2020 Ram 1500 4x4 Suspension Deep Dive

What is taking everyone so long? That’s what I continually ask myself each time yet another all-new full-size pickup comes out with leaf spring rear suspension. Meanwhile, this 2020 Ram 1500 pickup represents a dozen years since coil spring rear suspension debuted when its prior generation was still being called a Dodge Ram 1500. Ford, Chevrolet, Toyota and Nissan introduced full redesigns of their pickups well after Ram proved that coil springs were the way to go, and yet leaf springs persist with the competition.

I’m not just popping off, here. In the 1990s I used to specialize in pickup truck suspension tuning for the Toyota Technical Center. Leaf springs are crude and loaded with compromises, but that’s all that truck design engineers ever gave us to work with. I was instantly all-in on Ram’s move to rear coils after the first few miles of driving a 2009 Ram 1500 pickup. Empty-bed ride comfort and handling were on another level, but it could still tow and haul. In fact, towing stability proved to be frankly incredible on the normally-treacherous downhill leg of my winding tow test grade. I fully expected everyone would copy it immediately.

But they didn’t. Others may have doubted the payload aspects. Ram never did. It soon doubled down and put coils under the back of its 2014 2500-series trucks. I’ve developed other theories that seek to explain why no one followed their lead, but they’re not worth dredging up because I think the dominoes will soon begin to fall. Spy photos suggest that the next Toyota Tundra will switch to coils, and there are rumors that the Ford Raptor is going that way. That’s not much of a stretch because the Ranger Raptor (only available outside the U.S.) already has coil spring rear suspension.

What’s the big deal? Let’s take a look at the underside of a 2020 Ram 1500 Laramie 4x4, the second iteration of the Ram 1500 to employ coil spring rear suspension.

As it has for some time, the front end of the Ram 1500 rides on double wishbone suspension. The truck employs a high-mount upper wishbone (yellow arrow) that positions the upper ball joint up behind the tire sidewall instead of inside the wheel’s barrel. This layout offers improved steering geometry and reduced stress in the upper ball joint, the upper control arm and its mounting points.

Coil-over spring/shock assemblies (green) come standard on all 2019+ (fifth-generation) Ram 1500 pickups whether they have four-wheel drive or not. But the presence of coil spring rear suspension has bearing even up here because it allows Ram to offer four-corner air suspension as an option.

If that option were present we’d see a cylindrical air spring enveloping the front shock instead of coil spring. The small ball on the upper control arm (yellow) would be connected to a linkage feeding into a suspension position sensor to help the system manage the vehicle’s ride height.

The lower wishbone (yellow) and steering knuckle (red) were made of aluminum in the prior generation, but further weight reduction and design optimization steps have been taken. That’s most obvious when looking at the lower wishbone, which no longer has an extra flange on this side for the front stabilizer bar linkage. Camber and caster adjustments are made with a pair of eccentrics (green) at the wishbone’s mounting points.

The upper control arm is quite broad, and the coil-over shock is not centered between its arms. The reason for this seems to be that the shock’s lower mount is positioned next to the front drive axle, and the shock body is at full width at the point. If you’re not with me, don’t worry. We’ll see more of this later. Besides, the breadth of this wishbone is not its most interesting aspect.

That upper wishbone is a highly-engineered piece made up of two parts that are bonded together. The upper surface is a thin but deeply-drawn steel stamping (yellow) that is welded to otherwise-normal cylindrical steel bosses that house its pivot bushings. This creates a deep u-shaped steel shell, within which they have bonded a molded composite structure (green). The end result is an upper arm that is considerably lighter than it would be otherwise.

Weight reduction isn’t the only benefit of this construction. This arrangement undoubtedly transmits fewer road vibrations in through the chassis and on to the cabin.

This photo may explain why the upper wishbone is so broad. The shock absorber maintains its full diameter (yellow) all the way to its mounting point. The piston within can use most of the visible length. This obviously makes the lower end of the damper fatter, but that in turn means it must reside farther forward (left in this view) to stay clear of the drive axle.

If this was a Toyota we’d see a slender rod in this area, with the shock’s working diameter ending above this point. That allows their shocks to hug closer to the axle, but such shocks must extend higher at the top to maintain sufficient suspension travel. This may explain why the Ram’s high-mount upper arm pivot (and the upper shock mount that’s usually part of that structure) isn’t positioned nearly as high as we’d see on a Toyota.

The 2019+ Ram 1500’s stabilizer bar (yellow) has been moved from its former position ahead of the axle to this position behind the axle. It’s a very tidy installation. They say it results in a 20% increase in roll stiffness, but the old installation seemed to have room enough for fatter bars that could offer that kind of gain.

I think the real reason for the increased roll stiffness has to do with the capacity of the linkage mounting point (green) on the lower wishbone. The old design’s mounting point was a flange that protruded away from the main wishbone casting. They were probably near the limit of what it could take. Whether that’s strictly the case or not, this design transmits the stabilizer bar load into the very meaty central part of the wishbone. I like how it mirrors and counterbalances what’s going on with the shock, too. All of this results in a tidier and lighter lower wishbone design.

The distortion in photos like this always make estimating motion ratios a little dicey, but I’m going to plow ahead anyway. The point isn’t to reverse engineer this truck, just see what it's all about.

Looking first at the inner pivot at the frame and the outer ball joint at the steering knuckle, our spring shock assembly bolts to the arm about 75% of the way out. Every inch of suspension travel will result in 0.75 inch of spring and shock movement.  The stabilizer bar link looks like it lines right up with that, but you’ve got to follow the mounting bolt down from the flexible joint hidden inside that rubber bellows. That reveals a motion ratio of about 60%, or 0.6 inch of stabilizer bar linkage movement for every inch of wheel travel.

Many trucks have mechanical steering stops, and the Ram 1500 is no exception. The lower wishbone has a special protrusion that matches up to a zone built into the steering knuckle. This one comes into play at full left lock, while a similar setup on the passenger side does the job at full right lock. This doesn’t happen often, and there’s never pressure for extended periods, so it's fine. I prefer this to having the steering gear itself hit a hard internal limit.

Normally we only see the bumps in the casting that give away a caliper’s pistons, but here we can see where this sliding caliper’s two pistons press against the inner brake pad. But it's not just the inner pad that does the work. The caliper itself slides (hence the name sliding caliper) on two pins as force is applied so that half of the clamping force generated by the inner pistons passes through the structure to the pads that are arrayed on the opposite side of the rotor.

It’s like grasping something between your fingertips and palm. Your fingers appear to be doing all of the work, but the item you’ve grabbed is experiencing the same clamping force on both sides.