Weight is the enemy of performance. It holds a car back, causes slower acceleration, slower response times, and as such, slower performance. As enthusiasts, we often think of weight reduction in terms of major components. Engine components, lightweight body panels, lighter seats, and seat deletes. How often do we really think of weight reduction in our wheels? Especially in a car that isn’t going down the dragstrip, but instead is heading around corners and cones at an autocross event?

For Project 5-liter Eater, our 2015 Mustang EcoBoost, weight savings has been a ticket to V8-level performance with half the cylinders. Tipping the scales several hundred pounds under its V8 brethren, our EcoBoost Mustang already had better weight balance than V8, and even V6-equipped Mustangs.

We chose Forgeline's Transparent Smoked Gold finish for our one-piece monoblock wheels. These wheels, even in 18x10.5 inches, weigh in at just 19 pounds one ounce, compared to 32 pounds for our stock parts.

To improve grip on the autocross we went with Bridgestone’s RE71-R tires, in 275/40R18. These tires are 200 treadwear making them legal for competition in SCCA’s CAM-C class, and the R compound technology is the latest in sticky grip for autocross autocross.

To further reduce weight and gain more cornering performance safely, we turned to Forgeline for our next competition modification. The company outfitted us with a set of its GA1R wheels in 18×10.5-inches at all four corners. While we could have selected a larger wheel package, going with an 18-inch diameter opens up our wheel options while keeping weight to a minimum.

We’ve discussed Forgeline’s manufacturing processes and quality standards at length in previous tech articles. Rather than talk about the monoblock construction or extreme light weight of our GA1R wheels versus the heavy weight of the OEM cast wheel, we think it would be prudent to take a look at competing on a lighter set of well-engineered wheels and why that is important.

Bred For Racing

It doesn’t hurt that, even though it’s all business in the performance department, the GA1R wheel offers outstanding looks; especially in Transparent Smoked Gold against our Race Red paint.

Forgeline doesn’t simply build good looking wheels from huge billets of aluminum at its Dayton, Ohio facility. The company engineers its wheels to safely win races. The fact that any of the company’s wheel designs can withstand the rigors of competition speaks volume. Forgeline won’t manufacture a wheel that sacrifices function in the name of form. Meaning that while all of its designs are good looking, those designs must also meet the company’s stringent safety standards. “Forgeline refuses to build a wheel that compromises strength and weight,” said Steve Schardt of Forgeline.

Dealin’ With Deflection

Gold Service

Forgeline offers its customers full-service mounting and balancing of wheels and tires before delivery. This ensures that the tires are properly mounted and balanced on the wheels. It also prevents damage to the wheels by an inexperienced technician at your local tire store.

Deflection is the amount a wheel bends under a cornering load. There are a number of factors that influence how much a wheel deflects. While we like to call our EcoBoost Mustang “light” the car is actually very heavy, at over 3,600 pounds with the driver, and occasionally carrying a passenger around the autocross cones. For all intents and purposes, this is no lean car.

When you take that weight, and you add the latest in tire technology, the forces exerted on a wheel in competition increase dramatically. According to Schardt, the coefficient of friction (CF) has changed for 200 treadwear ‘street’ tires over the years as well, as tire technology improvements have also increased grip. This means that Forgeline has had to keep up by offering a competition wheel with a 2,100-pound load rating.

If you add a set of racing slicks for competition use, the CF goes up to a factor of two, which means the wheel’s load capability drops by half due to the increased grip. This expands the need for a sturdy wheel when used in competition, according to Schardt.

Schardt said that Forgeline pays specific attention to the grain flow of its forgings, as well as the design. “Design is what makes a Forgeline wheel. The grain flow of the forging plays a big part in strength, as it adds to the sturdiness of the wheel.”

“With a heavy car like the Mustang and sticky tires, going around a road course and experiencing hard cornering loads, you’re going to need a wheel that can withstand those kinds of loads,” said Kenny Brown, a longtime Mustang racing guru and suspension engineer.

“The Forgeline wheel will do that. There are a lot of cheap wheels on the internet, and those are fine for driving around town and looking cool, but I wouldn’t put those on my customer’s cars for racing.” Brown’s relationship with Forgeline goes back to the early ’90s.

Forgeline installed its metal valve stems before mounting our tires. The attention to detail on these wheels is the same quality as a set of street wheels.

Longtime Forgeline dealer, Mustang builder, and championship-winning road racer Paul Faessler concurred with Schardt and Brown’s sentiments. “The strength and the stiffness of these wheels help the tires work better. You’re not getting flex and deflection. Anything you can do to reduce that in the suspension is helpful for handling.”

Faessler hits on another key point in that statement. As the suspension reacts to changes in track conditions, bumps, cornering loads, wheel-to-wheel racing, and even contact with other cars, wheel deflection plays a critical role. Essentially, if the wheel acts in a more predictable manner, tire contact patch and suspension setup becomes more predictable, and the data from the car is more reliable.

“When turning a corner, you’re looking for less deflection, and you don’t want the wheel to move at all. If the wheel moves, your contact patch changes and then your suspension setup is inconsistent. The less deflection, the better; because it takes the wheel component out of the picture,” Schardt told us.

Reducing Weight One Corner At A Time

The difference in performance is noticeable both in acceleration and when carving corners in competition.

We mentioned our GA1R wheels weigh in at just 19 pounds one ounce, making for a 13-pound weight reduction (per wheel) from the wheels we ran in our previous racing season. Traditionally, Mustang and musclecar enthusiasts think of weight reduction at the wheels in terms of acceleration, and rotating mass. This is beneficial because the lighter the wheel and the less rotating mass, the faster the car can accelerate, and the faster it will react from the moment of inertia (MOI) to accelerate. There’s more at play here though, when you’re looking at a wheel from the standpoint of how a car handles.

“Removing weight at the wheel reduces unsprung mass, which translates to how quickly and more accurately the suspension can react to changes,” Brown said. “For example, if there’s a large seam or bump in a corner, or simply the flow of the racing surface, because there’s less weight at the end of the axle or spindle, the suspension has less work to do to compensate for these changes and keep the car moving in a predictable manner.”

A side-by-side comparison of a street wheel and tire (left) and our Forgeline competition wheel and Bridgestone tire (right). The difference in weight is 13 pounds, equating to a total of 52 pounds in reduced weight.

While we all want to accelerate faster and get through a corner or a lap quicker, there’s something else to consider here as Faessler pointed out. “The lighter rotating weight helps you under braking because you’re not slowing down a heavy wheel,” he said.

Braking performance plays a critical role in the world of auto racing, whether you’re going 45 to 60 mph around an autocross course, 150-plus in a World Challenge car, or nearly 200 down the straight stretch in a NARRA GT-U Mustang; the ability to slow the car is nearly as important as the ability to accelerate it. Less time on the brakes means more time on the throttle, and as Faessler pointed out in his previous statement, that lighter rotating mass will help a driver slow the car significantly faster.

Implementing A Safety Net

So why not run a cast wheel? There are hundreds of cast wheel designs on the market for our Mustang. Some options available are even significantly lighter-weight than the OEM wheels we ran last season, and have an extremely high load rating.

Admittedly, those wheels look great on a street car; but for our street use, we’ll continue to use our OEM cast wheels. However, for the autocross or road course, there are some other reasons to go with Forgeline.

The less deflection, the better; because it takes the wheel component out of the picture. Steve Schardt, Forgeline

“Safety is a key factor to consider. These wheels are designed to race, and there’s a three year structural warranty against failures. The fail mode for a forging is a leak. The fail mode of a casting is catastrophic,” Schardt explained. What Schardt is referring to is that if a structural failure occurs in a forged wheel, the way that wheel fails will typically result in an air leak. And on the race track this leads to a flat tire, which in turn sends a car to the pits for a tire change.

In a cast wheel, structural failures due to stress are often catastrophic. At high speed, this can cause the wheel to shatter or even break into multiple fragments. This type of failure carries much more severe consequences under high speed cornering. There’s also contact to consider, as Schardt pointed out. “With wheel-to-wheel contact in racing, if two cars are side-by-side and there’s contact (and one car is running a cast wheel, the other a forging), when that contact occurs and those wheels collide, the forged wheel is going to win.”

Faessler commented on his experience with the three-piece designed wheels as well. He said, “The strength, the weight, and the ability to repair, means style for customers who want something different for the street. We’ve run our cars very hard, we’ve been knocked around, dinged wheels, bent the outer shells, and we’ve never had any problems at all.”

“I prefer the one piece because they’re so much stronger,” Brown said. “A one piece wheel will take much more of an impact. We’ve never hurt a one piece Forgeline wheel ever.”

Service After The Sale

For professional races, Forgeline is there on race day to support race teams that have made its name so prominent in the world of auto racing. Race day reputation extends to its dealers and customers alike.

“They’ve been a very high quality company, and they’ve always been great to deal with,” Faessler said. “It’s a consistent product, and the quality has remained consistent over the years. The wheels are very rigidly tested, and we feel the entire wheel package is a step above.”

At many racing events like the World Challenge, Forgeline has representatives on-hand to assist racers running its products. On-site support and repairs are often available at these events, and Forgeline often goes above and beyond for the teams it supports to help them get to the finish line.

Our Car On The Autocross.

Everyone we interviewed for this article told us we would notice a difference in Project 5-liter Eater the moment we hit the autocross with our car. We’ve had plenty of drag racing experience with lighter wheels, and a lot of autocross seat time in our car during this past year with OEM cast wheels, and we knew there’d be less weight, but how much of a difference would that weight translate to on race day?

Brown echoed our experience over the years, and said, “I can feel a huge difference in the steering and how the suspension is reacting when you switch to a Forgeline wheel. The quicker the suspension reacts, the better the car works.” Still, this author was left wondering just how much of a difference there would be.

At the Kentucky Region SCCA’s season opening test-n-tune, we had a chance to find out. The course was full of marbles, and our tires admittedly needed additional heat cycles. Still, we found out just what a difference a set of wheels can make.

At launch, the car’s acceleration was instantly recognizable as improved. We actually had to do some throttle modulation to keep tire spin down, and keep the car inline for the first slalom right out of the gate. Around corners, it was nothing short of astonishing how much better the car worked. There is a definite improvement in how the quickly the car could turn, and how fast our inputs with steering, throttle, and braking were translated into action by the car. There was a definite learning curve for mentally adjusting to this newfound responsiveness.

After three events behind the wheel, we can honestly say we’re impressed. Our investment into a set of Forgeline wheels for the car, and a set of high-quality tires meant for competition has to rank as one of the top modifications we could perform to make our Mustang EcoBoost project car more competitive. Not only does the car feel and perform much better on the autocross, but if and when we hit the road course, we’ll have greater peace of mind knowing that our wheels are safer and will stand up to the rigors of our next road course adventure throws at them.