Next weekend I will travel once again to VIR and spend Saturday and Sunday doing laps. This time it will be the north course. It is over two miles long and provides a nice version of this great track. The weather looks like it will cooperate and the grass should be green.
Over the past couple of weeks we have been busy at Performance Chassis with many people getting their cars ready for this event as well as the autocross season. That means new tires and alignments. It is nice to start off the season with some fresh rubber and many of the autocross crowd run race tires so that they get maximum adhesion. Another key to getting maximum grip is to have a “spec” alignment done. This kind of alignment can be quite different from what the factory recommends. Most vehicles coming from the “factory” are set up so that as the car approaches the limits it will do so in an understeer mode where the front tires push their way through a turn instead of cornering. This is done because it is not as disconcerting for a driver as having the tail of the car get loose and come around or oversteer. The theory is that understeer can be recognized more quickly and the driver can correct simply by slowing down. Understeer also severely limits the speed you can carry through a corner.
To counteract the predilection of understeer we will often add negative camber to the front suspension as well as maximize the caster. Negative camber places the bottom of the tire farther out than the top of the tire. This is a lot like placing your legs apart so that a push on your shoulder won’t send you toppling over. Caster can help by adding more negative camber to the outside tire when the wheel is turned. Castor also helps the wheel to come back to center as you come out of a turn.
Not all cars will have adjustments that allow for these kinds of changes. Miatas and Honda S2000 cars do have factory adjustment points that allow you to make those changes. Other cars will require aftermarket devices like camber plates at the top of the struts to give you that kind of adjustability. Cars with solid rear axles, like the Ford Mustang don’t give you any opportunity to make changes in the rear, but there are many cars with independent rear suspensions that have a lot of adjustability built in.
There are, of course, other changes that can be made to the suspension such as lowering springs, anti-roll bars, and up-rate shock absorbers (spring dampeners for those of you in the UK), but an alignment, properly done, can really maximize the car’s potential on the track or autocross course.
Some cars with a rear weight bias, such as the Porsche 911 would not benefit from negative camber at the front since it can be tail happy all on its own. Drivers starting out in track events probably should do so in a car that understeers slightly until they get a few events under their belts.
For my own car I have installed some fender braces under the front fenders. These provide a surprising amount of stability to the front suspension, and on my car, evened up the front camber settings so that I now run a negative 2.1 degrees of camber. Caster is not adjustable on my car. I run a little less camber in the rear so that I can take advantage of the all wheel drive’s ability to rotate the car without getting too tail happy. Toe is another critical setting and I run zero toe on the front with just a bit of toe-in on the rear.
Just prior to heading up to the event Friday afternoon I’ll change the rotors and brake pads to the track compounds and flush the brake fluid. I like to use the Ate brand of brake fluid on the track as it can deal with heat very well and is compatible with my brake system.
Packing for track days means adding my driving suit to a shirt and a pair of jeans that will carry me through a couple of days. I also pack my helmet, track shoes, and driving gloves. I have a few tools, but since Performance Chassis has a set of tools in the truck I won’t need much for my car.
This trip I want to shoot some video. I have a new GoPro video camera that I want to try out and I think that north course will be good for that.
I’m looking forward to next weekend.