Ever since Penske was selected as the supplier for shock absorbers for Spec Miata several months ago, the company has been working at a feverish pace to produce something reliable and robust for the most widely road-raced car in the United States.
With the intention of improving predictability and consistency, they implemented all the typical features they’re known for—a nice bore finish, a good piston design, and strong seal—and put it through the ringer in testing. The result are dampers that are well-suited for the application.
Discoveries in Testing
Though not a massive redesign, the dampers feature improvements in several less-obvious areas to make better suited for long, harsh seasons. Much of the focus was placed on eliminating continuous compression on the bump stop, thereby reducing wear and tear on other components and increasing reliability of the parts.
Increase in Shock Travel
Though it was never intended during the R&D process, Penske also managed to increase shock travel—the travel to the bump stop when measured at ride height increased over the Bilstein units they replace by more than one inch in both front and rear positions.
In developing these new shocks, they determined that a raised upper mount could allow for more travel, but the physical limitations of the chassis could marginalize actual travel gains. This meant the raised upper mount was not developed to increase rear suspension travel because the rear upper control arm would have metal-to-metal contact with the rear subframe—only to be compounded by the tire contacting the wheel well.
For more information on the technical details regarding shock travel and bump stop performance, read here.
Maximizing Bump Rubbers
The bump rubber provides a plush cushion at the end of shock travel. With the integration of a Delrin shaft spacer against the top mount, abutting a polyurethane bump rubber at the top of the shock body, violent chassis disruption was avoided.
Developed on the Penske Technology Group 7-post shaker rig
By utilizing the 7-post Penske Technology Group dynamic shaker rig, the engineers were able to determine how unsettled the car became when hitting the bump stops. See the video below for a demonstration of curb strike and the effect it has on the stability of the car. Clearly, keeping the suspension working within its intended range does wonders for stability.
Usage in the Future
For this year, this new shock will be eligible at any level of SCCA and NASA Spec Miata competition. For 2020, it will become mandatory at Championship and Majors Tour events. The response from racers at the first test, held at Carolina Motorsports Park, was overwhelmingly successful—an auspicious start to a new development from one of the most illustrious names in racing.