Monday, October 04, 2010

Primer: Autocross

(I've recently had call to describe autocross to a few people, so I'm placing this introduction here to have something to point to in the future.)

The Setup

Autocross is perhaps the most accessible form of motorsport. In auto-X, a course it set up, using traffic cones, on an open expanse of tarmac or concrete, usually a parking lot, but sometimes an airfield. A new course is used at each event. Each driver runs the course, effectively alone, attempting to minimize his or her time while not hitting any cones. A penalty, usually 2 seconds, is added to the driver's raw time for each displaced cone. The driver's best net time, after several attempts, is compared against the best times of drivers of other similarly capable cars. The courses are designed to be very challenging for the car and driver. Typical autocross runs have more turns per minute than a lap of a Formula One race. When not driving or preparing to drive, each competitor must work the event, either reseting downed cones, recording times, directing drivers, safety-inspecting cars, or doing whatever else is needed.


The risk of car damage or injury is very low for three reasons:
  • The course is defined by cones, so, as long as you don't go too far afield, there's nothing to hit but orange rubber pylons. The courses are designed to keep cars away from light poles, curbs, and other fixed obstacles.
  • The coursees are kept very tight, which keeps speeds in check. For many cars, most courses can be run without shifting beyond second gear, though some vehicles will need third for short periods. Indeed, one figure of merit for an autocross car is its top speed in second gear.
  • Cars are released onto the course at intervals of 20 or 30 seconds. As a result, the odds of a two-vehicle collision are low.
All the organizations that I've run with require each vehicle to pass a technical inspection. To pass, the car must have all loose parts removed from the interior or exterior, and the car must be in good mechanical condition. I've worked as a tech inspector at numerous events, and the most common cause for rejecting a car is a loose battery; that's a problem that can usually be fixed in a few moments, allowing the car to be reinspected and passed.

All the orgs I've competed with also require the driver to wear a Snell-rated helmet, ether M (motorcycle) or SA (special applications, meaning auto racing). Most orgs seem to accept the current rating (currently 2010) and the two previous ones (2005 and 2000).


Depending on the organization, location, course design, car, and driver, each run takes from 30 to 80 seconds, though most of the events I contest have 40- to 60-second runs. The number of runs each driver gets depends on the organization, the duration of the event, and importantly, the number of drivers that must be fit into the event. Bigger events, with 150 or 200 people, usually offer 4 runs, while smaller events, with 20 or 30 people, might give each driver 20. Numbers like 4 and 5 are most common.

And you might be there for 3 or 5 hours. So, for the events I go to most, the ratio of waiting to driving is about 60:1. This fact is my least favorite aspect of the sport, but I've made peace with it. I try to find a work assignment that keeps me busy rather than bored, and I focus on the non-driving activities that I enjoy most: the car preparation, the socializing, the "bench racing," and so on.


Numerous organizations host autocrosses. In any given metropolitan area, there are likely a handful of such clubs to be found.
  • The club that organizes the largest number of autocrosses is probably the Sports Car Club of America. SCCA calls their version of autocross "Solo," and they also offer a version called "ProSolo," which features two cars running head-to-head and a drag-race start. You can read more about ProSolo and see an annotated video of my last Pro event here. In the area around the nation's capital, the local chapter of SCCA is the Washington DC Region. You can sign up for the WDCR Solo mailing list here.
  • The National Auto Sport Association is another national organization that runs autocross envents, which they call NASA-X, pronounced NASA-cross, races.
  • There are a number of smaller motorsports clubs around the country. In the DC area, the most popular are the Capital Driving Club and Autocrossers, Inc., which is an affiliate of the SCCA's Washington DC Region and uses SCCA rules. You can sign up for the AI mailing list here.
  • A number of marque clubs also host these events. At least in my area, the BMW Car Club of America, the Porsche Club of America, and the Mazda Sportscar Club of Washington all put on races.


Each club has its own system for classing cars.

  • SCCA, being the most popular group, has the most byzantine ruleset. It's a two-dimensional system; one axis is based on the stock performance of the car in question, while the other is how modified the car is. I don't have the room to discuss the SCCA classes here, but I hope to add a post about that in the future.
  • NASA uses a points system, where each car is awarded a certain number of points based on its stock performance capability and accrues more points for each modification. Each class spans a range of points values.
  • The CDC uses a simple indexing scheme based on power delivered to the wheels, weight, and treadwear rating.
  • The BMW CCA, at least the National Capital Chapter, uses a matrix approach, like a streamlined version of SCCA's, for BMWs. For non-BMWs, it applies a very simple, four-class structure based on engine displacement, engine type (piston or rotary), induction type (natural or forced), and, of course, treadware.
  • The MSCW, which puts on very relaxed, casual events, imposes no classes at all.


Several clubs offer schools that teach you everything you need to know to compete in and work during an autocross. In my area, the Washington DC Region of the SCCA offers several Level 1 and Level 2 schools throughout the season.


The cost varies form org to org, but, for single-day events, 25 to 35 dollars is normal, at least in the DC area. It's very affordable as motorsports go.


This video, a class project of someone in the San Diego Region of the SCCA, covers some of what I discussed in this post. Keep an eye out for the lime-green, rotary-powered Bugeye Sprite.

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