Two thousand miles on Boss shocks and air bags
Those of you who’ve been following the progress on the JATAC know that we found the Toyota Tacoma’s factory suspension less than ideal. Spring rates front and rear were too high, resulting in a punishing ride over what I consider an acid test for a suspension: our driveway, comprising seven miles of dirt washboard and the nasty protruding rocks we call baby heads, bisected occasionally with diagonal rain-cut ditches. It brings out the worst in every vehicle that traverses it.
Yet the rear springs were not adequate to securely support the added weight of our Four Wheel Camper, which, when it was slid in at the FWC factory in California, dropped the tops of the rear fender cutouts (a standard spot to measure differences in ride height) a good four inches and left the truck nose-high. Since I’d been virtually certain this would be the case, I brought along a set of Australian-made Boss air bags and installed them at the FWC factory. That levelled the truck nicely, but the trip home made it clear the factory shocks were now sorely overmatched.
My first attempt at optimizing the Tacoma’s suspension to ensure safe handling, predictable off-pavement capability, and a reasonably compliant ride, involved the installation of an Icon Vehicle Dynamics suspension kit, comprising pre-assembled front cartridges with adjustable ride height (left stock), Icon springs, and Icon adjustable remote-reservoir shocks, plus a pair of Icon adjustable remote-reservoir rear shocks.
The Icon shocks are superbly constructed and fully rebuildable. The valving can be custom-calibrated for specific applications, and I requested heavier valving for the rear. However, I believe the request was lost as the shocks failed to control rear-axle bounce even at their top setting. Shipped back to Icon, they were returned in short order and felt infinitely better, displaying excellent sway, roll, and bounce control at half setting.
Unfortunately the front cartridges proved to be less than ideal for our situation. The Icon springs are 20 percent stiffer than stock (which you’ll recall I already thought too stiff). Although we planned to install an after market bumper and winch, the bumper was to be a very lightweight prototype aluminum unit, and the Warn 9.5 XP winch, with Viking synthetic line, would weigh less than 70 pounds. I was convinced this wouldn’t be enough to attenuate the harshness of the Icons. (If we’d planned to install a steel bumper such as an ARB the situation might have been diferent.) I checked with Icon but was told that the stock Toyota springs would not fit their struts.
An additional factor in my decision-making process was the fact that the Icon shocks employ heim-joint connections at the bottom of the shafts. Heim joints dispense with rubber or polyurethane bushings in favor of an all-metal spherical joint. The result is very precise control and noticeably quicker handling, but a slight increase in harshness—and we were already dealing with too much of that. Lastly, the unprotected—albeit heavily chrome-plated—shafts of the shocks had me concerned from the start that they would eventually be subject to micro-pitting from road debris, especially in the rear.
My conclusion regarding the Icon suspension was that it was a very high-quality system oriented more toward high-performance use than slogging along at overlanding speeds with a camper attached. Fortunately I located a fellow overlander who owns a late-model 4Runner, who was interested in upgrading his OME suspension. He reported favorably on his initial drive with the Icons in place, and has promised to send me a followup after putting a few thousand miles on the truck.
In the meantime, Reece Tasker of Boss Global sent me a set of Australian-made Boss front shock cartridges—which, like the Icons, are height-adjustable but which can use the stock springs—and a pair of rear shocks. (I’ve detailed Boss shock technology here.) The increase in compliance at the front of the truck was instantly apparent, and with the 12-step adjustments of the Boss shocks set at 3 in the front and 5 in the rear, it was clear there was plenty of room to tweak damping in either direction. A month later, with the prototype bumper and winch in place, I clicked the front shocks up one notch, and we left to help lead 12 vehicles along the Continental Divide from New Mexico to Wyoming.
Two thousand miles of highway, smooth dirt road, washboard, and rock-strewn four-wheel-drive tracks later, Roseann and I both pronounced ourselves happy with the new setup. The added weight of the bumper and winch attenuated the firmness of the front springs to the point they felt decently compliant, while retaining good road manners. The shocks had no problem controlling either end of the truck, and they were so easy to adjust that I found myself backing off a notch on days that were all off-pavement, then clicking them back up for highway transits.
We did experience one unforeseen issue after all those miles. After returning home, I noticed the right rear air bag losing pressure gradually day to day. I checked all the push-to-fit pneumatic couplings in the system—not an idle task given the numerous T-junctions connecting the hard-mount compressor, dual-function gauge, bleed valves, and bags—but the leaking continued. Given the overbuilt nature of the Boss air bags I doubted it could be the bag itself, but I was stumped.
The right (green, as in starboard on a boat) needle began falling slowly after the Continental Divide trip.
Then, on a drive back from town, Roseann drove over a cross-axle ditch that flexed the suspension significantly, and when she hit a mild bump shortly after that the right rear spring bottomed with a thump. I looked under the truck and found the right bag completely deflated. Had it blown? We limped home, I filled the bag again with the truck parked, and . . . it held air just fine, displaying only the slow leak. The next day I drove the truck to test it, and after the first spot in the road where the suspension flexed, whump—the bag was dead flat again. Crikey.
Finally I crawled under the truck and checked the bag assembly itself—and found that three of the six countersunk bolts that hold the base ring of the bag to the base plate were completely missing, and another was backing out rapidly. All became clear: As long as weight was on the bag, the bottom seal bled air slowly through the gap. But when that side of the axle dropped into a deep enough depression, the bottom of the bag pulled clear of the base by a fraction of an inch, and whoosh, out went all the pressure. Ironically, the opposite bag, which wasn’t leaking, had just two of six bolts remaining, fortuitously on opposite sides of the base.
Yikes
I replaced the bolts, secured them with blue Loctite, and the leak vanished. (Reece Tasker of Boss Global informed me that the company has since switched to standard hex-head bolts with lock washers to secure the base plate.)
So, two years plus since we mounted the Four Wheel Camper on the Tacoma, the suspension is finally working as it should. I’m still thinking that the ultimate rear setup for the JATAC or a similar truck—given that we leave the camper on all the time—would be a set of custom leaf springs that would support the weight of the empty camper to achieve a level, compliant ride, with the Boss air bags inflated to just a few PSI. We could then add pressure as needed when we load the camper with water, food, and all our kit. For someone who prefers to remove the camper between trips, the combination of adjustable shocks, stock leaf springs, and air bags allows you to compensate for the vast difference between a loaded and empty truck bed, while retaining safe handling and a comfortable ride in either situation.
