Q: “I’ve been told to work on my driving before making mods and tuning my car, and I’ve taken that advice. But my car understeers badly. No matter what I do, I just can’t seem to get it to turn. Can you tell me what I can do with my driving to help this? And then, what should I do to my car to make it understeer less?”
A: I’m going to turn your questions around and answer them in the opposite order – what to do with your car first, and then what to do with your driving.
As I wrote about in my How to Tune Your Car’s Handling eBook (free to download at https://speedsecrets.com/tune-car-handling/), start tuning your car by using the tools you have. So, if the only tool you have is a tire pressure gauge, then adjust tire pressures; if you have camber gauges and can adjust camber angles, do that; if you have aero devices on your car (splitter, rear wing), then use them.
Understeer is simply that the front tires have less grip than the rear tires, so your goal is to give them more traction. In terms of tuning your car, start with softening the front roll stiffness. You can do that by changing the front springs to softer ones, softening the front anti-roll bar, or reducing compression and/or rebound on the front shocks. You could also lower the front ride height. Oh, and back to the tire pressure gauge… either reduce tire pressures, or increase them. Yup, there’s no way of knowing for sure which way to go without trying and testing different pressures. If your tires are already slightly over-pressured, then lowering them will help; if they’re under-pressured, then increasing the pressures will help. Make some reasonably big changes – at least 4 psi – in both directions to get a “read” on which direction you want to go before fine-tuning with smaller adjustments.
As for your driving, you can manage understeer by either loading the front tires more, or less. So, you could trail brake further into the corners to keep load on the front tires. However, the understeer could be caused by overloading the front tires, so you could release the brakes earlier to reduce understeer. There’s only way to find out which one works, and that’s to try them both. However, if I had to start with just one option, I’d trail brake more to load the fronts more, as that will work more often than the opposite approach.
You could also drive the line through corners that allow you to begin to unwind (straighten) the steering wheel sooner, to reduce the amount of time you spend turning the steering wheel. I’d also try being a bit more gentle with the initial turn of the steering wheel entering corners, so it gives the front tires more time to change direction of the car.
Well, it depends whether you have a stock passenger car with stock springs or a race car with modified suspension. The difference is that a stock car typically has softer front suspension for the purpose of causing understeer because manufacturers believe that it is better to plow off the road than to slide the rear end and catch the slide or at least hit whatever you are going to hit with the back end (unless you drive a Porsche:()
In the case of a stock passenger car, you may need to increase the front roll couple by first increasing the spring rates and then and only then increasing the bar rate by a SMALL amount. If you have access to an adjustable bar install it (hook it up with both wheels on the ground to ensure there is no pre-load in the bar.
But first, check that everything with the suspension is tight and aligned properly. I used to work (a long time ago) for a shop that did suspension upgrades to Pony cars and Corvettes. Understeer was the major complaint we heard from customers. We always checked the ball joints, tie rod ends, and in those days the pitman arm bushings for wear. We would not align a front end or install race parts if any of those parts were worn out. The major modification we did was to change the “tree trunk” size sway-bars some of the customers had installed, which made the push worse.
The first change we would recommend was with the tires, then good high performance adjustable shocks, stiffer front springs Starting with twice the rating and we had to cut them to lower the car and equalize the ride height.
Then we installed control arm bushings that we made out of aluminum. Those are available in Delrin now.
If you have a leaf spring rear suspension do not repeat do not install a track bar (Panhard bar). Doing this would induce a second roll moment and simply lock up the rear suspension.
Remember to realign the front end as the last thing you do and set the toe very last.
PS: A “push” may be as simple to fix as laying off the brakes some at corner entry.
If you need more info look me up on my website APPLIEDSPEED.COM
With a full-on tace car, the front end may be too stiff causing the front tires to underload by transferring the weight to the outside rear tire. Here a real tire pyrometer may tell the story. By real I mean a pyrometer with a needle, so you can test the temperature inside the rubber, not the surface temperature.
If you have to raise or lower the front of the car you probably do not have the right springs, bars, and shocks on the car. The shocks are used to set the handling going in and out of turns and for braking and accelerating. Again if you need more help check me out at APPLIEDSPEED.com