Photography by Evan Sears
Big truck fans know that acceleration is only part of the equation; safe towing depends on how well and how comfortably a truck and trailer controls its load. In our experience, this does more to define the strengths and weaknesses of a heavy-duty full-size pickup than just about any other characteristic.
We began the braking portion of this test at the same location we conducted our first acceleration runs, on a flat section of road outside Denver with one of our Load Trail flatbed trailers loaded with a 14,350-pound military half-track troop carrier.
Because of the variations we found in our runs and given the unevenness of the pavement, we decided to take the top two stopping distances that these trucks could manage and average them to get as close to a repeatable real-world number as possible.
Admittedly, the stopping distances at higher speeds for trucks this big are not good, especially when compared to their smaller half-ton siblings, but the numbers tell a story, especially when you compare them. We brake-tested the 2013 Ram 3500 HD and 2013 Ford F-450 from 40 mph with and without the trailer.
Without any cargo, and with two adult males inside (one driver and one data recorder), the Ford F-450 averaged 117 feet, whereas the Ram HD stopped in an impressive 104.5 feet — impressive because the Ram has smaller discs at all four wheels.
For the "fully trailered" braking tests, we disconnected the trailer connector to extreme test each truck's brakes to their limits, rather than making the test about how well the trailer's brakes help the big trucks stop. We did something similar in our 2011 Heavy-Duty Hurt Locker test with some interesting results. We don't recommend trying this at home.
We hooked up the 22,620-pound trailer to each truck, ran them to 40 mph and then hit the brakes, hard. What we found was that the F-450 stopped in an average distance of 165.5 feet, while the Ram HD — once again impressing our testers — averaged a distance of 148 feet. As you can imagine, both groaned loudly when trying to stop all that weight.
Exhaust Brake Showdown
One of the biggest benefits of choosing a big turbo-diesel in the heavy-duty segment is that the turbochargers can be used to help create engine back pressure to slow the engine down and keep truck (and trailer) speeds under control. This played a big role in one of our favorite tests, the Rumble in the Rockies, not to mention the Heavy-Duty Hurt Locker.
In those two tests, where we did a lot of towing near a truck's limits (just like this one), we saw how helpful and — in some cases — absolutely necessary a good exhaust brake can be. Likewise, advancements in automatic transmission grade braking have helped tremendously. These important pieces of technology, along with a fully functioning and well-prepared set of trailer brakes, are the keys to towing safely. The trick is how to test those capabilities without falling outside the boundaries of safety.
To test the smartness and capability of the exhaust brakes, in our Davis Dam runs we set the cruise control to 50 mph (the legal speed limit there) and engaged both the Tow/Haul mode and exhaust brake on the Ram 3500 HD. We especially liked that Cummins-equipped 3500 HDs have a Smart Brake function that offers two levels of exhaust brake aggressiveness: "Auto" is meant for all-around usage, while "on" provides maximum performance. We ran all of our exhaust brake testing runs in the "on" position.
During the first run, the Ram's Aisin transmission was quick to downshift all the way to 3rd gear, revving the engine on one particularly steep stretch to 3,500 rpm until the halfway point, then upshifting to 4th gear for the remainder of the run. Any time our speed exceeded 56 mph, we brought the speed back down to 45 mph by braking and then we let the truck go again. For that full 10-mile run we needed to touch the brakes on the Ram seven times. On the next run, where the transmission never did kick down to 3rd gear, but instead only got down to 4th gear, we needed to touch the brakes 12 times during our 10-mile Davis Dam descent.
The Ford F-450 was a little different, due in large part to the fact it doesn't have a dedicated separate exhaust brake activation button. Instead it uses the turbocharger as an exhaust brake only when the Tow/Haul button is engaged, where the auto grade braking and turbocharger work together in an attempt to control truck and trailer speeds. Unfortunately, it doesn't do as good a job of slowing the vehicle as the Ram's bigger, more aggressively tuned Cummins turbocharger. Down the Davis Dam section, we had to brake 20 times on the first run and 18 times on the second F-450 run.
We conducted the same test on the Eisenhower Pass as well, keeping all the procedures and parameters the same. Although the overall course is shorter (just 7.2 miles), it is much more intimidating given the fact it seems steeper and there are two well-marked truck runoffs filled with deep gravel for semis that lose their brakes. During this part of the testing in Colorado, we needed to touch the Ford brakes 18 times; the Ram HD needed braking support to help with slowing just 11 times.
Temperatures May Vary
We measured brake rotor temperatures right after our brake touch testing, in an effort to determine exactly how hard the brakes of each vehicle had to work. To do this, we used an infrared thermometer with laser targeting (about $50 at Harbor Freight Tools) and measured the heat of the rotors at the end of each of our downhill exhaust brake testing runs.
At the end of our Davis Dam runs down the 10-mile hill descent, the Ford F-450 front brake rotors were 375 degrees, while the front brakes of the Ram 3500 HD were 262 degrees. This is what you'd expect, given the fact that the exhaust brake and more aggressively tuned auto grade braking kept the Ram's overall weight under greater control.
At the end of our Eisenhower exhaust brake runs (which is a steeper and shorter hill descent), the Ford F-450 measured a whopping 1,105 degrees — with some glow and smoke included — and the Ram 3500 HD recorded 740 degrees, also with a good amount of cooking brake dust smell.