Thankfully the Boss 302 proved the first Mustang to get the coveted treatment. The selected tires were the Pirelli PZero's in 255/40R-19 front and 285/35R-19 in back. The Laguna Seca edition got the same tire, but in an even stickier R-compound.
"Having decided to use an off-the-shelf tire [that worked and saved development time], we started to develop the chassis around that. ...Being able to walk from the '10 to the '11 [Mustangs] we could go further and we knew that, and the staggered tires opened that up in terms of chassis development."
Quiet, focused, and with a self-described butt “that’s shaped like a Mustang seat,” Steve
With the tires set, the "big adjustment knobs"--springs, sway bars and dampers--are the next items to tune. "We started to work on the springs, and then all kinds of internal hurdles, like we were already maxed out on rear spring rate. So we had to do some things, like limiting rear rebound travel to keep the springs in the pockets and things of that nature. To go above where we were with the Track Pak and Brake Pak, we had to limit the travel on the rebound side for the damper. ...Luckily we had support from management because each [challenge] represents its own compromise ...but we did manage to push through all that."
"So, get the tires. Work on the springs. Work on the bars to get the balance in the car. Always our goal was to make the car driveable and fast. And approachable. You can jump in these cars and drive them hard... Early on we decided that the [BMW] M3 was our target and with the M3, you have to wring its neck to get anywhere near our lap times. With the Boss, to me, it comes easily."
"There are also more subtle things in there--all the bushing work; we even did top mounts [for the front struts]. We never did mention that to anybody. We did top mounts in the front, which was a pretty cool improvement in its own right." The top mounts are 50-percent stiffer radially.
In the end, the Boss 302 and Laguna Seca received the following suspension hardware:
Spring rates are in Newtons per millimeter; sway-bar diameters are in millimeters. Front lower control arm bushings are common in all Mustangs; the Mustang GT uses a softer rear lower control arm bushing than all others.
When Ford says the Boss 302 is a race engine, it isn’t kidding. You’re looking at the only
Generally things get stiffer as expected when moving from a Mustang GT to the track-happy Laguna Seca, except for the lower front spring rates on the Laguna Seca. Kevin explains, noting "The Laguna tune is all about handling the massive rear tire, also, because it has a more aggressive [tire] compound, the Laguna has a little more understeer margin. That's because the tires come up to little bit different temps and you have to manage it a little bit better. If you were to make the Laguna as balanced as the base car, there'd potentially be times where novices would be in trouble. We don't want to do that, so we got a little bit more (understeer) margin in that car."
With the suspension basics set, the tuning moved on to the dampers [shocks], and finally the electric power-assisted steering, or EPAS. The shocks are five-way adjustable units sourced from Tokico, but with Boss-specific valving. The EPAS is a whole new engineer's playground full of twiddle knobs to be adjusted. After decades of a few coarse adjustments to hydraulic power steering, EPAS opens many new tuning doors.