Ford Raptor 37 Suspension Deep Dive | Look ma, no leaf springs!

·13 min read

There probably isn’t a Suspension Deep Dive vehicle I’ve anticipated more than the 2021 Ford F-150 Raptor. But I tend to say that every time I get my hands on an all-new vehicle. It was true before I laid hands on the 2022 Ford Bronco I looked at recently, and I had the same thought when the 2021 Ram 1500 TRX paid a visit about a year ago.

But this feels different for a handful of reasons. For one, the new third-generation has a five-link coil-spring rear suspension, and that’s something not shared with any other F-150 or anything in the massive F-Series lineup. This was a ground-up design with the high-flying Raptor in mind. This makes it different from the five-link coil-spring rear suspension on the Ram 1500 TRX, which is a revision of existing Ram 2500 Power Wagon link geometry – albeit with better shocks and other significant tweaks.

Not only that, the Raptor’s new underpinnings really work. I was able to absolutely wring a couple of different Raptors by the neck (the standard 35-inch tire version and the new 37-inch version) during my First Drive at Dumont Dunes, a sprawling off-highway vehicle (OHV) recreation area in California’s Mojave Desert. Since then, I’ve also driven the 37-inch-shod truck you’re about to see on familiar, poorly-maintained roads near home in Orange County, Calif. This new Raptor is not just an ass-kicker when driven hard in the open desert, it’s also an utterly livable daily-driver.

The main reason for the third-gen Raptor’s newfound depth and breadth of suspension performance is in fact that fantastic five-link coil rear suspension. Ford has also fitted Fox internal bypass Live-Valve adaptive dampers and optimized them for the new suspension. Now that I’ve driven it, it’s time to pull the wheels off for a closer look I’ve just been dying to take.

Like the Raptor before it, this third-gen Raptor rides on a wide-track double wishbone front suspension, but there are numerous revisions that have increased maximum wheel travel from 13 inches to 14 inches.

Regular F-150s, like the 2021 XLT 4x4 I looked at last year, are built with much less track width and provide significantly less travel. That truck had welded steel upper and lower wishbones, but here we can clearly see the upper wishbone (yellow arrow) is forged steel and the lower wishbone (green) is made of aluminum.

This year’s Raptor uses a new generation of Fox internal bypass coil-over shocks (yellow) that are, among other things, allowed to grow longer than before. Another travel improvement stems from the reshaped and reoriented axis of the upper ball joint that now allows more angularity as the steering knuckle is turned through its full range of motion.

Below, the lower shock attachment (green) is a large double-shear through-bolt. This is similar to the last Raptor, but quite different from the regular F-150, which uses a tie-bar held to the top surface of the lower wishbone with two smaller bolts.

The Raptor’s aluminum lower wishbone is strengthened by an integrated crossmember (yellow) that spans between its two legs. Further outboard, the lower wishbone and the steering knuckle feature prominent nubs (green) that work together to act as a steering stop.

Higher up, the Raptor uses the new, regular F-150’s electrically actuated, vacuum-operated Electric Integrated Wheel End (EIWE) to lock and unlock the front hubs as you switch in and out of four-wheel drive. These differ from the older IWE design, in that the electric actuation happens here at the hub using a control wire (red) that’s just below the vacuum line.

Here we can see how the steering stops on the lower wishbone and steering knuckle interact as the steering approaches full lock. We’re not quite at full right lock in this picture, but we’re getting close to the point where they’ll touch.

As in the regular F-150, the Raptor’s lower wishbone attachment points (yellow) lack the eccentric cams we’re used to seeing. They say the manufacturing process is so dialed in that they don’t need to build in adjustment, but I’m not buying that. Besides, we can see a witness mark where the nearer one either slipped or someone used the available hole-slop to make a minor adjustment.

The Fox shocks develop a base level of damping within the main body of the shock, with internal bypass holes we can’t see along its length to give the damper position sensitivity. The damper is therefore soft in the middle but stiffens up as the piston moves toward the compression or extension extremes of travel. Layered on top of that is this computer-controlled live valve (yellow), which adds additional damping depending on conditions. This year’s version has a sample rate that’s 10 times faster, so the system is a lot more responsive to road conditions in real time.

Above right we can see the upper wishbone, but there’s a lot more going on than you might think. Now, rather than making you open another browser window and find the similar photo I took of the 2021 F-140 XLT 4x4 a few months back, here's two versions side-by-side (without the text associated with that pic, ignore its yellow arrow)

The crown of the upper shock (yellow) mount is *much* taller than a regular F-150’s, and the vertical stiffening webs (green) extend much lower down on the frame. This was done because the Raptor’s shocks are quite a bit longer, and this upper mount has to be considerably stronger.

Lost among all this is the height sensor (red) that tracks the suspension’s position constantly and feeds it into the Live-Valve adaptive damping computer.

Inside, the front bump stop (yellow) is plain to see. This one is particularly long to the point where it needs a stiffening ring, because Raptors shod with 37-inch tires get longer bump stops to restrict the front travel to 13 inches. The 35-inch version should have a shorter stop that enables the full 14 inches of travel. The restriction is needed because the big 37-inch tires would otherwise stuff themselves too far up into the fender wells, and the danger of rubbing is especially acute when the wheels are turned at the same time.

Unlike the regular F-150, the Raptor’s stabilizer bar link (yellow) still attaches to the lower wishbone. It’s a tidy installation, and the stabilizer bar pivot bushing (green) is close by. What’s not available here is the kind of stabilizer bar disconnect mechanism that Ford just introduced on the new Bronco. The Raptor could use the option, I think, because the front tires don’t compress all that much on the way to a Flex Index score of just 537. Of course that’s this 37-inch truck. A Raptor shod with the standard 35-inch rubber and therefore more travel might do better if the stabilizer bar isn’t the limiting factor. Who knows? Maybe the disconnect mechanism is being held in reserve for the Raptor R.

The various motion ratios are easier to see from the back side, although this angled view mucks things up a bit. The stabilizer bar linkage attaches about 45% out from the inner pivot, so we’ll call it 0.45-to-1. Meanwhile, the coil-over spring and damper attach something like 75% of the way out. But there is a bit of lean to the damper, and it will only increase as the suspension compresses. If we say it is laying at 25 degrees from vertical, then a cosine factor of 0.91 comes into play. That brings what at first seemed like 0.75-to-1 down to 0.68-to-1. Or thereabouts. As ever, these are eyeball estimates.

The Raptor uses twin-piston (yellow) sliding calipers. These are so named because the twin pistons push on one side, but the caliper housing they are mounted within can slide freely on pins (green). In this way, the applied force on one side pulls the caliper’s far side toward the rotor, such that the forces are in balance and both sides generate the same clamping force. Ford has put in handy inspection windows (red) so you can readily see the pad/rotor interface and check pad thickness at a glance.

Look ma! No leaf springs. There’s a big honking coil spring.

Five-link rear suspensions have two trailing links (yellow) per side, and these are positively massive. I measured the lower one and found it to be just over 3 feet long. The upper one is the home of the rear suspension position sensor (red) for the Live-Valve adaptive dampers. Higher up, we can see how the upper shock mount (green) is a very beefy protrusion jutting off the frame.

This setup is good for maximum wheel travel of 15 inches, an inch better than before.

The coil itself is about 2 feet long out of the truck, but it’s somewhat smaller now. A jack stand is supporting the axle, so we’re seeing it compressed a bit more than it would be if the truck was on the ground. Still, the upper coils are in bind, because this is a dual-rate progressive spring. Those coils open up at full droop, which helps make initial engagement a bit more gradual as you land a jump before they stiffen up as you approach mid travel.

The inverted rear shocks have piggyback-style (yellow) remote reservoirs at the top. There’s a dividing piston in the reservoir, with extra oil that flows freely in and out of the main shock body above that piston, and nitrogen gas below that pressurizes the entire shock to keep the oil from cavitating as it squeezes through the very tiny passages that make up the various damping valve elements. One of those is a computer controlled valve-stack inside the Live-Valve (green) that piggybacks off the piggyback.

The front shocks have a dividing piston and gas chamber, too, but they’re smaller and in-line with the shock below the side-mounted live valve. No extra oil reservoir capacity up there.

The lower shock mount bolts to a bracket (yellow) that hangs under the axle tube, but so does the lower spring seat. What this means is that alternate spring seats can simply be bolted on. In fact, I am fairly certain (but don’t quote be on this) that the 35-inch Raptor uses different spring seats. The Raptor R may indeed go its own way here, too. This also means that an aftermarket suspension maker could dream up their own spring seats, which opens up possibilities that are not readily available on the TRX, where the springs simply plonk down atop the axle.

Lots going on here. First, note that the Panhard bar’s axle-end mounting point (yellow) is mounted pretty far inboard as it tries to stay clear of the spring, lower trailing arm brackets and the bump stop (green), which registers on top of the axle tube itself. The metal base of the bump stop housing protrudes downward more on this truck than it would in a 35-inch Raptor, because the rear end of 37-inch-shod Raptors must also trim an inch off their travel to prevent the fender wells from being overstuffed.

The spring and shock mount is welded directly to the axle tube, so their motion ratios are 1-to-1 when the suspension is moving up and down in unison or in-phase. But that changes in roll aka opposite phase, where the suspension can be said to pivot around the center of the differential housing. In that case the spring/shock roll motion ratio is about 0.75-to one based on the location of the mounting bracket relative to the tire’s contact patch, as we saw in the last shot. But the massive shock is canted forward quite a bit, so let’s take another 10% off the nominal 0.75-to-1 roll and 1.0-to-1 bounce damper motion ratios, which makes them 0.68 and 0.90, respectively.

The axle bump stop isn’t the only one on this truck, though. There’s another on the shock absorber, and it is just visible inside the stone guard.

The inset axle-end mounting bracket we saw before leads to a Panhard rod (red) that’s shorter than I like to see. With as much as 15 inches of vertical travel, we might see some visible left-right axle translation as this shortish bar swings through its arc.

Also of note is the axle breather tube (yellow) that runs from here up to a point near the left-rear shock’s upper mount. The end features a 90-degree fitting that actually terminates a little higher than the bottom surface of the bed. Nearby there’s a control wire (green) for the electronically lockable rear differential.

It is indeed a tight fit with a 37-inch spare tire back here, so much so that the Panhard bar is squeezed flat in the middle (yellow) for a little extra breathing room.

The rear brakes are made up of ventilated rotors and single-piston sliding calipers with electrically-driven parking brake actuators (yellow) mounted to the back.

The 37-inch wheels are beadlock-capable rims, but what you’re seeing is a non-functional trim ring (yellow) that does not actually overlap the rim’s lip to provide any bead locking. The functional beadlock rings that do that are an accessory, and you’ve got to unfasten all 24 Torx bolts you see here, times four (or five) wheels, to make the switch. The bolt holes do not penetrate the rim’s air cavity, so there’s no chance of any leaks.

These massive 37x12.5R17 LT BF Goodrich All Terrain T/A KO2 tires and their 17 x 8.5-inch rims with faux beadlock rings (and real beadlock bolts) weigh a cool 101.5 pounds. Woof.

More after the video ...

I don’t know about you, but I’m not disappointed by what Ford has done here, especially because this new rear suspension is clearly a Raptor-optimized design that wasn’t borrowed from another F-Series. And it works wonderfully, except for one place: my RTI ramp. Yes, the 37-inch-shod Raptor has had 1 inch trimmed from its maximum travel potential for clearance reasons. But that still puts it at 13 inches front and 14 inches rear, like the Ram 1500 TRX. So why did it score just 537 compared to the Ram’s 602 points? I’m not yet sure.

But let’s zoom out a minute. The Ram 1500 TRX and Ford F-150 Raptor are not bound for boulder-hopping escapades on the Rubicon Trail. They’re arguably far too wide for anything like that, and their main reason for being is high-speed desert running. Would I like to see more articulation here? Sure. Is it a deal-breaker? Absolutely not, because the new Raptor can absolutely haul the mail in the wide-open desert environment it was designed for. But, yeah. I’ll still take a look at the 35-inch shod Raptor with 14 inches of front and 15 inches of rear travel. And I would not complain if they suddenly made a Raptor version of the Bronco’s stabilizer bar disconnect mechanism.

Contributing writer Dan Edmunds is a veteran automotive engineer and journalist. He worked as a vehicle development engineer for Toyota and Hyundai with an emphasis on chassis tuning, and was the director of vehicle testing at (no relation) for 14 years.

You can find all of his Suspension Deep Dives here on Autoblog.

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