Along with a clean-sheet approach to its look, the introduction of the sixth-generation Mustang in 2015 brought with it several pivotal changes to the iconic pony car. Improving the Mustang’s handling prowess was high on Ford’s priority list, and getting there required the company to finally make the switch from the old-school solid rear axle, to a fully independent rear suspension.
This 2015 Mustang EcoBoost’s suspension was tuned for performance from the factory, but ride quality was still one of Ford’s primary goals when selecting shocks, springs, bushings and other suspension components. Acceptable levels of noise, harshness and vibration can be a fairly subjective matter, so OEMs tend to err on the side of caution. In the interest of safety, nearly all factory suspension systems are also designed to understeer at the limit, which can mean a floaty, disconnected feel from behind the wheel.
To put it another way, the suspension lacks a feel of performance because Ford wants to keep the car comfortable and safe for non-enthusiasts. Which, if we’re honest, likely makes up the majority of buyers who aren’t opting for the GT350 or GT350R. That means that the springs and dampers are pretty soft to soak up the bumps and undulations in the road, and the sway bars are tuned for understeer if you come into a corner too hot.
That may be fine for the lion’s share of Mustang owners, but what if you’re looking for some serious cornering capability? That’s where the folks from Maximum Motorsports come in with their Starter Box kit for the 2015-and-up Mustang (PN SBX6-61).
What You Get
2015+ Mustang Start Box Suspension Package From Maximum Motorsports
- Fits all 2015 Mustang models (excluding GT350/GT350R)
- Includes KONI single-adjustable front struts and rear shocks
- Choice of Eibach Pro Kit or Sportline lowering springs
- Caster Camber plates
- Eibach adjustable front and rear Sway Bars
- PN SBX6-61
“Ford’s primary goal is to minimize noise, harshness and vibration,” Chuck Schwynoch of Maximum Motorsports told us. “They don’t want your grandma to complain about ride quality. This in turn limits the car’s handling prowess for a driver who wants cornering ability, quick steering response, and minimal body roll and brake dive.”
Using a 2015 Ford Mustang EcoBoost as our test bed, we’ve bolted up Maximum Motorsports’ Starter Box kit to find out if we can transform this pony into a thoroughbred performer on the street.
Available for the Mustang V6, EcoBoost, and GT models, the Starter Box includes KONI single-adjustable struts and shocks, Maximum Motorsports’ Caster Camber Plates, an Eibach sway bar set, and a choice of different springs (which you can find here).
All told, there’s enough hardware to comprehensively transform the handling capability of a car while also dropping the stance a bit as well. This gives it a more aggressive look and lowers the vehicle’s center of gravity as well.
“The stock suspension tends to have relatively soft spring rates to make for good ride quality,” Schwynoch explained.
“In turn, the dampers are tuned to match the soft springs. For example, a stock 2015 Mustang GT is very softly sprung and softly damped in the front. That under-damped front makes the car feel floaty and disconnected from the road. On track at 100 MPH, the car feels under-damped and exhibits a very uncomfortable amount of body roll. If a driver swaps out the stock tires for ones with more grip, they’ll notice that they need to back off the throttle because the limit to going faster is the handling itself, rather than a lack of tire grip.”
Although the Maximum Motorsports Starter Kit is designed to substantially improve the handling capability of an S550 Mustang, it’s tuned to be street friendly as well. That means that while the performance of the suspension is increased dramatically, it doesn’t come at a significant cost in terms of ride quality.
The trick is to find the acceptable compromise between a desired level of handling and acceptable ride quality. – Chuck Schwynoch, Maximum Motorsports
Testing is often done “blind”, meaning that the drivers do not know which setup they’re testing, and are conducted over varied surfaces that include rough streets, railroad track crossings, good and bad two-lane roads, and well maintained freeways.
“After all of our drivers drove a particular setup; they met and discussed each setup, and reached a consensus about how we would describe each setup to customers, as far as ride quality and handling goes,” he said.
“Our goal is to guide customers to the setup they’ll be most happy with. When talking to customers we question them to get a sense of their goals, and how important ride quality is versus handling. This points them to the best springs. In any case, the Koni dampers have enough range of adjustment that they work well with any of the spring sets we offer for the S550 Mustang.
“The trick is to find the acceptable compromise between a desired level of handling and acceptable ride quality,” Schwynoch said. “Ride height has a significant effect on ride quality, as being too low for a particular spring’s rate will cause the car to hit the bumpstops frequently.”
Since the Starter Kit provides so many integral components of the suspension setup equation, there’s a bit of elbow grease involved to swap it all out. Fortunately, it’s essentially a plug-and-play type of operation. We began with the front-end of the Mustang.
Removal of the front strut from the strut plate required either a half-inch impact gun or breaker bar, and we also grabbed a spring compressor to do this job. If you’re not comfortable working with a spring compressor, we’d highly recommend letting a shop tackle this one, as those springs are under some serious pressure.
Since we opted to include the optional Eibach sway bars with our kit, we removed the stock front sway bar at this point as well. This is a pretty straight-forward process. Start by unbolting the bushing clamps on both sides of the sway bar, then unbolt the sway bar from the vehicle by removing the end link bolts on each end.
Since lowering the car changes the suspension’s geometry, it’s important to correct the vehicle’s alignment in turn, and caster/camber plates help to do just that. “Lowering the vehicle beyond the factory settings changes the alignment specs,” Schwynoch explained. “And adjustable caster/camber plates allow you to bring it back into spec.”
Maximum Motorsports’ design also improves upon the stock configuration by preventing the strut shaft from moving out of spec during operation. It does this using a PTFE-lined spherical bearing, which eliminates the unwanted deflection allowed by the rubber used in the stock upper strut mount. They also allow you to increase negative camber for competition, and their design provides better steering response as well.
Installation of the plates is simply a matter of swapping out the factory rubber mount for the MM pieces. After installing the new shocks, struts, and sway bars at both ends of the car, it was time to hit the pavement to see how it all came together out on the road.
Before the upgrades, this car wasn’t exactly inspiring confidence in its driver. “The easiest way to put it was that it was very sloppy,” said Danny Campagna, owner of the Mustang EcoBoost in question.
“There was no feeling or pushback – just sort of numb, and I think the reason for this is partially because of the tires and also because of how the dampers are tuned from the factory. While the car was equipped with the optional Performance Pack (which includes heavy-duty front springs, unique chassis tuning, and a larger rear sway bar), there was still a lot left on the table in terms of performance.” Post-installation, Danny is singing a slightly different tune.
“As soon as I got in the car and took the first turn with the new suspension package, I immediately felt less body roll,” he said.
“Without even experimenting with the settings for the adjustable Koni front and rear dampers, the new Eibach Pro Kit lowering springs (combined with the larger adjustable front and rear sway bars) make for a lethal street/track handling set-up. With the new suspension installed, every corner is a new opportunity to keep pushing the car even on the stock tires.”
“Mid-corner, I can feel the car giving a more prominent amount of feedback, Danny continued. “What was once a dead zone is now communicative through the corner. Everything tightens up as if the car is bracing itself to rocket out of the corner without any hesitance, and it’s a feeling that is confidence-inspiring.”
That sounds like a pretty solid endorsement to us. If your pony could use a suspension makeover, the Starter Box kit from Maximum Motorsports is undoubtedly a great option if you want to do the job right the first time the car goes up on the lift.