In case you know nothing about autocross, my current motorsport of choice, hopefully this post will get you up to speed (pun intended), so this blog might be a bit more meaningful.
At the most basic level, autocross is driving around a course laid out by cones in a parking lot, and competing for the fastest time. Each cone you hit adds 2 seconds to your time, and every event has a new and different course. Length/time of a course is typically between 30-70 seconds, but varies widely based on course design, and the size and condition of the parking lot in which the event is held. Thus, the goal is to get through the course as quickly as possible, without hitting any cones. As a vast over-generalization, the closer you are to the cones, the less distance you have to travel, and the less time it will take. Your time will also be rewarded by carrying as much speed through slaloms, turns, and straights as your vehicle can handle (without losing grip and/or spinning), and minimizing your time on the brakes (by braking hard and late... but not too hard or late).
Autocross offers a safe environment to test the limits of your vehicle, and learn how to handle it under extreme, or non-ideal conditions. I absolutely recommend everyone to autocross at least once or twice- if not for the appreciation of driving, than for a very important lesson in safe handling and vehicle dynamics which can be applied on the streets for accident prevention and avoidance. The SCCA even partners with an autocross-themed "Street Survival" School aimed at teens, to help them become safer drivers. At most events, cones are the worst thing you can hit, and the risk they present to you and your car are basically null.
This would have been my fastest run at 2017 SCCA SOLO nationals, but that cone added 2 seconds to my time.
In short, autocross trains and tests your ability to perform at every limit of your vehicle. It's an event won or lost by thousandths of a second, so every single input you give the car, matters.
Now you might be thinking- every vehicle has very different capabilities, so surely vehicle selection matters more than a driver's experience! And sure enough, if you're competing at a national level, against vehicles that are designed or set up specifically for autocross, it might be hard to keep pace in an un, or under-prepared vehicle. But until a driver is knowledgeable and comfortable with using a vehicle at its limits, and sticking to the fastest "line" throughout a course, it's going to be very difficult for them to achieve peak performance, even in a theoretically perfect vehicle. Thus, while autocross certainly emphasizes the relationship a driver has with their vehicle, that vehicle isn't going to drive itself! It all comes back to the driver.
If you aren't sure what I mean by "line" above, it refers to the exact path you drive on a course. Think of staying tight inside a corners vs. swinging out wide, or taking a 90* turn with an increasing or decreasing radius. There's typically a "fastest way" through every turn based on factors like: how tight it is, how fast you are going, what came before it, what's coming after it, and how fast your vehicle can accelerate or brake, etc. Learning optimal vehicle placement on course is a huge part of learning how to excel at autocross, and as you may have just gathered, can get complicated. Thankfully, there are many resources and schools available to help drivers of all ability levels learn this skill. I'll be touching on some of these in later posts.
Going back to vehicle selection and set up topic, I need to give a quick introduction/explanation of how the SCCA attempts to equalize the differing abilities of the vast diversity of vehicles available. There are approximately 49 different autocross "classes" that a vehicle can run in, across eight-ish different levels of preparation. The exact class your vehicle falls into depends on what make/model/type of vehicle it is, what performance-enhancing modifications it has done to it, and what tires it is on. I'm not going to delve into all of those here, but the takeaway, is that if you want to race your totally unmodified car at an autocross event and be competitive, you can!
There is system of time multipliers which serve as a handicap (officially called PAX, or sometimes index), set out to equalize the expected difference between say, an unmodified Mazda3 driving on street tires, a heavily modified Porsche GT3 driving on racing compound tires, and a purpose-built tube chassis autocross machine. (Did I mention that tires are almost certainly the #1 most important modification on a vehicle in autocross?? Or on the road for that matter!!) Obviously, given equally talented drivers, the tube chassis car would have the fastest (smallest) time, and the Mazda would have the slowest (largest). But, each of these 49 classes has a different multiplier to aid in comparing it to other classes. So while the tube chassis car may have gotten the course done in 40.000 seconds, and the Mazda3 in 51.000 seconds, the time from the tube chassis car would be multiplied by 1.000, and the Mazda by 0.781 (the most generous of all pax), resulting in a time of (51.000 x 0.781 =) 39.831 vs the (40.000 x 1.000 =) 40.000- thus beating the tube chassis car.
| SS | 0.817 | SSP | 0.852 | XP | 0.884 | AM | 1.000 | |||
| AS | 0.814 | ASP | 0.848 | BP | 0.860 | BM | 0.956 | |||
| BS | 0.808 | BSP | 0.846 | CP | 0.847 | CM | 0.890 | |||
| CS | 0.805 | CSP | 0.857 | DP | 0.858 | DM | 0.895 | |||
| DS | 0.794 | DSP | 0.835 | EP | 0.850 | EM | 0.894 | |||
| ES | 0.787 | ESP | 0.828 | FP | 0.863 | FM | 0.904 | |||
| FS | 0.797 | FSP | 0.819 | HCR | 0.812 | FSAE | 0.958 | |||
| GS | 0.786 | |||||||||
| HS | 0.781 | SSR | 0.838 | SMF | 0.839 | KM | 0.928 | |||
| HCS | 0.791 | SM | 0.853 | JA | 0.855 | |||||
| SSC | 0.806 | CAM-C | 0.816 | SSM | 0.871 | JB | 0.825 | |||
| CAM-T | 0.807 | JC | 0.718 | |||||||
| STS | 0.810 | CAM-S | 0.831 | |||||||
| STX | 0.813 | |||||||||
| STR | 0.823 | |||||||||
| STU | 0.824 | |||||||||
| STP | 0.815 | |||||||||
| STH | 0.811 |
Rick Ruth PAX/RTP Administrator: https://www.autox4u.com/announcements/2018-pax-index/
The handicap/pax multipliers are statistically re-examined every year based on the results from nationals, and altered slightly where needed. Of course, cars running within the same class (2 different Mazda3s on street tires) will have the same multiplier, so they can just compare their "raw times," or their actual, un-multiplied times (51.000 seconds for the one Mazda). The takeaway about autocross classing through the SCCA, is that you don't have to spend a bunch of money to be competitive.
The flip-side: if you like modifying your car, you do have to keep a close eye on the rules so you don't accidentally land yourself in a class you'll need another $10,000 worth of modifications to be competitive in. For example, my Mazdaspeed3 was that way because it had a bigger turbo that stock. It was a fun turbo, but that alone landed that car in a class at the forth level of preparation ("Street Modified" or "SM")- something I'd never realistically be able to be afford to be competitive in. The pax multiplier for that class is very high and unforgiving, reflective of all the modifications allowed for those cars (only one of which is an upgraded turbo). That means big, unrealistic expectations on the car's ability to perform, since it didn't have many of those other performance enhancing modifications allowed. I recently removed that turbo and went back to stock, just so I could back the car off to the class at the second level of preparation- "Street Touring" or "ST" ("STH" or "Street Touring Hatchback" to be specific).
The Mazdaspeed6 I drive is in the third level of preparation- "Street Prepared," or "SP." Further, it's in "ESP", to place it with cars that would be similarly capable with all the same allowed modifications (the E doesn't stand for anything)- as opposed to, say, "CSP," which is the class where Mazda Miatas with all those same modifications belong. ESP and CSP are no closer related than any other two classes though, in that their times are comparable only through each class' pax times. The same is true for ASP, BSP, and DSP.
Here you can see the lettering "ESP" to designate our car in E Street Prepared. The "L" here is because I chose to run in the "Ladies" class at this event. Ladies classes were created to encourage more women to participate and build relationships, but women are able to choose between running in "Ladies" or open class. I'm sure I'll come back to this topic in a future post.
This is as simple as I can make an activity with a 300+ page rulebook. Still fairly complicated for driving around cones in a parking lot, but hopefully this helps. Please feel free to leave comments if you are seeking any further clarifications!
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