Autocross / SCCA Solo 201 - How to Improve

Discussion in 'Track Day, Solo, AutoX & Sanctioned Road Racing' started by JMcDonough, Mar 22, 2020.

  1. JMcDonough

    JMcDonough Member

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    If you have never autocrossed before, see the Autocross 101 thread.

    So you've done this a few times, maybe a season or two and you want to get "better", whether its the driver, car, or both.

    Autocross 201:

    What matters the most, in order:
    - Driver performance
    - Tires
    - Car (dimensions, weight, drivetrain layout, wheel size, etc.)
    - Alignment & suspension
    - Other stuff
    - Power

    Read that list again. And again. Hopefully it sinks in some.

    Let me explain it in a little more detail. All of those are important. The people winning Solo Nationals, etc have them all mostly figured out. Leave out one or two, and you can be in the trophies, but aren't going to win.
    At most local events, and even at many national tour events, you might be able to win your class with any varying degree of competency in them. Don't let that fool you into thinking you (or anyone who uses them as absolute justification of their prowess) have it all figured out.
    Within each category, there's a wide range. Are you on the 100% best tires for the day/surface/temp or tires that are capable of within 0.2s of the 100% best for that day? Or Tiger Paw All-seasons that are 3 seconds off the pace even with Tom O'Gorman behind the wheel?

    Where to start:

    Driver performance
    Want to know how much time you have to gain there? Get a good local driver to hop in and set baseline. Have that person co-drive at an event, or at least take some timed "fun runs" in your car. If at all possible, also ride with them. This can be hugely helpful for a number of reasons.
    1. If their time is lower, instantly you know at least how much you have on the table in driving.
    2. They have feedback for how your car drives. They probably know at least somewhat what a good autocross car feels like. They will most likely be able to point out any glaring deficiencies (grip, balance, brakes, etc).
    3. Riding with them may make you realize that your car can do something you didn't know was possible (my brakes can stop the car that quickly???).
    4. Their approach/line choice may be very different in some area, allowing you to better identify flaws in your approach or execution.
    5. Have that person also ride with you and provide pointers.
    Now, ideally you have full data and video of exactly where and why the faster driver is faster but that's not always the case. You may still need to do some experimentation on if the other person's line choice really was better or if the time was gained elsewhere.

    Driving schools are a great way to get this type of instruction in a very intentional manner. Most local regions will have at least 1/yr. There are organizations that put them on nationally (SCCA Starting Line, EVO Performance Driving School, etc). Most all of these are worth the time and money to attend. Local ones can be spotty with the instruction part, but you'll always get more seat time than a regular event.
    Schools are a great way to speed up the learning curve and try new driving techniques/approaches in a lower pressure, controlled environment.

    No matter who you are, there's always room for improving your driving. Realizing this is important because you always have to be working to improve to keep up with other racers who are improving. Get complacent and you will start dropping in the standings.

    Other things do matter, just not as much as the driver. That said, the driver is only one piece of the puzzle. Put the best driver in a terrible car and lots of decent drivers will beat them due to better equipment. Some won't, but some will. Point being, again, the other items in the list matter, too.

    Tires
    People who do this competitively generally obsess over tires. Why? They matter. A lot. No, your 400 tw "sport" tires are not "good" at autocross. Here's the current list of good 200+tw autocross tires:
    - Yokohama Advan A052
    - BFG Rival S 1.5
    - Bridgestone RE-71R
    - Falken RT660*
    - Goodyear Eagle F1 Supercar3*
    *jury is still somewhat out on these last two.

    Next tier examples (0.5s+ back of the top tier on a typical auto-x course):
    - Falken RT615k+
    - Dunlop Direzza ZIII
    - Hankook RS4
    - Michelin Pilot Sport 4s/Pilot Super Sport
    - Nexen N Fera Sur4g

    Even further back (unless the course is wet or very cold)
    - Anything in the "Max performance Summer" and lower tire categories

    Tire Rack and Grassroots Motorsports both test Extreme Performance tires often, typically annually. They are both a good data point to consider, but you have to be careful when interpreting their results. GRM does a good job of helping you understand that in their writing. Know that Tire Rack autocross lap times are a composite, at a fixed pressure, typically after many runs back to back to back. It's not the single best lap their best driver produced.

    As an intermediate autocrosser looking to improve you basically have one of two options:
    1. Put one of the 3 good tires on your car (they all have their pros/cons, I'd buy the Yokohamas if I had to choose a tire today).
    2. Don't put one of the 3 good tires on your car and constantly guess how far back you are of the leaders as a result. A good co-driver can help with this. But if you want to eliminate an excuse for your performance, buy good tires.

    Generally speaking, picking one of the "good" tires and running them will be better than wider/bigger not "good" tires. This holds true within maybe 30mm/1" of tire/wheel width. More than that, a wider 2nd tier might be faster. Might.

    Even once you've picked your tire, there's still more to do to get the most out of them. They all drive a bit differently, handle temperature a bit differently, handle surfaces a bit differently, wear a bit differently, like different pressures, like different suspension settings, etc. Being on a "good" tire gets you in the ballpark, but that's only ~75% of the battle with tires.

    R-compound tires/slicks/etc are their own can of worms but generally subject to much of the above. I have limited experience with them, but for DOT radials the list is short: Hoosier A7. For prepared or modified class cars, there seem a specific tire or two you want depending on the class/wheel size. Hoosier or Avon. I don't know the specifics on these.

    Many an autocrosser has been fooled by thinking their "good" tires (ones from the list above) were still competitive when they weren't. Age, heat cycles, wear, mold release compound, etc all impact tire performance. Buying someones 3 year old take off RE-71R's with 120 runs and cords showing isn't running a "good" tire. Might be faster than what you have today, but not "good".

    The Car

    Loosely speaking, you see two types of cars at autocross events:
    1. Those that were purchased to autocross since they are or can be competitive in a given class
    2. Those that were not purchased to autocross and are there because their owner wants to have fun in something they already own.

    Why does that matter? Because you are likely in the 2nd camp and competing against people in the 1st group. That means their car is:
    - lighter
    - smaller
    - better weight distribution
    - bigger wheels
    - etc.
    Those things mean you are at an inherent disadvantage. Not necessarily insurmountable, but an uphill battle none-the-less.

    What can you do about it? All depends on what your goals are. Want to focus on driving and ultimate competition? Park or Sell your current car and get a known competitive street class car.
    Want to make the most of your current ride from a competitive standpoint? Pick a class where your chassis can be competitive and prep to the limit of the rules.
    Or make some changes that are the best bang for the buck and enjoy competition between whichever cars are close to you in the standings.
    Or live with what you have and have fun improving despite the disadvantages. No right or wrong answer here in the absolute sense. But some answers are certainly better than others depending what your goals are.

    Alignment and Suspension

    Because tires are so critical to performance, keeping them in their happy place is crucial. I already mentioned pressure, but understeer/oversteer balance, camber, caster, toe, geometry, stiffness, etc all matter. Sometimes a lot.

    This isn't a matter of having the "best" parts on the car. Its a matter of having the right combination of parts, optimized sufficiently.

    Some guidelines:
    - Balance is important because it makes getting the most out of the car possible/much easier. Excessive under/over steer punishes small mistakes and means you aren't utilizing all the tires as much as possible. Balance can depend on how the car is driven, so there's no one size fits all setup. No matter the car, you want some way to fine tune/adjust this between events (better yet between runs).
    - Camber - your front tires want more. Does it look broken? No? Probably want more. Ex: Many SCCA ST class autocross cars (lowered, stiff double A-Arm suspension) run upwards of -4 degrees. Looks broken, but it is fast. Sure, caster can help here, but only so much and it causes other issues. Keep adding negative camber until you go slower. If the car start oversteering due to adding more camber, good, time to add more load to the front tires via sway bar, springs or help the rear by dropping tire pressure back there.
    - Camber, take 2: But what about braking performance with all that negative camber? Eh, most of the time you are turning. Not much time spent braking. Optimize the turning, adjust to the reduced braking (and add rear brake bias if needed)
    - Toe: a little toe out in the front (~1/8") can help. I usually run 0 toe. Changes the steering feel/responsiveness of the car.
    - Geometry: good suspension geometry helps minimize the tradeoffs and compromises you have to make to optimize a given suspension setting. Plenty of books out there on this topic. I'm not an expert, so I'll defer to those. Generally speaking, you can make most suspension geometries work if you either make them sufficiently stiff that travel is limited, or optimize other aspects around them.
    - Lowering: All things equal, lowering the car will make it quicker due to the lower center of gravity reducing the amount of lateral load transfer from inside to outside in a corner. Keeps all 4 tires happier. There's always a limit to how low you can go before other stuff starts to compromise the benefits. Riding on hard bumpstops = bad. Tires hitting the inner fenders = bad. Large amounts of bumpsteer = bad. Excessive roll or other forms of camber loss = bad. If you lower the car a bunch, you have to figure out how to keep those things from outweighing the benefits of lowering.
    - Springs & Shocks: Stiffer springs are usually advantageous since the suspension then doen't travel as much, keeping the geometry in check and preventing the car from riding on the bumpstops. Also helps make the car more responsive to driver inputs, which typically helps. If a car is very delayed in response, you have to lead it more, meaning the feedback becomes disjointed from the input. Corrections to inputs are then delayed and you can get behind on high speed elements more easily. That said, you can certainly go too far in this direction where the car is so stiff, small inputs by the driver or bumps are exaggerated and easily overwhelm the tires. There's a happy medium here (stiffer than you'd want on the street, but not as stiff as riding on a normal bump stop).
    - Springs & shocks, take 2: Shocks play a crucial role in the dynamic behavior of the car. During autocross runs, the car is rarely in steady position, meaning the shocks are almost always contributing to the balance and feel of the car. This is another area where just this subject alone fills many books, but you at least want decent shocks (koni yellow or bilstein) if you are trying to be competitive. Adjustability can be nice, especially to experiment with if you don't know what too much/too little feels like from the driver's seat. Crappy shocks (too soft/too stiff) can ruin an otherwise good car. Most autocrosses favor a digressive valving with good low speed adjustability on both compression and rebound, rebound generally being the more important adjustment of the two.

    As mentioned above, some of this stuff is subject to the driver's preference. Test and tune events are nice to play with these types of settings in a more controlled environment and see what works for you.

    Other stuff
    What does this include? A whole host of other factors that are each generally more important than power. Such as:
    - Seats & seat belts that keep you planted in the car and not failing around, having to use the steering wheel to hold you
    - Brakes that are well balanced and stop the car effectively.
    - Transmission and gearing. Most top level autocrossers run a manual transmission, using 1st gear for launch and 2nd gear for running the course. Needing 3rd or having to go back to 2nd for 25mph turns is pain and usually results in a loss of time.
    - Power steering with a fast ratio box/rack. Makes the job of putting the car where you want much easier. Easier/faster to catch mistakes (ex: countersteering to catch a slide).
    - Certainly more here I'm drawing a blank on at the moment, but lots of little things can make a difference. Cars that are easy to drive are more consistently fast.

    Power
    There's no denying power (really, acceleration) can help improve your autocross time. Obviously getting from point A to point B in less time CAN mean a lower overall time. However, we need to understand the good, the bad, and the ugly of having more power.
    The Good:
    - The giggles. It's fun. Having the ability to hit warp speed with the right pedal tingles the euphoric nerves in the brain.
    - More power can mean higher acceleration, which means more speed sooner, which means less time to cover a fixed distance.
    - Perhaps less of a time penalty if you over slow for a corner.
    The Bad:
    - Makes the car harder to drive and get 100% out of. When the right pedal has the ability to upset the car, you now have to be able to modulate it effectively. HS Mini Coopers do not have this problem. I know, I ran one for a few seasons. The right pedal is basically a switch.
    - The more speed you have, the sooner you have to start braking, the easier it becomes to blow a braking zone.
    - Makes suspension setup decisions more of a compromise. Low HP cars don't worry as much about how to setup the rear suspension to put power down, just how to get the most lateral grip.
    The Ugly:
    - Can become a crutch. If all you do is think about how to get the skinny pedal down more, you are likely not giving enough thought to the rest of the aspects of autocross.
    - It has diminishing returns, even when you consider percentage increases. Going from 100hp to 150hp will help a car more on the clock than going from 400hp to 600hp. This is because you can use 150hp almost all of the time when accelerating. The places on a typical course where you have the car straight enough to use all 600hp (or anything over 400hp) is relatively few.

    So, let's say you've done everything can with other aspects of the car and you think there's time being left on the table in accelerations zones? What to do?
    - Look at the speed range over which you are accelerating (generally 30-60mph). Spec your powertrain to perform well over that range of RPMs based on your gearing (or change gearing in combination).
    - Maximized delivered power over that speed range.
    - Try to make the engine's response as quick and linear as possible (read: large turbos with a bunch of lag are bad for auto-x).
    - Don't go overboard with power of if you do, try to remap/reconfigure the gas pedal to have a more progressive ramp-in of torque. Last thing you want is a 10% change in throttle causing a 80% change in torque.
    - Understand what your intended tires will permit and don't exceed them by too much. 600hp is a handicap if your tires can only handle 400hp at autocross speeds.



    What's the purpose of all of the above info? Look through it and try to identify where the low hanging fruit is on your car/driver combo.

    If you are leaving 3 seconds on course to a mid-pack driver when they hop in your car (or you hop in theirs)....that's what you should focus on. If you can keep up with decent drivers in other cars, maybe the tires are holding you back. Do the brakes lock up and spin the car when you barely breath on them? Fix that. If you have a bunch of issues, start with the items higher up on the list and work your way down.

    The other critical step in this phase of autocross is to develop and set realistic goals. If you know what you want to accomplish (ex: local CAM-T class season trophy, get top 50% on pax, keep up with a buddy in his fox body, etc.), you can better plan and execute towards that goal. Ex: You're within 1 second of being top 50% on pax despite running on Cooper Cobra tires. You don't need to overhaul your whole suspension, put a $2000 set of coilovers on, or add a blower. If you've already taken a good auto-x driving school, buy better tires.
     
    xten, riccnick, G72Zed and 1 other person like this.
  2. riccnick

    riccnick New Member

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    Great read!
     
  3. JMcDonough

    JMcDonough Member

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    Another 201 topic - PAX/RTP aka Index, and while we're at it, PSI (ProSolo Index)

    You can find the official PAX #s here: http://solotime.info/pax/index.html

    There's a whole history around this set of number, how it came to be, how it evolved over time, etc. I won't go into all the detail, but here's what you should at least know:

    Rick Ruth (Chicago SCCA region) is the PAX/RTP Administrator. He does this voluntarily and bases the numbers off of data from local and national events with some discretionary judgement applied in cases like new classes or re-classing of competitive cars.

    The PAX/RTP numbers are biased to asphalt surfaces, since that is what the majority of clubs run on. More on this later.

    The intent or goal of PAX is to allow some level of comparison of times between different classes. We all know a C5 Z06 corvette on race tires should be faster than a stock Mini Cooper on street tires. But how much faster should it be?

    1 second? 2? 0.5? 10?

    Some assumptions that pax makes:
    - "Best" driver is in the car
    - Car is prepped to the limit of the rules (ehh, not always, but mostly)
    - Conditions are "ideal"
    - Course is an "average" autocross course (might be more accurate to say a "nominal" course, dunno)
    - Difference in time is a function of the total length of the course
    - Asphalt surface (certainly bias in this direction, but not all results used are from asphalt lots)
    - A-Modified class always has a factor of "1.0"
    - All classes are slower than A-Modified


    Factors to keep in mind that pax does not and cannot account for:
    - Weather conditions
    - Surface type
    - Course design
    - New tires that are faster than last year
    - New cars making a class faster (it does appear there is some attempt, but it's always a guess as to how much)
    - etc.

    If the pax number were perfect and you could create the average autocross course on a perfect day, the idea is that you could put the best driver in the most perfectly prepared Z06 along with the best driver (not necessarily the same driver) in the most perfectly prepared Mini Cooper and if you multiplied each car's time by the pax index value, you'd arrive at the same exact number. Let's walk through an example of this.

    C5 Z06 prepped to A-Street specs runs a time of 45.738 seconds.
    Next car on course is an H-Street Mini Cooper. The Mini runs a time of 48.024 seconds.

    The Z06 has an index time of 45.738 * 0.819 = 37.459 seconds
    The Mini Cooper has an index time of 48.024 * 0.780 = 37.459 seconds

    Pax then says these cars were driven equivalently, down to the thousandth of a second.

    Where do those 0.819 and 0.780 numbers come from? 2020 values from here: http://solotime.info/pax/index.html (also linked above)

    In this example the Z06 had to be 2.287 seconds faster than the Mini. An A-Mod car would need to run a 37.459 (index of 1.0). Divide 37.459 by the class index of your choosing to see what it's equivalent time is.

    Based on this being a multiplication factor, the absolute time delta grows/shrinks as a function of course length (in time).

    Some general observations I've noticed about PAX over the years:
    - Really good drivers are rarely outside the top ~10 at local events in anything remotely competitive
    - It can be a good guideline, especially when averaged over a number of events and be used as a way to track your driving progression
    - All of the factors that pax does not account for can and do bias the results
    - Some people overplay the significance of it. A lot. It's one measure that's never really "right". Faster on pax doesn't necessarily mean a better driver, especially when the difference is small.
    - Some people don't like to look at pax because they do poorly on it, but win their class. So, they claim pax is "wrong" for their class and continue to believe they are as good of a driver despite being 2 seconds off the true pace for their class.
    - Index results at national events tent to be heavily skewed towards race tire class and certain classes seem to out perform (SM, SSM, SSR)
    - Some of this is likely due to classes (SSR) being stacked with talent
    - Some of this is likely due to race tires have more of an advantage over street tires on concrete surfaces
    - Some of this is likely due to National Tour courses being more open than most local courses. Higher speeds, longer acceleration zones.
    - Similar sized cars on similar tires are good places to use PAX for comparison. Examples:
    - CS vs STR
    - ES vs STS
    - SSR vs SSP/DSP
    - It's generally acknowledged that some classes have relatively soft PAX index for what they are capable of due to the current state of development.
    Side Note: CAM-T is a great example of this. 2020 index is 0.817. Let's compare that to the A-Street index of 0.0819. Nearly identical. Sure, C5 Z06 and C6 Z06 cars rule to roost in AS today. Compared to those car, CAM-T cars can be: As light or lighter, physically smaller, wider wheels and tires, stiffer suspension, and more powerful. On paper, the CAM-T car *should* be faster. I mean, the rules allow you to literally put a C6 Z06 under any CAM-T eligible car and make it shorter and narrower if you want. So why is the pax nearly the same? Turns out, it's really difficult to take a CAM-T eligible car and make it as fast (on an autocross course) as a AS prepped C6 Z06. Then there's the driving part. For a number of (or whatever) reasons, CAM-T hasn't attracted the same quantity of high caliber drivers in cars with capability beyond that of a street class Z06 to prove the PAX should be "harder" than AS.
    - Due to the ability of a few people to push the boundaries of the rules in a given class, the pax becomes exceedingly difficult for other cars in the class. E-Modified is a good example of this.
    Side Note #2: The top EM car in the country is a monster of a machine in a tiny package with a TON of development work, time and money poured into it. The owner/driver routinely puts seconds on the closest competitors (in the dry). So unless Rick Ruth wants that EM car winning pax at every event it attends, the pax has to be set based largely on what that car has shown the class is capable of. All other EM competitors suffer on pax standings as a result.

    Oh, then there's ProSolo Index (PSI). Just like pax, but maintained by whomever is the head of SCCA ProSolo. It gets used in combined or bump classes to actually determine the winner for SCCA ProSolo events. I don't know exactly who all is involved in coming up with the numbers. I think generally they start with standard pax and attempt to account for:
    - ProSolo launch capability and initial straight line potential (Prosolos have a drag strip style start with typically a ~200ft straight, on each side)
    - Concrete surface (most, but not all ProSolos are run on concrete)
    - ??​

    If you compare the two, you'll see classes with higher HP and or AWD tend to have a "harder" index vs other classes. Street tire classes also get a "softer" index relative to race tire classes.

    Bottom line: Pax can be a useful tool to compare across classes, especially if you don't have good in-class competition. It's always "wrong" to some degree, but usually not that far off.
     
    john Dameron and riccnick like this.
  4. G72Zed

    G72Zed Veteran Member

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    I would just like to thank you for taking the time to post this valuable information up. Great info JM, thank you.
     
  5. Schubitzky

    Schubitzky Veteran Member

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    Good write-up. I think I remember talking to you at CAM East last year.
     
  6. JMcDonough

    JMcDonough Member

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    Hi Mike,

    Thanks - looking forward to crossing paths and talking 2nd gens at more events in the future. That was both the car's and my debut in CAM-T. Did you run into issues on Day 2? We made it through all the runs, but not without a number of learnings - some of which are relevant for this thread:

    1. Edelbrock Performer Carbs and Autocross don't mix. It fuel starved all over the course on every run. We raised the float level some but that didn't really help much. Granted, that's with 305mm RE-71R's on all 4 corners, but even on corner exit when opening up the steering wheel it would continue to misfire for what felt like an eternity. Going to a Holley carb for subsequent events last year made things much better. EFI is the plan for 2020 (if we have a season).

    2. Before runs in the afternoon on the 1st day, I tried to use a 12v air compressor through the cigarette lighter. This promptly blew a fuse under the dash that took out all the gauges. Apparently a previous owner decided that the 12v outlet and all the gauges only needed 5A fuse. Anyway, the engine still started, so I went ahead and took my runs and found a bit of time over morning runs.
    Key take away: surprises/distractions will happen and you need to be able to focus and drive through them.

    3. We didn't have a front sway bar on the car yet, so we attempted to use front shock adjustment to band-aid the lack of roll control. Wrong tool for the job and the car had a ton of roll, but I'm glad we didn't scrap going to the event because of all the other things we learned. 33/41 in the standings is an ego bruise when you're used to competing for podium spots, but it was a good motivator and you have to get through the teething issues sometime. And it was still a bunch of fun. Met lots of people and had a blast behind the wheel for the first time.
     
  7. Schubitzky

    Schubitzky Veteran Member

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    I was sitting in the trophies after morning runs day 1, but I think we overheated my RE-71s in the afternoon. It felt so greasy and I ended up losing time while others picked up and knocked me out. 2nd day I had a PTFE fuel line break so I co-drove with Sean Rupp in his T/A. I did terrible in that car for some of the reasons you talk about in your article. The seats had very small bolsters, non-locking 3 point belts, way more power than i'm used to, and it had a quadrajet. I couldn't drive that thing smooth to save my life, but it was still a good time. He's made quite a bit of improvements to the car since then. I hope we have a season too. I doubt I go back to Peru this year, but i'll be at Carlisle GM Nats, UMI Challenge, and King of the Mountain. I also wanted to do the DC pro solo, but that got cancelled.
     
  8. 71RS/SS396

    71RS/SS396 Veteran Member

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    The two most common mistakes I see newbies make is over driving the corner entry and not looking ahead.
     
  9. JMcDonough

    JMcDonough Member

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    Good point - Andy Hollis has a nice top 10 mistakes:

    https://forum.miata.net/vb/showthread.php?t=44932

    To your point, #s 9 and 10 from the above link:

     

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