Testing Bilstein 6112 Big-Piston Coilovers for Light Truck IFS

Oversized 6112s offer solid off-road damping with no reservoirs or rebuilds.

May. 16, 2018 By Justin Fort. Photos by Justin Fort and Bilstein.

Some of the best solutions aren't new, they're just innovative. Take the Bilstein 6112. A few years back, the light-truck engineers at the Bilstein facility in Poway, Calif., first saw the company's prototypes for a heavy-truck coilover. They recognized the same design could also be a solution for off-road use on independently suspended trucks, and started testing.

Engineers shoehorned the 6112 into every application possible. Oversized shock body and factory-OD coils mean you'll need the right spring compressor.

"We got a hold of one of the preproduction 60mm-piston heavy-truck units and made a new shock with it for an FJ Cruiser," stated Shane Casad, Light Truck and Off-Road Product Manager. "When we got these shocks on it, the performance was awesome. Mind-blowing stuff, right off the bench. The ride was great, the damping was right in range. They took a beating without overheating - we couldn't find their limit. They worked so well that we took over the assembly line, and now we have these for every half-ton vehicle that has a coilover in the front."

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"Lots of other companies build and sell these big 2.5-inch billet things in relatively small numbers. We could offer comparable suspension management within a production 65mm unit. It was an awesome opportunity - corporate couldn't say no."

Off-Road.com's evaluation of the 6112 was done back-to-back with a standard-diameter shock on a third-generation 4Runner equipped with 285/75/17s Nitto Trail Grapplers. The 6112s displayed a noticeable increase in smoothness, especially at speed, and improved per-event cushioning significantly. Impact harshness in whoops was reduced. Especially noteworthy was the improvement in damping at high speed on unmaintained trail and resulting steering control. The initial softness of the 6112s did increase nose-in body roll on paved streets, however.

The oversize shock body requires attention be paid to nearby parts. The lower clevis for the limiting strap needed to be pushed out about 5mm on the lower shock bolt.

Right-Sized Can Be Right-Priced

One of the design elements that made the prototype 6112 an easy fit for independently-suspended light trucks was stroke length. 99 percent of IFS-equipped trucks that roam the land - everything from an F-150 and 1500 to the Taco and XTerra - have a relatively short shock stroke (full stuff to full droop). The 6112 was designed for that short stroke, and doesn't waste extra shaft or body on dead travel. Its original specs also offered the massive fluid capacity of a 60mm piston designed for big-truck use despite the abbreviated suspension action.

Another factor that attracted the Bilstein boys to adapting a big-truck shock to smaller consumer-sized rigs was a hole in the marketplace: the price-point for their non-reservoir coilover would land between a mild street/off-road 40 or 50mm shock and the high-zoot long-travel billet-aluminum pieces on the market, even when made in the U.S. of A.

Bilstein includes necessary hardware with 6112s (nice hardware) except for the isolator, top hat and upper bushings, which are reused OE bits. Factory-quality matters.

"Shoppers were either spending $200-300 for something like a 5100," continued Casad. "... or dropping $1200 on two long-travel units that they might only use a half of. We're right in the sweet spot with the 6112 - a set costs about $650, and it's still a bolt-on."

Casad admitted to specifically targeting type of 'froaders who are in it for performance, and either don't care about appearance or who couldn't justify spending $1200 on shocks for a $2000 truck. "Cause and effect, not bling."

Simple to Install at Factory Mounting Points

A slice of the equation that might go unappreciated is the reuse of the OE-spec cushioning provided by factory mounting points and isolators: a 6112 deploys using the stock upper shock bucket, isolator and an OE-style vulcanized lower bushing. All of these bits are factory-durable, improve the lifespan of parallel components, are easy to replace, and keep shock activity as isolated from the chassis as possible (quieting your truck, especially versus heim joints).

In the case of our gen-three 4Runner, we had backup top-hats and a spare set of isolators. It's wise to keep an extra set handy if you're modifying for off-road.

"The 6112 isn't designed to be cheaper, but it will cost less to operate - these aren't 'budget'," insisted Casad. "Because Bilstein was going to build these for military and heavy-truck applications, it was a great design. We were able to reset the product line for light-truck use and hit a vacancy in the marketplace."

Built for Heavy Truck = Easy Life on Light Truck

The 6112's big 65mm body (escorting the 18mm shaft up and down) means the 60mm piston has more real estate for valving, which enables smoother initial cushioning and expanded capability to damp at higher speed (both at impact and mid-stroke). Of course, the 6112 isn't a reservoir shock, which has just that - a reservoir -holding more fluid than even the big-body 6112.

Speaking of Toyota, many folks miss that there's a formed washer pressed into the bottom of the top-hat. This is one of the two that bookend the lower bushing.

"Our 5100s have a reputation for being durable, but in comparison, the 6112 is a tank," added Casad. "Compared to Bilstein's 5100 - it's a good reference point, as everyone's run a set at some point - the 6112 has more oil and can offer a lot more damping, and the 65mm tube means there's a lot of room for oil to move and grow. It's just good physics. The bigger body also makes excellent use of Bilstein's monotube technology because there's even more room for the internal gas chamber to expand and contract. They're very well designed.

Casad relayed a story about what he's been telling potential 6112 customers. "Pre-runner guys like the 6112, but because they're not owner-rebuildable, these guys don't seem to understand them - they expect to take 'em apart every 10,000 or 1000 or 40 miles. So you have these hard-hitting desert Tacoma and Ranger guys thinking that after a hard run the 6112s will be worn out, but they don't wear out; plus, they've got a lifetime warranty. They don't require any maintenance. Bilstein doesn't expect you to wear them out."

Visit https://www.bilstein.com/us/en/ for more information on these shocks.


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