Autocross Line Question

Hello good GRMs and autocrossers. I come to you today with a question about the proper "racing line" to take through this autocross course. I'll be driving it this Sunday and would like to know the correct way to go through here. This will be my 4th autocross event.

You will notice on the map that the recommended line is traced in black throughout the course. I'm asking here because I don't understand why that is the recommended line rather than the red line I drew in. As far as I understood, the best autocross line is usually the shortest... so why the wide line?

Any insight would be appreciated greatly.

Also, if it makes any difference, my car is RWD and underpowered. 1997 240SX

I'm no Solo National Champ, but the wider line (black) will allow you to carry more speed though the corner. If you are cutting it as close as your red line indicates, you'll likely be scrubbing more speed, as you'll be cornering more sharply, with more steering input. Also, try to "straighten" out the corners as much as possible. If you look at the black line again, you'll see that it's basically a straight-a-way for a good portion of the turn. This will allow more speed than a tighter line.

Shortest may seem to be the best but often, wide will alow you to keep up speeds.

Is that truly a "recommended line", or more of a "Here's a visualization of a clean line"? That said, I think I would be on the black line - my thought is that you'd carry more speed through the slalom sweeper on the black line - the kink in the red line coming out of the slalom sweeper looks relatively sharp, and you'd be able to use less steering input following the black line, which would result in preserving more momentum.

I could, however, be totally off, which would explain my complete and utter mediocrity at autocross.

I'd try it both ways. Their suggested line makes a fairly long straight between the 2 double cones inside the 4-cone wall, then adjust speed so you're accelerating through the pair of 4-cone walls w/ the long outside wall. Be very smooth and try to maintain speed. Don't be "Mister lightswitch throttle". On the side-optional slalom I'd start right for a better setup for the fast bit that comes after.

This will help give you a PhD in autox.
https://grassrootsmotorsports.com/forum/grm/video-training-autocrossing-with-dick-turner/33988/page1/

motomoron wrote: I'd try it both ways. Their suggested line makes a fairly long straight between the 2 double cones inside the 4-cone wall, then adjust speed so you're accelerating through the pair of 4-cone walls w/ the long outside wall. Be very smooth and try to maintain speed. Don't be "Mister lightswitch throttle". On the side-optional slalom I'd start right for a better setup for the fast bit that comes after.

Thanks everyone for the suggestions.

I really like the idea of going right on the slalom to set up for the fast bit after - right side beginning it is.

I can see that going wider would result in more momentum. I think when looking at a map I tend to underestimate the radius difference between a wide vs. tight line and as a result underestimate how much speed the tighter line would scrub.

The wide line after the box chicane going into the slalom seems totally excessive to me, but I guess it is to gain speed on the slalom which is more or less treated as a straight.

Is there any general theory that applies here? Treat long sweepers and slaloms as straights? Sounds doubtful, ha.

Think about this: The straighter the steering wheel, the faster you can go.

So a big arc is a faster than a small one. Straights are faster than turns.

Of course, variables can come into play. I remember once taking a really wide arc. Turns out I was the only one who went out there, so it was full of marbles.

motomoron wrote: I'd try it both ways. Their suggested line makes a fairly long straight between the 2 double cones inside the 4-cone wall, then adjust speed so you're accelerating through the pair of 4-cone walls w/ the long outside wall. Be very smooth and try to maintain speed. Don't be "Mister lightswitch throttle". On the side-optional slalom I'd start right for a better setup for the fast bit that comes after.

And in review, I would take the opposite approach - though I do strongly recommend trying it both ways.

I think going left at the first cone of the optional slalom allows you to carry more speed from the preceding turn into and through the slalom. Then, at exit, I suggest widening your red line a bit to allow a smoother, long-radius, double-apex left that connects with the next 2 gates in the next segment. You would make the first apex of that turn somewhere near the beginning of the wall of cones at left as you enter the big D.

^ Am I reading your post wrong or are you running the course backwards?

Its really almost impossible to try to pick out the correct line looking at a course map. There are just too many variables. You've mentioned one - your car. As a general rule, lower powered cars tend to get better times by keeping a close, tight line. But that can vary depending on whether the car over or understeers, how much tire you have, how quick the transitional response of your car is, the camber and grip level of the pavement, the weather, etc., etc. etc. There are dozens, sometimes hundreds of variables when you put a given car, given autocross course and given driver together on any given day.

Here's the best advice I can give you: Get as much exposure to the course as possible. Walk it as many times as you can. If your club allows passengers, try to hitch a ride or two with an experienced driver (this is especially valuable if they have a vehicle similar to yours). Try to have an experienced driver ride with you, get their feedback on your lines and approaches. Get a work assignment where you can see as much of the course as possible without neglecting your assignment. If seeing the whole course is impossible, try to get assigned to whatever part of the course seems most challenging. (Looking at the map, I'd say near the slalom and the transitions in and out it) Track maps are helpful to memorize the general flow of the course so you don't have to think about whether you are headed left/right/straight coming out of an element, but they aren't very useful in isolation for designing lines. Some corners/elements will be tighter than they appear on paper, and others may flow much better than expected. This course looks fairly straight-forward. Have a plan in mind, but be willing to change it, even mid event. Hopefully, you will get a significant number of runs. If so, try a tight line vs. looser line. Start the slalom left, then start it right, etc. etc. and see what the time slips tell you.

When you do your course walks, take your map and find the guy or gal with the biggest hat and follow him/her. . Hopefully he/she drives a similar car, but even if not there can be a lot of potential to spot things you might not otherwise see until you get your first run.

I think the black line is just showing the direction of the course, not necessarily the suggested line. Some folks can look at a great course map like that without a line and still can't figure it out.

In my opinion, the black line is correct until the exit of the 2nd box on the lower right corner of the map. I assume the shaded part inside the oval is where it transitions from banked to flat track, but I would take a line between the black line and your line into the optional slalom. I don't see a reason to swing out that wide unless you plan on going left into the slalom. Try the slalom both ways and see what works. One way is faster going in/ slower coming out, and vice versa. Personally I would probably go in on the right side, but you just don't know until you see the course in person.

The rest of it looks pretty good. The last section in the parking lot needs to be kept tight and tidy.

quite often tight is quicker ... in the case of the sweeper (and the approach to the sweeper) tight wouldn't be the quickest way ... being able to be WOT coming out of the slalom will push you towards the outer edge (as the black line indicates) .. following your line will require you to lift way before you'll have to lift if you follow the black line ... same for the finish of the sweeper ... by allowing your speed to drift you to the outer edge again as you come to the last 2 cones of the sweeper you are pretty much turning the end of the sweeper into a straight line making it easier to get onto the optimum line for the optional slalom

edit: if you try your red line, and find that you don't have to lift, brake, or use way more steering than with the other line, then you probably will be quicker on the red line ... but I'm betting the if you're up to pace, the black line will be quicker

c0rbin9 wrote: ^ Am I reading your post wrong or are you running the course backwards?

Nope, you're correct; I'm a moron. Sorry. However, my point basically stands in the correct direction as well. I agree with you, go right of the first cone in the optional slalom. However, I would still loosen up your red line a little at the base of the D. Make a nice smooth line from the next to last gate of the D through the last gate, apex well past the end of the line of cones, and a nice snake line through the slalom and into a well-rounded left. By the time you get to the lower left corner of the shaded part, you should have completed your right turn and be just tipping into the left around the first slalom cone.

If there's one thing I have learned, it is that you should almost NEVER approach a course with a plan to add distance. Period. It is so rare for it to really, truly be the faster way that it is not worth considering until you get into that element on your first run and find that you are actually driving it too tight and slow. If that is the case, fine, open it up and carry more speed. You've got 2+ more runs to figure it out. But if you run the wide/carry-speed line from the very start, it'll feel OK and so you'll keep doing it and will have no idea how much time you are leaving out there.

(This applies mostly to low power and non-r-comp cars, and does NOT mean you should go to the other extreme and drive from cone to cone with jerky steering inputs. Just don't add excessive distance.)

For that picture, I wouldn't even attempt to decide between red and black until I am on the site and walking the course. Furthermore, the entire red/black section until the bottom of the 'D' I probably would not decide until in the car and feeling it at speed. The exit at the bottom of the 'D' and slalom entry side choice should be evident when walking the course. Not from your computer screen now, though. A few cones moved a few feet makes a big difference, so going into it with the preconception that "I need to go right" will mess you up mentally when a cone has to be moved due to a pothole or drainage grate or something and the course turns out to be faster entering left.

Duke wrote:

c0rbin9 wrote: ^ Am I reading your post wrong or are you running the course backwards?

Nope, you're correct; I'm a moron. Sorry. However, my point basically stands in the correct direction as well.

Well your way would have been correct in that direction so at least we know you're paying attention. :p

Duke wrote: However, I would still loosen up your red line a little at the base of the D.

Makes sense. That's now two people who have said to take a wider (but not too wide) line into the slalom (you and Stoolpigeon).

kazoospec, your point is well taken about the limitations of trying to pick a line through the course with just a map. My goal is to really ramp up the learning curve at my first few autocrosses and this is part of the pre track day homework that I do.

FWIW, I've driven at this track once before, but not this same setup. Right now the plan is to probably take the wider line and see how it works. I'll be looking to make it a double apex corner, the first apex being opposite the first four-cone wall, the second being towards the bottom of the D.

I'm just freaking out at the prospect of seeing a course map before the morning of an event

You know, I was wondering how common/allowed it is to have maps days in advance of the event. Both of my local autocross clubs upload course maps to their websites' a few days before the event.

I'm no national driver, but I did sleep at a Holiday Inn Express last night.

The black line might be using the idea that you can get to the throttle earlier and brake later, thereby embiggening the time you can go fast.

Go ahead and make all the plans you want. We all know what happens to those as soon as you pull out onto the course. E36 M3. E36 M3. Aaaaaaahhhhh! berkeley. berkeley. E36 M3. Aaaaand done!

I'm no expert, but in my years autocrossing I usually saw the fastest guys taking the shorter line, which seemed counter to what I'd been taught (wider being better coming out of the last turn).

snailmont5oh wrote: Go ahead and make all the plans you want. We all know what happens to those as soon as you pull out onto the course. E36 M3. E36 M3. Aaaaaaahhhhh! berkeley. berkeley. E36 M3. Aaaaand done!

HAHAHAHAHA! That is exactly what happens!

CyberEric wrote: I'm no expert, but in my years autocrossing I usually saw the fastest guys taking the shorter line, which seemed counter to what I'd been taught (wider being better coming out of the last turn).

By taking a classic "racing line" instead of hugging the inside, you're trading off a longer distance for a higher average corner speed. This actually makes the corner take longer, it's just that in road racing you usually have a straight after the corner and that higher corner exit speed pays off because you carry it down the straight. Straights in autocross are a lot less common and when you do get one it's usually very short compared to your average road course. This changes the tradeoff -- it's no longer obviously a win to spend more time in the corner to get a higher exit speed if you're just going to jump on the brakes half a second later to enter the next corner. Whether or not the wide entry/exit is worthwhile depends on a lot of things like the car, course, grip level, etc.

mainly you need to experiment ... more often than not tighter IS quicker ... that said, keep in mind that what is the standard isn't always the best ... that's why you run both ... if you find yourself pinched and having to make really sharp moves with steering, braking, and throttle control, then try the wider at certain spots and let the clock tell you which is better

and I realize that at your lever (5th event you said ?) it's hard to get the feedback you need ... that's where riding along with some serious fast drivers really helps ... I don't know how syrsbinus your group is ... but the more rides you can get the better

but mainly ... have fun