I've had the opportunity to put about 100 miles on the Bilstein B6 HD shocks that I purchased for my 2012 Cruze Eco MT6, and feel that I can give a good review. For those who are unfamiliar with these, Bilstein has three shock replacement options for the Cruze; the Bilstein B4 (OE Replacements), Bilstein B6 HD (a heavy duty shock), and the Bilstein B8 (a heavy duty shock designed to be used with lowering springs). Since I have no desire to reduce my ride height with the roads we have around here but did want to upgrade, I went with the Bilstein B6 HD.
The reason I began looking for a replacement set of shocks is that I began to notice a degradation in vehicle stability and comfort. When driving over a highway overpass, for example, I'd hit uneven pavement that sometimes had lane-wide gaps or bumps, and the suspension in the front would bottom out. Most people might not notice what I did, but when the shocks crash through the jounce bumpers, you can definitely notice it happening. On a particular road I always travel to buy car parts, there's a railroad track which everyone slows down on. In the Cruze, I would bottom out the front suspension very noticeably at the posted 35mph speed limit. It was unnerving. Furthermore, when turning over uneven pavement, the vehicle would rock left and right a bit, but overshoot the simple uneven pavement in an attempt to stabilize itself. Braking exhibited more nose dive than usual as well.
This could be written off as worn shocks, and some of it undoubtedly is. I have 66k miles on the vehicle now, with about 50k miles on the actual shocks (they were replaced by GM under warranty due to noise early on), but my shocks at 50k miles did not exhibit any of the typical symptoms that "completely worn" shocks do. It is generally stable on the highway (doesn't "float,"), and rides comfortably.
The Visual Difference
An immediate difference can be seen visually in the shocks. The Bilstein shock is longer, and contains a built-in jounce bumper in the shock itself, so you need to remove yours when installing. This does not affect ride height. The strut shaft is MUCH larger in diameter.
The rears were not as big of a difference, measuring a shaft diameter of 12mm stock and 14mm on the Bilsteins, but it is still an increase nonetheless.
Aside from the obvious visual differences, the vehicle maintained the same front ride height, but gained about 1/2" of ride height in the rear. I've read about this happening with other cars, as this is a pressurized gas shock. Since I have a sound system in the trunk, I don't mind the increase at all and expect it to settle a little over time.
The Driving Difference
The initial driving experience was nothing short of remarkable. I had read other reviews people posted of these shocks on other vehicles where the vehicle was described as "taut," and I think that term defines the change quite accurately. The vehicle simply feels more composed, more controlled, more predictable, and more stable.
I have a couple of places where I bottom out the suspension on a regular basis. The first is the railroad tracks mentioned above, and the second is a transition between two surfaces going over a highway overpass. First thing I did once I installed these is go out for a drive on those same surfaces. The highway transition was such a big difference that I didn't even notice it. When I approached the railroad tracks, I felt a little crazy since everyone was slowing down to 25mph in the 35mph zone, and I was accelerating to 40mph. Went over the railroad tracks and barely felt it. The car didn't have the usual nosedive, slam on the jounce bumpers, bounce back up, and level off again. It just kind of rolled over the uneven pavement as if I was driving on a cloud.
This all came as a surprise because on lighter irregularities in the road, the suspension now feels more sporty. Instead of calling it stiff, I'd refer back to the "taut" reference. While you certainly feel more of the road with these shocks than with OE shocks, you feel less of that road on large anomalies, and even the small road anomalies aren't what I'd call "stiff." On the highway, your bead isn't bouncing back and forth as if the suspension was welded; it simply follows the road more securely as if there was some magnetic force pulling the car to the road. That is, until you hit a big hole or bump in the ground and the car just gracefully absorbs it without making you cringe.
I was very deliberate in not wanting to lower the car. I like how cars feel more planted due to the reduction in body sway, but don't like the harshness you get with the reduction in suspension travel. I feel that with these shocks, I got every bit of sporty handling one would out of lowering springs, but without all the harshness.
On a scientific level, the purpose of the shocks is to control suspension travel; the purpose of the springs is to suspend your vehicle's weight. These shocks more strongly limit suspension travel, so you feel more of the small bumps on the road instead of the suspension absorbing them, but in return, the suspension doesn't bottom out and make you wish you'd have slammed on the brakes earlier when going over much larger bumps in the road. The result is almost an oxymoron; sporty, but comfortable; taut. I felt like I was driving a tuned European car.
On braking, I had 1/3 the amount of nose dive I used to, and it was much more gradual than before. While making quick turning maneuvers, there was less body sway, and the vehicle responded to drive input more quickly and more accurately. Going over uneven pavement while turning, when my Cruze used to rock left and right trying to settle back to a resting position, the shocks kept the vehicle riding level and stable. All in all, the vehicle feels much more confident.
I'll admit, this is the first time I've owned a vehicle that had a truly good set of shocks, so it was a bit of a revelation for me, but I can wholeheardly give this upgrade a solid recommendation for anyone looking to improve the ride comfort of their vehicle without turning it into a land yacht, and improve the handling of their vehicle without clenching their buttocks whenever they see a large bump or pothole in the road.
The Bilstein B6 HD shocks are an all-around solid upgrade for the Gen1 Chevy Cruze and will be my go-to replacement shock for any vehicle I own in the future. For those of you with lowered springs, look into the B8 shocks.
Both the Bilstein B6 HD and the Bilstein B8 shocks are available from order from the BNR Website:
B6 HD: Bilstein B6 HD Shocks
B8 Sport: Bilstein B8 Sport Shocks