The "shop" vehicle, a 2017 Pilot EX-L AWD is frequently used for towing. Our favorite trailer is a BigTex 70DM that weighs about 2,200 lbs, and it is frequently used to haul Hondas (as you might expect) that weigh 2,800 lbs or so. As such, with 500 lbs of tongue weight, even though the Pilot can handle 5,000 lbs of towing capacity... it suffers from a fair bit of squat (about 1").
After disassembling the factory shock/spring assembly, we found a spring that has a rate of about 260 lb/in, which explains this squat. These springs are fairly soft for a vehicle with a curb weight greater than 4,000 lbs, especially one that tows. This also helps explain why we've also noticed that the Pilot, while it has a great ride around town, seems to be a bit soft on undulating bumps on the highway (when loaded with gear).
After a bit of searching, it seems that there are really no options for upgraded or adjustable shocks for this chassis, and further, the coil-over rear shock/spring design makes an external airbag more than a little complicated.
Not ever having met a coilover we couldn't design, we got to work on engineering a solution.
The design of the factory coilover is very similar to others that Honda has made in the past. The most unique challenge is that the extended top-hat and large diameter spring mean that a long shock body needs to be used, as well as a large diameter hat adapter to hold a standard 2.5" diameter coilover spring in place.
We selected a QA1 DS702 shock. While this shock is a dual eyelet design (the stock has en eyelet on the bottom and a stud on the top), they sell several adapter kits to convert the top eye to a stud. Using their SS110SDM stud top conversion kit, the free length matched the stock shock body very closely. This stud top conversion kit also comes with isolator rubber that closely matches the stock parts, and works with the stock top hat.
The stock lower shock bolt is an 18 mm bolt. This is much larger in diameter than most aftermarket shocks are designed to take. Fortunately, the QA1 shock comes with a center bushing that will fit a 16 mm bolt, and Timesert makes a variety of 16 mm inserts that will thread into an 18 mm hole. This allows us to use a 16 mm bolt, but still easily remove the bolt and convert back to stock if ever needed. The QA1 shock is much narrower than the stock shock, but this is cured with a few custom spacers.
The stock spring was very close to 12" in free length, making it fairly easy to use a 12" long, 2.5" ID coilover spring. We selected a 450 lb/in spring to help reduce the ~1" of squat with the loaded trailer to about 0.5" of squat. As mentioned, the stock spring is much larger in diameter, so we designed and prototyped a top hat adapter to center the spring inside the stock top hat (keeping the stock spring isolator).
Installation is very easy as far as coilover installs go. 3 bolts hold the top hat into the body, and all 3 are easily accessible with the wheel removed. The lower shock bolt is easy to get to, which is good, considering it requires around 120 ft lbs of torque to loosen it. To get clearance to free the shock, the lower arm bolt that holds it to the knuckle needs to be removed, and the whole assembly can be removed. All of this can be done without disturbing the alignment, although it will need to be checked/adjusted if the ride height is changed.
For our setup, we chose to raise the ride height 0.5" in the back, to help allow for squat when loaded with the trailer. As expected, not only did this work as planned, the affect on ride and handling as a result of the "lift" was unnoticeable. On the street, you can tell that the rear suspension is slightly stiffer, but it still feels comfortable. When loaded with the trailer, the ride feels stock "ish" (softer, but not too uncomfortably so).
We set the shocks to 9 clicks above full soft after some experimentation. Much softer and the ride was a bit bouncy, much stiffer and it was a bit jarring.
In all this modification made the Pilot feel like we think it probably should have from the factory, and behave more like it needed too when loaded with the trailer or gear.