-line, so if the trailer is pushing the truck it is loading more weight on the truck's front axle and less on the rear axle, front ABS will kick in and the truck rear brakes will be underutilized. You really want the entire mass of truck and trailer to slow down at the same rate (or better yet as described below).

An emergency stop isn't just about stopping distance but stopping control as well. If you understand the ideal way to stop a fish-tail from getting worse, it is to manually apply the trailer brakes while accelerating with the truck. You are trying to pull the connection apart to keep both vehicles in line. When stopping, ideally you want the same effect, pulling the vehicles apart. And the only way to do that is really for the trailer axles to stop their weight faster than the truck brakes can stop their weight.

Where do you find the data that says a bigger, thicker rotor will dissipate heat faster than a smaller, thinner one? Performance rotors are slotted and cross drilled, or ventilated. More mass means a longer cool down, not shorter.

Anyone that is really concerned about safe stopping should focus on the trailer brakes first and truck brakes second. Too many of us think the opposite.