The Summit Racing website has more than 12,000 listings for shock absorbers. The selection ranges from simple hydraulic shocks to gas-charged, single- and double-adjustable, off-road, and specialized racing shocks for circle track, drag racing, and road racing.

One of the shock brands offered by Summit Racing is Bilstein. The German company’s claim to fame is the development of the gas-pressurized monotube shock. Unlike traditional twin-tube shock absorbers that many of our favorite classic American rides came with, the monotube design has a large single cylinder that holds hydraulic oil and nitrogen gas in separate chambers with a floating piston valve between the two. The benefits are twofold:

• More efficient heat dissipation from the hydraulic oil
• Gas pressure on the floating piston for less oil aeration (foaming) and viscosity loss

Bottom line, a Bilstein monotube shock retains full damping characteristics under all conditions, is less prone to fade due to heat buildup, and has a longer lifespan than a twin-tube shock. The pressurized gas also eliminates the ‘floaty’ feel unpressurized twin-tube shocks can get when air bubbles form in the hydraulic oil from hard use.

You can learn more about how monotube shocks work in this Bilstein video.

I recently decided to replace the vintage Delco shocks on my 1971 Corvette with Bilsteins. This required a little detective work and a bit of an installation learning curve on my part. Let’s dig in.

Choosing the Right Bilstein Shock

For street-driven performance cars, Bilstein offers the B6 and B8 Series shocks. Both are OEM replacement-type shocks. According to Bilstein, the main difference between the two is the B8s have a shorter travel for use with lowering springs and larger sway bars. There are people that say the B8 shocks have stiffer valving to compensate for their shorter travel. That would make sense, but I could not find anything from Bilstein that lists different valving between the two. 

There are some applications where you might choose to mix and match B6 and B8 shocks.  My  Corvette is a good example. I have a set of 550-pound front springs and a 360-pound composite rear spring. The front springs are much stiffer and shorter than the OEM baseline springs. The composite rear spring acts “softer” than its steel multi-leaf spring counterparts. The general consensus in the Corvette community is that with this particular combination, use B8 shocks on the back and B6s on the front. If you have a stock-type suspension with a steel rear spring, put B6s on all four corners.

Installation

Bilstein arranges the front shock upper mount hardware differently than OEM. For the Corvette, the OEM hardware arrangement order is washer-bushings-washer-attachment nut. For the Bilstein, it’s washer-bushing-washer-bushing-washer-attachment nut. The second washer for the Bilstein shock is machined with a recess in the center hole. The shock shaft is machined for and fitted with a wire C-clip. The C-clip rests in that recess. There’s no mixing up the washers because only one has the recess.

The Bilstein shock has no flat to hold when tightening down the attachment nut. Instead, the shaft is machined to accept a 5mm Allen wrench. This is actually a cleaner arrangement than the standard flats found on most OEM or replacement shocks.

At the bottom of the shock, you’ll find the T-bar mount is closed, not U-shaped.  That’s good news, because it’s not uncommon to find a shock that is either improperly installed or has shifted to one side right through the open U-shape. The slotted, closed configuration of the Bilstein shocks solves that dilemma.

Bilstein seems to use bushings that have a harder durometer than an OEM shock bushing. Finally, the dust cover on specific Bilstein shocks like my Corvette’s rear shocks is made from a soft plastic instead of metal.  

I haven’t had a chance to see how the Bilstein shocks perform as I’m in the process of redoing the Corvette from top to bottom. But I can show you how to install them in the accompanying photos.

Bilstein shocks for C3 Corvette
Bilstein shocks are a monotube, gas-charged design. That means the body of the shock absorber functions as a cylinder that carries both hydraulic oil and gas (usually nitrogen) and the piston valve. A floating piston separates the oil chamber from the gas chamber. The design means Bilstein shocks are less prone to fade due to heat buildup and don’t have the ‘floaty’ feel unpressurized twin-tube shocks can get when air bubbles form in the hydraulic oil from hard use. A monotube gas shock will create a stiffer ride than a purely hydraulic one, but the handling will be much crisper. (Image/Wayne Scraba)
Bilstein B6 Series front shock for C3 Corvette
This is a Bilstein B6 Series front shock for C3 Corvettes. Often referred to as the Heavy Duty Series, the B6 are OE replacement shocks designed for use with stock-height springs and provides a good balance of damping for better handling and good ride comfort. (Image/Wayne Scraba)
Bilstein B8 rear shock for C3 Corvette
This is a Bilstein B8 Series rear shock for the Corvette. Folks often call the B8 the Performance Series. They have a shorter travel for use with lowering springs and/or larger sway bars. They also offer better control and a firmer ride than B6 shocks. Though Bilstein does not specifically mention it, more than a few Corvette owners think the B8 shocks for C2 and C3 Corvettes are as much as 30 percent stiffer than the B6s. (Image/Wayne Scraba)
Delco and Bilstein rear shocks for C3 Corvette
Compare the vintage (cosmetically restored) Delco rear shock on the left versus the Bilstein. The Bilstein is marginally shorter, but keep in mind that most cars only use a fraction of the overall shock stroke. Same goes for the rear shocks. (Image/Wayne Scraba)
Front shock hardware for C3 Corvette
Mounting hardware for the front shocks is where things get interesting. On the left is the top mount hardware for a stock-style replacement shock. On the right is the hardware for a Bilstein shock with an extra washer. (Image/Wayne Scraba)
Washer on Bilstein B6 front shock for C3 Corvette
This is the extra washer installed on one of the B6 front shocks. It is machined with a recess in the center hole; a wire C-clip on the shock’s shaft fits into the recess. (Image/Wayne Scraba)
Top mount hardware for Bilstein B6 front shock for C3 Corvette
Here is the top mount hardware installed on the Bilstein shock. The shaft is machined to accept a 5mm Allen wrench. The nut is a metric Nyloc type. If you chose to torque the nut to spec, use a crowfoot extension on your torque wrench while holding the shaft in place with the Allen wrench. (Image/Wayne Scraba)
Delco and Bilstein front shock lower T-bar mounts
Here’s a comparison of the bottom tie bar arrangements. The slotted and enclosed setup on the Bilstein at the right is more secure than the slotted T-bar found on many stock shocks. (Image/Wayne Scraba)
Bushing for Bilstein B8 rear shock for C3 Corvette
The Bilstein B8 rear shocks have bushings made from a harder durometer material than bushings used on OEM shock absorbers. The stiffer bushings don’t deflect as much as the softer stock bushings, which improves shock performance. (Image/Wayne Scraba)
Bilstein B8 rear shocks on C3 Corvette
Here are the Bilstein B8 rear shocks installed on my Corvette. Note the composite rear spring. It is much lighter and has a higher spring rate than a multi-leaf steel spring. Many C3 Corvette owners use B8 Series shocks with a composite spring to better control the ‘bounciness’ the spring can have with a softer shock. If you have a stock-type steel rear spring, Bilstein B6 Series shocks are recommended. (Image/Wayne Scraba)
Keywords
C3 Corvette , shocks
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Author: Wayne Scraba

Wayne Scraba is a diehard car guy and regular contributor to OnAllCylinders. He’s owned his own speed shop, built race cars, street rods, and custom motorcycles, and restored muscle cars. He’s authored five how-to books and written over 4,500 tech articles that have appeared in sixty different high performance automotive, motorcycle and aviation magazines worldwide.