Truck Stops Truck / Trailer Stops Trailer?

Yes, the HD truck would have a better chance in the scenario you describe.

if the brakes lock up or go into anti lock mode, you are getting the full braking. The additional weight on the axle is actually additional weight on the force of the tire as it touches the ground. I was taught this in Accident Reconstruction school...more weight equals more downward force. So as long as it does not prevent the wheel from locking up or going into ABS mode, it will all equal out

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.

Well 1/2 ton trucks can have a huge difference in the GAWR so which 1/2 ton truck are you thinking about.

A F150 with a 4800 rawr and 3750 FAWR = 8550 lbs of braking performance. The truck may weigh in the 5500-5700 lb range.
The trailer may have two 4400 lb axles = 8800 lbs of braking performance or 17350 lb combined braking performance.

IMO folks overthink the braking issue on these new gen trucks. We simply don't have braking issues like we did with our trucks in the '50s/60s/70's era.

JIMNLIN wrote:
IMO folks overthink the braking issue on these new gen trucks. We simply don't have braking issues like we did with our trucks in the '50s/60s/70's era.

x2. Truck brakes are much better than years past, and it's a good thing. I think the truck does much of the combination stopping. Trailer brakes are typically drums (with some exceptions) and typically don't employ an ABS. With the brake controller dialed in perfectly it's possible to get great performance out of your trailer brakes, but I doubt a truck and trailer combo would ever be able to stop as quickly as the truck alone. It would be interesting to see the results of testing.

Truck is designed to stop the truck at it's GVWR.

Sometimes trailer brakes stop the truck. A few years back my trucks brake line failed due to rust. I drove the rest of the way home (60 miles) just using my trailers brakes. Really surprised on how well they worked.

Cummins12V98 wrote:
Truck is designed to stop the truck at it's GVWR.

Very true. My FORD manual states the same.

Guess you shouldn't exceed your GVWR. ;)

I can quote you on this?

spud1957 wrote:

Cummins12V98 wrote:
Truck is designed to stop the truck at it's GVWR.

Very true. My FORD manual states the same.

Guess you shouldn't exceed your GVWR. ;)

I can quote you on this?

Yes you can since I am at or under my axle ratings and have proper tonnage for the load and I am also under my GCVWR that is a SAE rated amount. ;)

I do believe there are exceptions to this with a modern Dually.

Truck Stops Truck / Trailer Stops Trailer?

I had my trailer brakes go out on one of my trips and was darn glad that I had upgraded from SRW F350 to DRW F350. As it turned out the failure was due to drum brake magnet wear.

Anyway, the ability of the 13000 lb 5th wheel with 0 brakes to push the rear of a 9000 lb DRW truck sideways (jack knife) is incredible during heavy breaking. Not sure I would want to test a similar situation with SRW. Moral of the story is that Trailer does not always stop trailer.