Club Racing: A closer look at Spec Miata shocks

Images by Penske Racing Shocks

Club Racing: A closer look at Spec Miata shocks

SCCA / SportsCar Magazine

Club Racing: A closer look at Spec Miata shocks


SCCA racers know Penske is the new shock supplier for Spec Miata, but what’s the story behind that story?

In 2018, the team at Mazda Motorsports set out to correct a long-brewing issue with its Spec Miata damper package: guaranteed compliance. As Joshua Smith, Specialist Technical Development at Mazda Motorsports, explains, “There really wasn’t a solid specification for the Bilstein shocks, so the start of the process to fix the problem involved identifying the inability to thoroughly tech the Bilstein shock, and then figuring out how to solve the problem.”

The challenge came, in part, due to the nature of the original shock. As a mass-produced damper intended for street use, there was a fairly wide performance envelope of the Bilstein shocks, and that made it difficult for Mazda Motorsports to develop a specification to hold Spec Miata shocks to. Beyond that, several creative racers discovered they could re-valve existing Bilsteins in order to meet the letter of the rules, even though this was outside the intent of the class.

Image by Mark Weber

That brings us to another significant issue: People were able to modify the Bilstein shocks without significant indication they had been modified. “We originally didn’t start out with the idea of replacing the Bilstein shock,” says Smith, “it was more like, ‘How do we tech a spec-series shock?’ That led us to try a couple of things that inevitably did not work, and then it morphed into figuring out how to create a shock that would do what we wanted.”

Around the same time, Bilstein began retooling one of its production plants, and that led to a global shortage of many different damper applications – including Spec Miata shocks. “There was almost a year of shortage,” Smith recalls.

The lack of a solid tech process – and damper inventory – began to force Mazda’s hand. “We went to an RFP [Request For Proposal] process with nine shock manufacturers to compete for what we set as a criterion for the Spec Miata shock package,” says Smith. “The shocks had to be a direct replacement in order to reduce cost; we didn’t want people to have to buy components that weren’t needed. We also wanted the shocks to be crimped sealed, with spec compression and rebound forces.”

Ultimately, Mazda Motorsports saw this as an opportunity to reset and fix a number of issues with the old suspension package. “It really wasn’t built for what we were requiring of it,” Smith says of the original Bilstein shock package. “We took a street shock with very low forces, putting more spring on it than it was engineered for, and expected it to perform. We really wanted to tailor a shock to the class – not only the springs, but the swaybars and the weights of the vehicles.”

As the RFP reached Penske Racing Shocks, there was an immediate interest from the development team. “A guy who works here has a Spec Miata and he was monitoring the shock situation, so we were waiting to hear if there was anything we could do,” says Aaron Lambert, Director of Operations at Penske Racing Shocks. “Then Josh and David [Cook] reached out to us and said they were going to open up the Spec Miata shocks for a quote. They gave us and all of the other manufacturers a target.”

For Penske, this process was nothing new, they were already the spec shock for Spec Racer Ford, along with decades of experience as a supplier for NASCAR, IMSA, and they had a wide range of applications. “We were confident going in,” says Lambert. “We have a lot of customers, not in Spec Miata, but other types of racing that compete in Miatas. So, we have a good background and had a pretty good feeling that we had a setup that would work really well.”

With shocks in hand, the team from Mazda Motorsports, as well as representatives from the various shock manufacturers, completed an extensive round of testing to narrow the field. “It was a four-day process of eliminating various setups,” says Smith. “Penske just continued to shine through the whole testing procedure. It really was the customer service and personnel behind Penske – they wanted to do what was best for the community.”

During the initial round of testing with Mazda Motorsports, the team at Penske found they were close to where they needed to be. “We went down to Carolina Motorsports Park for that test and, performance wise, we did very well,” says Lambert. “After the first test at CMP, we kind of understood what the baseline setup was and how customers were setting up these cars.

“A lot of it was initially driven based off of the bump stop, and how they were using the Bilsteins. Once we got though the test and had a chance to talk to Mazda and SCCA, we were able to find out what they were trying to go for, and a lot of it was, ‘Let’s get off these bump stops.’ So, after that first test, we decided we could valve the shocks a little differently. Then we went to our shaker jig and tested.”

A second round of testing took place at VIRginia International Raceway, with this round focusing on whether the shocks could meet Mazda’s goals. “Mazda said they had to look after all of their customers, not just the top performing guys, and not just the entry level – we have to cover everybody,” says Lambert. At that test, Lambert notes that their setup was on target. “We were really happy at the second test at VIR,” he says. “Not only was the performance better, but the car was easier to drive.”

While improving the driving experience was important, so was maintaining the balance among the various chassis in Spec Miata, and providing a good value. “It had to elevate all three cars equally – we wanted to maintain that balance of performance while elevating all of the platforms,” says Smith. “Even though we doubled the price of the old shock, the value that it brought because it can be rebuilt, really spoke to the longevity of the class.”

Being chosen as the new Spec Miata shock, Penske was facing fulfilling a large order in a very short time – but that didn’t mean Penske was going to change its manufacturing process. “It’s a big project and we are excited to work with Mazda Motorsports on it; but at the same time, it’s still our race shop that is going out there,” says Lambert. “We didn’t go to a production line or robot assembly or anything like that. Every single shock that is going on these Spec Miatas is hand built by the same technicians that are going to our sports car races, IMSA races, IndyCar races; they are the same guys. Every single shock is dyno tested just like all of our other race shocks. I think that is where the end user in Spec Miata is really seeing the difference between what a properly built race shock is compared to an assembly line or mass production shock.”

Racer feedback on the updated Spec Miata shock package has been favorable as well, and the adoption rate among SCCA racers has exceeded everyone’s expectations. “We underestimated how quickly everybody would jump to them,” Smith admits. “To date, we have sold 692 sets of Penske shocks. We keep ordering more to keep up with demand and we’ve not really seen a decline in orders. I expect to see another wave once racing picks up in the Northern parts of the country.”


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