A Novice Guide to AutoCross

[Carrera26]

I was having a huge problem getting rotation. It really came down to the fact that I didn't have enough energy in the chassis. You just have to be going pretty darned quick to get it turning, so you just have to bomb into that corner and trust that the rotation will be enough to get you through the turn on-line.

The other thing about LFB is that it's really surprising how much just a little brake pressure can effect the car. If you give it a lot of brake, you will slow down the car too much for it to have the energy to rotate. Most of the time when I am using it for rotation, I am barely applying pressure to the pedal. Maybe 5%, probably less. Even after I learned, it took several events to force myself to commit myself fully enough to go in at speed and use so little brake. It feels totally counter-intuitive when you are trying as hard as you can to be smooth and stay on line. I still think I have a ways to go on really getting it near 100%.

The instructors at Evo were using rotation through 15' slalom cones if you can believe that. I don't think that there was a single turn where they didn't get a little rotation, just because they kept the velocity so high that the rear end of the car was a steering aid instead of a hindrance. They were almost violent with the inputs, but smooth and controlled at the same time. Even through the first slalom, look at my video and compare. On my initial run I was smooth and constant all the way through, but relatively slow. When the instructor climbs in, the changes in direction are much sharper. By letting the car settle, then yanking it, he was able to set the rears loose JUST ENOUGH to radically increase it's ability to change direction but get settled quickly enough to do it for the next cone. My jaw was quite literally hanging open about 5 seconds into the run. Felt like they had secretly thrown R-comps onto my car. I simply couldn't register how much grip he was getting, and it was all because he didn't have to fight the rear to get it. And this was in the friggin rain!!!

Instead of going 0% steering to 30% in a smooth and constant way, he smoothed his way to 5%, and then skipped directly to 40%. Of course, he only did this where appropriate, but it was appropriate in a lot more places thant I had imangined.

I learned this very important factor. There is only a limited amount of grip the front tires can generate, and in normal circumstances they not only have to pull the front end around, but also the back. The rear tires actually fight the change in direction. If you seriously reduce the grip from the back fighting the direction change, significantly more grip can be used to turn the car.

Try this next time you are driving. Turn it just enough so that you feel the weight settle on that side. Then very quickly move the wheel to the full amount you need from the turn. You'll feel it react much quicker, because you have eliminated that fraction of a second it normally takes to shift weight, and because it's already settled you'll find that you have a lot more grip and can changed direction much faster. You'll also feel that it's more controlled and settled all the way through...

Actually, this sort of thing applies to the gas and brakes as well. You don't want to "surprise" the chassis or any other system. If the system is unloaded and you quickly shift the weight, then just by the laws of physics the system will "hit" the limit with more inertia, and that system will be less able to cope after the initial shock. As the point is for the system to resist that energy as much as possible, anything you can do to reduce the energy going into it (and get the same result) is a good thing.

Note: I have deleted my really crappy analogy and can't think of a really good one. Hopefully you get what I am saying without it and/or somebody else will think of something better.

That's the physics behind the rotation as well. The rear is a little behind the front, so if you hit it with a sudden bit of force, it's much easier to knock off-line than by smoothly piling more force on top of it...

Never meant to go that long, but there it is...I thought I'd repost this in here...

[WD40]

Special thanks to FF member DirtyDeeds for the following links.

Articles from GRM (Grassroots Motorsports):
Choosing Your Next Set of Brake Pads
The Inside Scoop on Anti-Roll Bars
Top 10 Driving Mistakes and How to Correct Them

And, a couple more assorted links:
Listing of Autocross clubs across the USA
Allowable Mods by Class (Autocross)

[JBrotbeck]

And here it is again in case you haven't seen it in the other eleventy billion places I've posted it:

The famous "Old Dominion Region SCCA Self Classing At A Glance Uber Chart"
NOW WITH HIGHLIGHTS! --->clicky---> link to chart

[Dcl2049]

I've been doing this for about half a year now and have learned tons in that little time, so I thought I'd throw in my 2¢... Maybe I can help out the auto people a little more.

For you auto people, go with O/D off. I'm not sure if this is 100% true, but if I floor the car around the day before the race, it feels like the car learns that style and tends to hold higher revs a lot longer and shift at higher RPM than when I drive like a granny. This can help in certain turns where you don't want it upshifting when you let off the gas a little. Also, you can learn to modulate the pedal to get it to shift around in certain ways, but it's hit or miss most of the time. There's no formula to it, you just have to kind of "feel" it. In the really slow turns when you have to slow down a lot, it will usually go up a gear when you let off the gas. To counter this, I usually punch it right before the apex so it will shift back down, then let off to a reasonable level so I don't take off before the middle of the turn.

About my tire pressures... I used to run at about 42psi in each, adjusting the rear as I see fit... but recently I've been running with ~38. I'm not sure if it's my tires (BFG G-Force Sport) but I don't go up on the sidewall and I feel much more confident driving with the lower pressures. I think it's gripping a lot better, as I would understeer/slide a lot more often when my pressures were higher.

[thehubster]

hey does anyone know were i can find all of the locations of autox events?

[WeeAsp]

Originally Posted by thehubster

hey does anyone know were i can find all of the locations of autox events?

The most comprehensive site I've ever found.

http://www.myautoevents.com/pls/mae/frmMain.Show

[sqrly]

very informative

[WD40]

Here's another great site with graphics and plenty of information for novices to experts:
http://www.wtfstables.com/rmsoloschool

[illinipo]

Here's probably a common question from novices...

I'm on the verge of becoming addicted to cones and have planned my first event. I have looked at the class rules and find that what I thought were minor mods (65mm tb, mild grind cams, etc...) have put me into the toughest class, SM. Going all out (turbo, R-compounds, etc) is not in my budget. Should I still go for it just for the fun factor? Or will I start wishing I never did those "minor" mods?

From what I have seen, the beauty of atuox is that even though I dont have the HP to keep up with the evo's and wrx's in a straight line, I can still be competitive in solo II SM with my "minor" mods. Is this true?

Thanks :)

[Carrera26]

Absolutely. Trust me, as a novice, even if you had the best built SM car in the nation, you would still be getting beaten by stock class Miatas or Mini Coopers with experienced drivers. Don't worry about classing whatsoever, just go out there and have fun.