BILSTEIN B16 (PSS9) COILVOVER KIT FOR PORSCHE BOXSTER/CAYMAN 986/987 48-347723

Street / Track (without PASM)

The 987 Boxster and Cayman already have an excellent chassis, so the goal with the B16 isn't to turn the car into something completely different. It's to add more spring and damping control, useful ride-height adjustment and enough tuning range for someone who still drives the car regularly on the street but also wants to autocross or spend some time at HPDEs and track days.

The standard setup uses a 289 lb/in linear front main spring, 114 lb/in front tender spring and 371 lb/in progressive rear spring. Those are still relatively street-friendly rates, which is an important part of how we view this kit. On the softer damping settings the car can remain comfortable enough for regular road use, while the adjustment gives you room to add support when you're driving harder.

Adjustable damping

The PSS9 gives you nine damping settings, making it easy to run the car softer on normal roads and add damping when grip and chassis loads increase at an event.

For a street-driven 987 on the tire we recommend, the Michelin Pilot Sport 4S, the standard spring and damper package is very well matched. It also gives someone starting to explore autocross or track driving enough adjustment to make useful changes without requiring a complicated motorsport damper.

There is a limit to that. If the car starts moving toward very wide Super 200 tires, R-compounds, fixed seats, a roll bar and regular serious track use, the standard spring rates and valving are no longer where we'd want to be. The dampers can be revalved and combined with higher spring rates by a competent tuner, but out of the box this is a Street / Track suspension, not a Clubsport package.

Inverted monotube construction

One of the things we particularly like about this application is the damper construction. The B16 uses inverted, shaft-down monotube dampers at all four corners, with the front operating as a true inverted strut.

The larger outer structure carries the suspension loads while the smaller internal piston rod does the damping work. That makes for a very rigid assembly and helps keep side loading and friction away from the internal damper components. The smaller internal shaft also reduces the amount of gas force trying to extend the damper, which is something we like. The spring should provide the spring force while the damper controls motion.

The shaft-down layout at the rear also keeps more of the damper mass attached to the chassis rather than moving with the wheel. The tradeoff is that the damping adjusters are located at the bottom, so access isn't quite as convenient as a top-mounted adjuster. We think that's worth it for the structural rigidity, low-friction operation and durability of the design.

1W/car Setup Recommendation

For the 987, our ride-height reference is the Cayman R — approximately 20 mm lower than a standard Cayman.

We think Porsche got that height right. It lowers the center of gravity and gives the car the stance it should have while still retaining useful bump and droop travel. The B16 can achieve that height comfortably, so there is no reason to use the rest of the lowering range simply because it's available.

This is not a particularly stiff suspension, and that's part of why it works so well on the street. It also means we don't recommend slamming the car. If you want to run substantially lower than Cayman R height, you need a different suspension strategy with more spring rate and stronger damping, particularly compression damping, to properly control the reduced travel.

For tires, our recommendation is the Michelin Pilot Sport 4S. That's the tire we use as the reference point for this type of street-performance 987. It gives the car the grip, response and road manners that fit the suspension without pushing the chassis into the much higher loads associated with a serious track tire.

Top mounts and camber

For the use case we recommend with this suspension, we generally prefer the factory Porsche rubber upper mounts. They're durable, well made and keep unnecessary noise and vibration out of the chassis.

We'd use the available factory suspension adjustment for camber before automatically adding spherical top mounts. That's especially true at the rear, where the mounts are located very close to the occupants and a solid or monoball connection can add a surprising amount of NVH.

If the car becomes more track focused and additional front camber is needed, a properly designed GT3-style front upper mount or similar high-quality solution can make sense. At that point we're also probably discussing more tire, more spring rate and less street use. For the normal B16 customer, we prefer the OE rubber mounts and the refinement Porsche engineered into them.

Track progression

The B16 is a very good suspension for someone beginning to explore track driving, but we don't want to pretend the nine-position adjuster makes it appropriate for every tire and spring combination.

As tire grip increases, the loads going into the suspension increase with it. At some point the car needs more spring rate and a different damping calibration rather than simply turning the shocks firmer.

If you're heading toward a more serious track build, talk to us before adding more tire, spring rate or sway bar. There may be room to develop the B16 farther through spring changes and revalving, or it may make more sense to move to a more track-focused damper.

Our goal is to make the fewest changes necessary to get the result you're after, not to keep adding parts because they're available.

Why we trust BILSTEIN

BILSTEIN has decades of experience in OE suspension development and motorsport, and that matters on a Porsche that was already extremely well engineered from the factory. We don't assume an aftermarket component is an improvement just because it's lower, stiffer or has more adjustment.

The B16 earns its place because the basic engineering is there: monotube construction, inverted dampers, matched springs, application-specific valving and the durability we'd expect from a major suspension manufacturer.

It's more expensive than many coilovers available for a 987, but we'd rather see someone buy a well-developed suspension once than save money on a kit that compromises the car they're trying to improve.

For a 987 that still sees real street mileage but also gets used for autocrosses and occasional track days, this is exactly where we think the B16 PSS9 belongs.