Moving from the world of muscle cars into the world of road racers is a shock for many. Not only is the culture more competitive by nature, but there are fewer road racing folks are interested in paint and trim. Instead, they’re intent on finding the ideal setup and shaving tenths off their lap time. This detail-oriented culture can be a little fussy at times, but it’s a great environment for learning how to make the most of the machinery. Therefore, lots of back-and-forth ensues regarding the right spring selection, the right amount of swaybar and how to balance front and rear stiffness to help – and, truthfully, it never ends.
Now, most cars made into Pro Tourers are front-heavy. There are plenty of advantages to having a big lump slung over the front axle, but a weight distribution conducive to corner carving isn’t necessarily one of them. Therefore, it’s important a driver learns that the front axle needs the right amount of tire and spring/roll stiffness to support the amount of weight sitting over it.
It’s a wise approach to ensure the front tires are wider than those of a typical staggered street/drag setup. Often times, some run a square setup – meaning equal tire widths front and rear – to create a more neutral setup that can understeer as easily as it can oversteer. As long as the car isn’t too nervous at the rear, this setup usually yields the fastest cornering around a road course or an autocross track – at least for those getting started with serious corner carving.
To keep the fronts working well, it’s critical to get the right sort of springs for the amount of weight over the front axle. Say a supercharger is added to the mix. Not only must the weight of the motor be taken into consideration, but the blower and all its ancillaries must be supported by the right spring. Therefore, off-the-shelf shocks might not do the machine justice – it really depends on the specific circumstances, and finding the exact corner weights is very useful.
Similarly, the rear needs to be compliant and adequately stiff for the circumstances. Too much rear swaybar will lead to spiky breakaway and nervous cornering, and depending on the power levels, it’s helpful to keep the rear bar moderately soft and, if traction is an issue, it may even help to disconnect the bar entirely. As always, the goal here is to make the car somewhat forgiving and encouraging.
Finding enough traction isn’t easy, but while a little compliance is helpful, having enough rigidity to keep the rear suspension from flexing unnecessarily during the cornering phase is also important. For those who don’t want to retrofit the rear entirely, a panhard bar can limit unneeded movement and keep the rear predictable.
It’s equally important to balance the front and rear levels of grip so they complement one another. Both axles must work in unison for the driver to feel confident in their car. Forget rake and squat, and try to make the rear axle respond similarly to the front and, for starters, try to get a car that will break away in equal amounts front and rear.
Muscle car aficionados will realize they need some surprisingly stiff springs if they want their muscle car to rotate. This might sour the cruising capabilities, but there’s often a tradeoff in this department between agility and comfort – unless some modern and very pricey pieces are implemented.
That said, it doesn’t take big bucks or top-shelf parts to excel with a Pro Touring build either, but it does take the pieces aligning well and working together. Once a set of decent parts has been decided on and installed, it’s incredibly important to get a good alignment so that the parts’ potential is met. Avoid going to the basic service centers and try to find a shop with some road racing expertise – they’ll have a better sense of what caster and camber settings will make a Pro Tourer turn.
“Bolting on parts isn’t finishing the job,” warns V8 Speed & Resto Shop’s Kevin Oeste. “Find someone you can work with on a suspension setup – maybe consult the local BMW club for help.” In other words, be prepared to do some fine-tuning – parts alone won’t make much difference.
There are three items which ought to be given some serious thought: shocks, which should be given precedence; an upgraded swaybar, usually at the front axle; and modern bushings, to take play out of the suspension. Shocks from companies like Bilstein can be had for a reasonable amount. A thicker front swaybar is important for steering response and front grip, but must not be overdone.
Though they’re not given much credit, bushings are incredibly important in reducing the amount of slack in a suspension setup. Consider replacing the bushings with modern delrin pieces—they can often retrofit the older ones and make a factory control arm quite effective for little money. These small modifications, in aggregate, can make a massive difference in the way a car responds and transmits information through the steering and chassis.
Other overlooked areas include things like steering hoses and steering fluid. “Don’t forget the basics,” mentions Oeste. If these parts are outdated, some freshening up is a quick and simple way to putting a driver in better communication with the front axle. Once the driver is comfortable with the inputs and the behavior of the vehicle they can push the limits of adhesion, improve their car control and whittle down their lap times.