Here in America, where we have long straight roads crossing most of the country, automotive development traditionally lie in producing huge engines that were best suited in pulling a car down a quarter mile. Just look at some of the classic muscle cars that were produced: the 454 Chevelle, 455 Firebird, 440 Charger; all legendary cars, but none of these could make it around a bend without drama.
In recent years, there has been a lot more attention the making cars handle well. The C6 Corvette for example is a very good handling car. I even hear that there are factory suspension options on the new Mustang which make that car handle very well. But for the most part, if you car isn’t as sporty as those two examples, it probably handles like a brick.
Its not like the factories don’t know how to make a car handle properly. All of the major car companies at one point in time were involved with racing and know how to get things done. The problem is (maybe due to our endless straight roads?) that the general populace doesn’t know how to drive a car that has a little oversteer in the suspension. With this said, it makes it seems impressive that GM chose to set up their corvette this way knowing that the average age of the people who drive that car is around 50 – a group I don’t usually associate with high performance driving.
The danger of having oversteer happens in a situation such as this: Your grandmother is driving down the highway at 75 mph and lifts off the throttle while trying to avoid something on the road. Lifting off the throttle and turning sharply at the same time causing the rear of the car to become loose sending her spinning into a bus full of children. And of course, because we live in a litigious society, grandma and the families of all the children are now suing the car company because her car had an “unintended acceleration” or some other buzz word to hide her poor driving.
This story may sound like a joke, but things like this really do happen. I was having a discussion with my father about this and he told me that the mother in-law of a friend of his died in a very similar situation. You can see why its a safer bet for the auto companies to make a car that just understeers off the road.
Manufactures of main stream cars (sports cars included) generally set up the cars so that they have understeer built in. It doesn’t matter what the car is or its weight bias. The factories simply set up the cars so they don’t oversteer.
So what does the factory do to limit oversteer?
Spring rates (and anti-roll bars) are probably the biggest factor. By keeping the spring rates at one end the car below a certain percentage of the opposite end, this will generally cause the relatively stiffer end (usually the front) to overload the tires and induce a ‘push’ in the car.
Another trick is to limit camber. If you walk around many sports cars like my old RX-7 or my current 350z, you will notice that the front wheels have less camber than the rears. This causes an inefficient use of the front tires so they simply have less traction.
Toe angles are also set to prevent oversteer. This is particularly done on the rear suspension where having a degree or so of toe-in increases stability.
Putting larger tires on the rear of the car will also limit oversteer because of the increased traction at that end. A staggered setup with big tires on the rear might look cool, but for most cars it just induced bad handling.
How can I move the handling balance of my car so its more neutral?
Well, you have probably figured out that if the factory does the above to make you car understeer, than you can do the opposite to loosen it up. Luckily, you shouldn’t have to tune your car yourself since there’s a lot of companies out there that have done all the hard work and offer packages that you simply have to install. Putting in aftermarket sway bars (anti-roll bars) is probably the easiest way to change the handling balance of your car. The factory usually puts in a very soft rear bar and replacing that with a stiffer one can really wake up your cars handling. A lot of these sway bar kits are also adjustable, allowing you to find a setting your comfortable with. Installing aftermarket sport oriented springs from companies like Eibach and H&R will also change your handling balance for the better.
Another option is a full coil-over kit which include springs with matched adjustable dampers. These kits also generally come with an upper mount for vehicles that use struts which will have adjustments for camber and possibly caster. The down side to a full coil-over system is that they are very expensive. There is some cheap lower quality ones out there, but I would stay away from those.
This pretty much covers a lot of the big things, there’s still a few others like installing stiffer bushing to prevent suspension deflection; but doing that can be quite laborious with little return. It should also be noted that by adding things such as stiffer springs and roll bars, ride quality is going to suffer. Make sure your goals are something you can live with, especially if your car is a daily driver.