2021 Ram 1500 TRX Suspension Deep Dive | How it works

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I think we can all agree that we have been waiting for a gonzo full-size truck like the 2021 Ram 1500 TRX for a long time. After all, it has been over a decade since the Ford F-150 Raptor came out, and it was such an immediate hit that I expected its direct competitors to respond much sooner than this.

We all knew something was finally brewing in 2016, when the TRX concept was unveiled at the Texas State Fair. I was there, and was among the many who gave the assembled Ram higher-ups an enthusiastic thumbs-up. That’s what they were hoping to see before they greenlit the project. The pace of development being what it is, and with the redesigned, current-generation Ram 1500 a prerequisite that understandably had to come first, it’s no surprise that we’re only seeing it now as a 2021 model.

You may be biting your tongue that I overlooked the Tundra TRD Pro or the Chevrolet Silverado Trail Boss, but neither of those comes close to following the formula established by the Raptor: big engine, a much wider stance than the base truck, greatly enhanced suspension travel, huge tires and swollen fenders to cover it all. Only the Raptor and the TRX fit that mold. For now.

 

Before I got started, I first pointed the TRX up my RTI ramp and measured its Flex Index score. Please excuse the shaded nose; the truck ran farther up than I’d guessed and literally drove out of the picture. But something in my subconscious warned me to keep the garage door open, which was fortuitous because the nose of the Ram ended up inside.

The TRX hiked its front wheel 29 and 7/8 inches off the ground before the left rear tire reached the point of lift-off, and that equates to a climb of 87.4 inches up the deck of my ramp. Divide that by the TRX’s wheelbase of 145.1 inches, multiply by 1,000, and you arrive at a Flex Index score of 602 points. It could have been a few points higher, I think, if I could have straightened out the steering a bit better. But the high-grip cheese grater surface of my ramp was firmly dug in and having none of it.

This is an extremely good score for a full-size crew cab pickup. Let’s take a closer look at what made that possible.

 

The track width of the TRX’s double wishbone front-suspension is a full 6 inches broader than a regular Ram 1500, and you are looking at the parts that are responsible. The lower wishbone (yellow arrow), the upper control arm (green) and the steering knuckle (red) conspire to add 3 inches per side to the TRX’s stance.

We’re also clearly able to see the massive coil-over Bilstein Blackhawk e2 shock (white) and its beefy linear-rate coil spring. And by that I mean not progressive-rate.

 

The lower wishbone bolts to the same inner pivots as a standard Ram 1500, and the steering rack location and mounting (yellow) are the same, too. As you might expect, the extra 3 inches of suspension width per side also made it necessary to fit longer steering links (green).

Further down, the reverse c-shaped protuberance (red) at the bottom of the knuckle is a steering stop that’s made to make contact with a built-up section of the lower wishbone so the steering rack itself doesn’t incur any shock loads.

 

The Bilstein Blackhawks have a shock body with an outside diameter of 68mm, and they feature remote oil and nitrogen gas reservoirs (yellow) that are centrally mounted. The left and right sides are stacked on top of each other well above the skid plate, and they’re connected to the shock via beefy braided stainless steel hoses (green) that utilize a rigid stainless pipe for strain relief in the region where the hoses will hammer up and down with the suspension off road.

 

Please note the number at the top of the picture: 330mm. This is not the travel of the shock, but is instead the total wheel travel. That works out to 13 inches exactly, folks. That’s at least 4 inches more than a regular Ram 1500 and, more to the point, exactly the same as a Raptor.

These shocks are electronically controlled, with solenoid-controlled variable rebound and compression bypass circuits built into the piggyback housing (yellow). The main valving in the cylindrical shock body is arranged on either side of the main working piston like a monotube shock, but the variable damping mechanisms inside the piggyback are fed by oil in a concentric annulus that surrounds the main tube. That’s why you might see twin-tube in some written descriptions of this shock even though the primary valving is more like a monotube.

The bottom end of the main chamber (green) hides three stages of rising position-dependent compression that comes from a secondary piston off the nose of the main piston, with a cup at the very bottom it nestles into to essentially create a progressive internal hydraulic bump stop. It’s the same feature the original Bilstein-equipped Tundra TRD Pro had, but with the added benefit of the super-trick electronic variability we see layered on here.

Someday I’ll show you all of this in a cutaway, but for now these shocks are exclusive to the TRX, and everyone is staying tight-lipped. If I had to guess, and knowing that there is a tube-within-a-tube arrangement here to feed the adjustable valves in the piggyback chamber, I’d wager that the 68mm shock body contains a 46mm piston — a familiar Bilstein size.

 

Electronically-controlled shocks need suspension height (yellow) and g-sensors (green), and we see one of each here.

 

Don’t expect to bolt all of this onto your regular Ram 1500 and add flared fenders. The pivot points (yellow) for the upper control arm are some 2 inches higher than your non-TRX truck. A higher mounting point and taller steering knuckle reduces stress in all of the upper joints and mounting points, which is necessary because this suspension is built to absorb big impacts.

 

In case you were wondering, the lower control arm itself is the official jack point. Good thing, because my floor jack doesn’t have the reach to raise this long-travel beast by the frame.

 

Other views make the lower wishbone look bulbous and massive, but we can see that it’s a lot more weight- and stress-optimized from this shot I took while it was parked on my RTI ramp.

 

Looking from behind, the front stabilizer bar (yellow) is plain to see. It was located in front of the axle prior to the 2019 Ram 1500 redesign, but it was moved here because it’s more effective, easier to balance the forces because it’s opposite the coil over, and there’s more room to package it.

 

From here it looks as if the coil over is 65-to-70% of the way out from the inner pivot, so that is the shared spring and shock motion – with a modest deduction for its inward lean angle relative to the arm. The stabilizer link looks to be nearly dead center or maybe a bit outboard, so it’s in the 50% range. Engineers have to take these into account and make their springs, shocks and stabilizer bars stiffer in order to get the desired effect at the wheel.

 

Next to all that suspension beef, I wouldn’t blame you if you thought the brakes looked small. But they’re not. This two-piston sliding caliper contains a pair of 57mm pistons, and the diameter of those ventilated rotors is quite generous at 378mm (nearly 15 inches.)

 

Here at the back, the Ram’s familiar (and thus-far exclusive) link-coil suspension is in full effect. But look at those links! Get a load of that coil!

 

The coil springs have a preogressive rate design, and you can see that here. I talked to a Ram engineer about them, and he told me that they’re over two feet tall out of the truck. I believe it, because I measured 22 inches at the left rear at full droop in the ramp photo we saw earlier. That leaves a couple inches of preload so they don’t need retaining clips.

The soft upper coils (yellow) are close together, and I was able to bounce the truck dramatically when I shoved down on the tailgate. But you want a long spring with soft initial engagement if you’re, say, landing a jump. The lower coils (green) are farther apart and stiffer, and inside you can see the bump stop (red) and the witness mark where it makes contact at full compression.

Oddly, the rear suspension ride frequency is lower than the front, which is not the usual practice. You want the rear to catch up to the front after a single event so the vehicle levels out, and a higher rear stiffness does that. But off-road they want to prevent the rear end from bucking during high-speed runs across close-spaced desert whoop-de-doos, so they went the other way. I can feel the rear is different on a single dip-crossing just down my street, but they use the variable damping to compensate.

 

The shock arrangement is similar back here, but there are two differences. There’s no internal three-stage hydraulic compression bump stop inside because of the progressive spring and its bump stop. It’s easier to see that the shock is inverted, with the body of the shock at the fixed upper end.

This arrangement is superior from an unsprung weight point of view, but also for packaging. I followed the hose to find the remote reservoir (yellow) hidden behind the fender liner.

 

Like the front, the piggyback contains electronically-adjustable compression and rebound valving. Unlike the front, there are 355mm of wheel travel back here. That’s 14 inches, folks. The Raptor is listed as 13.9 inches. That’s a virtual tie – unless you’re a Ram fan. Is it weird that wheel travel is printed on the shock body? Yeah, but where else are you going to put that label?

 

The Bilstein Blackhawk’s stout 22mm shaft (yellow) has a hard chrome finish that you *do not* want dented up by flying stones – which there may be a lot of when you drop the hammer on 702 horsepower of Hellcat fury. That’s why they’re hidden behind these thick shaft guards (green), with a unique shape that gives them even more impact resistance.

 

The rear links (yellow) are not Ram 1500 carryovers. They are much longer and quite a bit stronger, and are more closely related to Ram 2500 pieces. That’s especially true of their pivot bushings (green) – though tuned differently for TRX, they are dimensionally identical to the high-angularity ones that are found in the Ram 2500 Power Wagon. The Power Wagon needs a suspension that articulates. So does this.

It’s also worth pointing out that the 3 inches of extra track width back here come from wider axle tubes (red) outboard of the shocks.

 

Link-coil suspension is more commonly called five-link suspension, and this Panhard bar (aka track bar) is that fifth link. The far end in the dim distance (yellow) is the fixed end that bolts to a bracket on the frame, while the near end (green) connects to a bracket on the axle tube.

But what’s that yellow thing (red – psych!) in the middle? Could it be a fifth shock absorber?

 

That’s exactly what it is. It spans between a bracket mounted atop the rear end housing and a barely-visible frame crossmember. It’s there to tame axle windup and power hop. This kind of this normally isn’t necessary with link-coil suspension, but there are 724 reasons why it makes sense here: 8 high-angularity suspension link bushings, 14 inches of rear travel and 702 horsepower.

 

This view gives you a better idea of where it is located. It also shows that there’s a bit to be gained by extending and re-routing the rear diff breather hose (yellow). As it sits, the “fording” depth here is 32 inches – same as the, um, Ford Raptor.

 

This may be the most stealthily awesome part of the rear suspension. You’re looking at a Dana 60 rear end (yellow) with full-floating axles. The Raptor as we know it does not have anything like it. I don’t know of any other “half-ton” truck with a full floater. What does that mean? The axle shafts are separate from the outer hub drive flanges. They’re splined and bolted together at the outer end. It’s a stronger setup that isn’t here for payload so much as hard landings crossed-up and high-speed impacts.

What you’re not seeing is a rear stabilizer bar. There are only bare unused holes (green). Apart from the TRX, all Rams with link-coil suspension have one. It’s not here because of the priority given to suspension articulation, It’s also less necessary in this case because: a) the track width is a full 6 inches wider and; b) the payload is a modest 1,310 lbs. That’s still a decent payload figure that bests the Raptor by 110 pounds.

What about towing? The TRX is good for 8,100 pounds. The Raptor crew cab is just a tick behind at 8,000 pounds. It’s almost as if someone was making sure they beat their rival by just a smidge all the way down the spec sheet.

 

The rear brakes are made up of 375mm (14.8-inch) ventilated discs and sliding calipers with a single 57mm piston. They have an electronic parking brake actuator, too, which I really appreciated when I set the brake and stepped (more like fell) out of the cab on my ramp.

 

These are massive LT325/65R18 tires – with a T-speed rating good for 118 mph, to boot. That works out to 35-inch tires in old money. The rims are 18×9-inches, and they feature a bolt-on beadlock-style aluminum trim ring that isn’t an actual beadlock because it doesn’t quite overlap (yellow) the tire sidewall.

The whole assembly weighs in at – get ready for this – 103.5 pounds. OK, the front one was 103 pounds. Still, it was very important for me to raise the truck as little as necessary so I could wrestle them on and off with minimal lifting.

 

Want to upgrade to a real beadlock? Mopar has you covered. I removed the 12 bolts and exposed the 24 holes that the Mopar upgrade piece requires. With those in place you can run ultra-low trail pressures and still keep the bead seated and prevent the tire from clocking itself when you give it a bootload of torque. Or you could still use these and paint them.

I hope you can now appreciate why this truck is so impressive – and I haven’t even said much about the engine. This is a well-executed off-road suspension with no cut corners, and the Ram engineering team has taken full advantage of the built-in advantage they had: link-coil suspension.

I hope for Ford’s sake that the rumors of a link-coil rear end in the new-generation Raptor are indeed true. It seems nearly certain that the new Tundra will have link-coil, and we can only hope that they step up and make a wide-track version of the Tundra TRD Pro to go up against the Raptor and TRX. It’s a good time to be a suspension nerd, is all I can say.

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 Edmunds.com (no relation) for 14 years.

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

 





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