Introducing the new EM46 Series Shock For Late Model Racers

April 26, 2022 4 min read

The EM46 Series may be referred to as an “air shock” by a lot of people in the racing industry; but what is it really, how does it work, and how will it make me faster?

What is the purpose of a shock absorber? 

The primary purpose of a shock absorber is to minimize or even eliminate the oscillation inherent in the cars springs. By eliminating as much spring oscillation as possible we maximize the available traction where the tire contacts the racing surface.

What is an “air shock?” 

There is no such thing as an “air shock” because the products circulating pit row contain no air, at BILSTEIN we recognize the term “air shock” is a misnomer. A more accurate label for a product that performs like this would be an “air spring,” as found in our B4 OE (Air) suspension modules.

The new BILSTEIN EM46 shock combines the elements of both spring rate and shock damping into the same product.

How do we achieve this?

The EM46 is a BILSTEIN 46mm steel shock body utilizing a 22mm diameter rod, shock oil, and a nitrogen gas charge. The purpose of the product is to generate spring rate in order to eliminate the spring from the corner of the car. No spring, means no spring oscillation, translating into maximum grip for the tire on that corner of the car.

The nitrogen gas charge is “emulsified” into the oil under high pressure. Compression and rebound damping forces are tuned to control how quickly the rod can move in either direction. For example if we used an EM46 on the right front of a circle-track racecar we would likely use a soft compression valving and a stiff rebound valving; and if we used it on the left rear of a dirt late model we’d likely use a stiff compression valving and a soft rebound.

The 22mm rod compresses the oil when it enters the shock tube and generates spring rate. The spring rate is controlled and tuned by the amount of oil in the tube versus the nitrogen gas charge emulsified into the oil.

How does the EM46 produce a performance advantage?  The EM46 eliminates spring oscillation entirely by eliminating the steel spring and the inherent oscillation. Compression of oil in a cylinder produces spring rate but there is only miniscule oscillation in the “oil spring.” On the left rear of a dirt late model, the EM46 helps raise the left rear of the car “on the gas” and gets the rear deck and spoiler up into the air flow producing more downforce quickly.

Tuning your EM46 requires some information about your car. 

In the case of a left rear shock on a dirt late model we would need to know the center to center dimension of the shock/spring combination on that corner of the car at static ride height and the static ride height spring load. We would also need the center to center dimension of the shock at full droop, and also the spring load.

Knowing these factors, the EM46 can be built to the spring load you need at static ride height and droop height using the right combination of oil fill level and nitrogen charge pressure.

When using the EM46 on any other corner of the car we’d need to know static ride height center to center dimension, and spring load. Unlike the left rear of the dirt car application, we’d need to know the center to center dimension at full compression and the spring load at full compression.

The full scope of applications of this type spring/shock product has not yet been explored.  To date we have seen performance gains using this product on the left rear of dirt late models, right rear of late models on asphalt and dirt, right front on asphalt late models, and on the “lift bar” (torque arm) on dirt late models.

The advantage of the EM46 over other “air shock” type products on the market is extreme durability, consistency, and tunability.

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