It’s raining lies: part 1

This week I attended a Ross Bentley webinar titled “The Art and Science of Racing in the Rain”. He runs webinars several times per year with a cost somewhere in the $50-100 range. Is it worth it? Yes, I think it is. If you’re serious about racing and improving your lap times, $59 is one of the cheaper expenditures you’ll have. Looking back, I’ve attended a bunch of his webinars: Speed Secrets, Tires, Drive Faster, Reading Your Car, Chalk Talk, and now Rain. That may be all of them. I’ll be the first to admit it, I’m a huge Ross Bentley admirer. But I’m also here to tell you he lies. OK, so that’s maybe too strong a statement. It would be more accurate to say his theory is sometimes incorrect. But this is YSAR and we write provocative shit here, so yeah, Ross Bentley is a goddamn liar.

Before some other Ross Bentley fanboi punches me in the face, let me explain (yes, I said other and I’m a little worried about hitting myself in the face as I write this). I don’t dispute Ross’ advice on driving in the rain. I’m going to do exactly what he says. What exactly did he say? Well, you have attend the webinar for that. I’m not about to pirate his content. But I will reference the parts that need critique.

In the rain, soften the suspension to decrease weight transfer.

— Ross Bentley

Softening the suspension does not decrease weight transfer. The more the vehicle pitches to the side, the more weight is transferred because the center of gravity moves more. One of the attendees wrote the equation for that in the chat box and it stopped all chat for a while. Nobody wrote “Ross, you’re full of shit” because we all respect Ross too much. But let’s be clear, softer means more weight transfer, not less. It is true that in the rain there is less weight transfer compared to dry, but that’s because the corner speeds are lower, not because the suspension is softer. So why, I ask you, should one ever soften the suspension? You’ll have to wait for that answer…

In the rain, lateral grip is affected more than longitudinal grip.

— Ross Bentley

This is not my experience. I find that braking works nearly as well in the wet as the dry. I use pretty much the same braking markers. Now it’s true that my straight speed is slightly lower in the rain, and pick up a later apex, but the grip is still darn good. Don’t take my word for it, or anyone’s word for it. Look at the data. In the image below, the blue line is dry and the black line is wet. The downward slope of the lines in the braking zones are nearly identical. The longitudinal G-forces in the 2nd panel show that peak Gs are similar, as you would expect.

Have you ever stepped on the throttle a little too eagerly in the rain? The car spins around without giving any warning. The grip under braking and accelerating are totally different in the rain. Note that this is from my experience driving high performance street tires not F1 racing tires. Since I’ll bet that you’re racing on tires sort of like mine, I think the difference between braking and accelerating grip is a very important distinction. My experience with corner grip is that it’s not as bad as you might think. The graph above backs that up. If I was going to put some subjective numbers on comparative grip levels in wet vs dry, I’d say braking has 9/10 grip, cornering is 3/4, and accelerating is 1/4. Although Ross didn’t put such numbers on these, he ranks them as braking > accelerating > cornering. So who is right? Turns out we’re both wrong.

Back in 2012, Car and Driver did a really nice comparison of 9 performance tires. For example, on the Bridgestone tire, the skid pad grip was 0.89G in the dry and 0.83G in the wet. That doesn’t sound like a very large change in grip level. They also reported 50-0 mph braking distance as 80 feet dry and 101 feet wet. Putting those distances in terms of Gs, that’s 1.04G dry and 0.83 wet. There are actually two lies we need to debunk here. The first one is that cornering grip is more adversely affected than braking. It isn’t. In terms of Gs, 0.06 is smaller than 0.21 by a metric shitload. To put this in terms that you might appreciate more, you can go 75.7 mph around a 200 ft radius circle at 0.89G. At 0.95G (plus 0.06) you get 78.2 mph. Racers would throw loved ones under a us for a 2.5 mph corner speed advantage. At 1.2G (plus 0.21) speed is 87.9 mph. I don’t think I have the macabre imagination required to describe what a racer would do to get a 12 mph advantage.

WHAT THE FUCK IS GOING ON HERE? This doesn’t mesh at all with my driving experience, the data above, or Ross’ instruction. Corner grip is less affected than braking? It’s true. It’s right there in the numbers. So why do we feel like it is less? And why do the telemetry traces tell a different story? Sorry, but you’ll have to check back next week for those answers.

What’s the other lie? It concerns the friction circle. The way the friction circle is explained, your tires have a certain amount of grip and you can divvy that up between lateral and longitudinal axes. So you could go 50/50 or 90/10 or 100/0. But it’s not symmetric, and therefore not a circle. Tires actually have more grip under braking than cornering. In the example above, 1.04G braking and 0.89 cornering. Circle shmircle. What’s one more drop in a bucket of lies?

Check back if you want to see how this mystery resolves…

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Power, grip, and aero in theory

Six months ago I did some simulator tests where I used Assetto Corsa to answer questions about the relative contributions of power, grip, and drag. I wanted to follow that up a little with something a bit more rigorous. So I took my driving inconsistencies out of the equation and had the AI drive the car. I did a bunch of experiments on a lazy Sunday using the original rFactor. That was fun and informative, but I’m not reporting on that today because I decided to write a program that simulates a car driving around a track. Why? Well, honestly it’s because I wanted to implement the various equations myself. Most of the math is pretty easy in isolation. Equations for acceleration, lift, drag, etc. aren’t too complicated. Putting them together sometimes is though. For example, as you increase speed, you increase drag. So acceleration gets worse the faster you go.

The Model

Track

The track is modeled as a series of alternating straights and corners. The simplest description would look something like this.

S:2000
C:200:60

This means a 2000 foot straight followed by a 200 foot radius corner with a 60 degree arc. You can chain together any number of straights and corners to create whatever track you like. The sections don’t actually need to connect in a closed shape. I decided to use Thunderhill as that’s one of the most popular tracks in the region. I used Google satellite images and scale bar to rough out the track. It comes out as 2.94 miles, which is pretty close to the actual length. Note that my track model doesn’t take into account elevation or camber (yet).

Corners

Under the assumption that the driving line is circular, corner speed depends only on the radius of the corner and the grip of the tires. This is made a little complicated by aero modifications that increase grip and speed by adding downforce, but only a little. Because the corner speed is constant, it’s trivial to determine how much time was spent in the corner.

Straights

Straights are somewhat complex to model because the vehicle increases speed for some time, and then brakes to arrive at the correct speed for the next corner. This calculation depends on initial speed, engine power, gearing, aerodynamic drag, frontal area, and grip of the tires. A simple way of thinking about it is that the total time is the sum of the accelerating time plus the decelerating time. The way I solve it is by binary searching the transition from throttle to brake. At some number of seconds the distance covered and the final speed will be correct: it’s just a matter of making refined guesses.

Vehicle

Since Miata Is Always The Answer, I decided to do experiments with a virtual Miata. People sometimes say “the answer is always Miata” but that would spell out TAIAM, which doesn’t mean shit. Let’s give some parameters on the typical Miata that we will vary to see how the lap times change.

  • 2300 lbs with all fluids including the driver. We’ll strip some weight out of this to see what happens. We’ll also add a little.
  • 100 HP. My model assumes an engine of constant output. I don’t take into account the torque curve or gearing yet. It’s best to imagine “100” as a placeholder for both torque and horsepower, and the value of 100 is not a very healthy example of the breed.
  • 0.40 Coefficient of Drag. A hardtop Miata with windows down has a drag of something like 0.4. But topless it’s worse, and you could always add theme and make it terrible. For reference, a Prius is below 0.3 but it would be hard to get a Miata that low. However, a Prius has a larger frontal area.
  • 0.0 Coefficient of Lift. I abstract the various aero components into a single item rather than wing, splitter, diffuser, etc. A wing can be flat surface made from plywood with a CoL of 0.75  or something wing-shaped with a CoL of 1.0-1.6. The default value is 0.0 but a base Miata probably has some lift.
  • 0.0 sq-ft wing area. I’m not sure how to convert the various aero surfaces into wing area, but 0-12 feet in 4 foot increments seem like a reasonable range. The default value is 0.0.

Results

Power

It’s probably no surprise that more power reduces lap times. This is especially true if you have an anemic engine. Adding 20 HP sees lap times dropping by 3.08 sec. Another 20 HP is 2.57 sec. While there are diminishing returns, there are significant benefits to 200 HP and beyond. What’s amazing about engines is that you can realistically have them vary over a huge range. A turbo or supercharged Miata can make 300 HP. It might not make a good endurance racer at that point. However one of the most successful Lemons cars is the turbocharged Miata from Eyesore racing. In a race situation, high HP is doubly useful because it’s much easier and safer to pass under acceleration than braking or cornering.

Grip

The more corners a track has, the more grip becomes the key factor in performance. On a circular track, grip would be the only factor (assuming you have enough power to drive a given speed). Even a small change in grip can make a large difference in lap time. For example, a change from 1.00g to 1.05g drops lap time by 2.77 seconds. If you look at the telemetry of different drivers in the same car, you’ll see some people can extract more grip than others, and I think this is largely why some drivers are a couple seconds faster than others. In this model, an all season tire is about 0.90 grip. Summer tires 0.95, 200TW 1.0, Semi-slicks 1.1, Slicks 1.2. While these figures may not be correct, it’s the relative difference that’s important. If you want to win, get the grippiest tire allowed by the rules. The UTQG rating is only a rough indicator of the grip. In the crowded 200 treadwear class, I’ll bet there’s more than 0.05g of variation, especially when you consider differences in rim widths and tire pressures.

Aero

There are two components to aerodynamics, drag and lift (three if you count aesthetics). Drag has a relatively mild effect on lap times. Slipstreaming the heck out of it won’t see more than 1 second improvement. Similarly, ruining your CoD to a tune of 0.5 won’t see you slower by more than 1 second. Of course, every second counts, but this is the least useful area to tune. However, cosmetically, not much says racecar more than a wing.

Because lift affects grip, and grip is incredibly important, an aero package that increases downforce has a reasonable effect on lap time. Simply adding a wing could see your lap times dropping by 1.3 seconds (this is the Ideal 4 column below). There is some drag associated with wings, however, and on a track that is more straight than corner, a wing may do more harm than good. Note that a splitter can both decrease drag and increase downforce, so not all downforce increases drag. While you won’t see huge improvements in lap time from aero, it’s a one-time cost, unlike tires, and a well made aero package could see you dropping 1-2 seconds.

Weight

Removing 100 lbs will see lap times dropping by only about 0.6 sec. Weight reduction appears to have a relatively minor effect because it varies over such a restricted range. It’s a lot easier to improve your power:weight ratio by adding horsepower than removing pounds. So weight reduction might not seem like it’s worth doing, but it is. Out in the real world, the relationship between load and grip is sub-linear, so dropping weight is better than the model shows. There are also gains to be had in component longevity and fuel economy. The simple weight loss associated with angle grinders is relatively cheap, but when you start replacing structural parts with lightened versions it gets costly.

Some example builds

Let’s close this out with some example builds and lap times. Note that for a variety of reasons, the absolute lap times aren’t exactly as you would see at the track, but they aren’t very far off. It’s more important to think of the relative differences.

  • First day at the track – untuned engine (120 HP), all season tires (0.90g), open top (0.45 CoD, no downforce), and a coach in the right seat (2500 lbs) = 2:33.20
  • Solo – as above, but with Summer tires (0.95g) and no passenger (2300 lbs) = 2:28:91 (4.29 sec faster than above)
  • Sport build – engine is mildly tuned (130 HP), 200 TW tires (1.0g), hard top (0.40) and enough weight reduction to offset the top = 2:24.25 (4.66 sec faster than above)
  • Budget enduro – 100 lbs of weight reduction (2200), an additional 5 hp (135), DIY splitter and wing (0.35 CoD, 0.75 CoL, 8 sq-ft area) = 2:21.14 (3.11 sec faster than above)
  • TT build – as above, but using stickier, wider tires (1.05g) and professionally designed aero (CoL 1.3) = 2:17.36 (3.78 sec faster than above). Now I’m sure you’re wondering if it’s the tires or aero. It’s mostly tires (2:18.44 vs 2:20.09).
  • Eyesore – a famous Lemons car with a ghetto-charged motor that was dyno’d at 197 hp. It’s light (2200), has 200TW tires (1.0g), and theme for aero (0.45) = 2:17.29.

At some point I need to put this theory through some real life testing. I honestly can’t imagine anything more fun than going to a track day with 4 sets of tires, removable aero, and some ballast. It would be a long, hard day of work, but what a day. It costs $2200 to rent Thunderhill West for a 2-car test day. In the off-season, they sometimes cut that in half. I just need to find another car to share the session with and a crew to help out with the pit work.

The 8 stages of driver development

Novices seek power. Intermediates seek grip. Experts seek balance.

— Ian Korf

Yes, I just quoted myself. Well, if a blog is anything, it’s self-serving. Let’s talk in more detail about the typical progression from driving the engine to driving the suspension. But not without first taking a detour into tennis.

The following photo comes from a blog on Learning the Different Types of Serve. People who know tennis will laugh at this photo pretty quickly. Not only are the players in the receiving court in the wrong position, but the guy has absolutely no idea how to hold a racquet. This is as bad as the Thrashin’ poster a few weeks ago with the dude’s wrist guards on backwards.

Serving is a complex motion that takes a long time to learn how to hit properly. In the beginning, players use a forehand grip (like the photo above), swing in a circular arc from head to toe, and possibly use a wrist snap in an effort to get more power. At the end of the stroke, their racquet is pointed at the ground. If they follow through, they are in danger of hitting their shins. Examine the next photograph, which shows the follow through of a proper serve. What do you notice?

The racquet is in front of the body, nowhere near the shins. The elbow is nearly as high as the shoulder. A proper tennis serve starts by holding the racquet in a backhand grip. The racquet is swung up and out, not circularly down. The follow through sees the arm pronating as it extends. That might look like a wrist snap, but it’s a rotation at the elbow. The palm ends up facing away from the body, not down at the ground. It’s a complicated motion that feels unnatural to novice players.

Track driving also features some unnatural feelings in the beginning. But over time they start to feel ok, then good, then just how it’s done. Let’s talk about the typical stages a driver goes through. Well, in my experience anyway. It’s not always the same order, and there are probably some other steps along the way and afterward. I’d be interested in hearing opinions on that.

Stage 1: Speed Focused

People who don’t know shit about track driving are generally concerned with the performance of the engine. When random people hear you drive a car on a race track, what’s the first thing they ask you? “How fast do you go?” Driving fast in a straight line is sort of thrilling for a little while, and many of the novice students I see come and go with that in mind. Part of the interest in going fast is to experience the awesome engineering in sports cars today. Well, there’s even more to appreciate in how well they do the twisty bits.

Stage 2: Exit Focused

In the next stage, drivers know the racing line, but they take the phrase in slow out fast a little too seriously. They slow down to a crawl, tip-toe through the corner, and floor it at the exit. They think that because they went in slow and out fast that they cornered correctly. These drivers may exhibit heel-toe shifting, because they want to be in the correct gear, since they’re still concerned with maximizing power. But the technique is often lacking and they press the clutch in way too early and let the revs fall. It’s also typical at this stage to drive a mostly circular arc through the corner. This leaves the car mid track at the exit and then the driver steers out to the apron because their coach told them they were supposed to use the whole track. Most of the drivers I work with in the Hooked on Driving Novice group are at this stage.

Stage 3: Brake Focused

As drivers become more confident, they stop coasting into braking zones and learn to threshold brake. These drivers exhibit a point-n-shoot driving style where they drive hard all the way to the braking point, hit the brakes hard, corner mildly, and then hit the throttle hard. It’s a fun time blasting your car in and out of corners, even if you don’t do it optimally. And high performance cars can get around a track pretty quickly like this. Lots of HPDE regulars settle into this style of driving. When their lap time stagnate, they buy a faster car. Too bad, because they would improve more by learning how to drive a momentum line with a slower car.

Stage 4: Hooligan

Some, but not all drivers, go through a hooligan phase where they have become enamored with burning rubber. Let’s face it, drifting looks cool and feels amazing. Although it’s not the fastest way around the track, it’s fun and requires some skill with the throttle pedal. What the hooligans misunderstand is that rotation in the corner isn’t supposed to be initiated with the throttle. I don’t get to see many hooligans as students. I had one, who broke the mold a bit as she was a 60 year-old lady. While she smoked the hell out of her tires in the figure 8 drill, she was clumsy and slow on track.

Stage 5: Grip Focused

The next phase is characterized by mid-corner tire squeal. Grip junkies can drive a car pretty damn hard. They aren’t necessarily consistent, especially at setting their corner entry speed. But their fast laps are truly fast. These drivers tend to open up their steering in the second half of the corner to maximize their traction. Some may be very good at countersteering. Although rare, I like working with these students because they are confident in their car control skills, just not refined. Sometimes it takes just a few words to get them changing their driving style for the better. I think a lot of HPDE coaches are at this stage.

Stage 6: Entry Focused

Trail-braking is such an essential skill that I teach it very early. As in the first day. Hard on, soft off keeps the car settled. But advanced trail-braking is a really different skill whose goal is to optimize the corner entry by (a) setting the ideal speed (b) setting the ideal angle.

Every corner has an optimal speed. If you enter too fast or too slow, the exit will be ruined in one way or another. So one of the primary goals of the advanced driver is arriving at the nadir (the point of lowest speed) at precisely the correct speed. Trail-braking helps you sense your speed because the self-centering torque of the steering wheel gives you critical tactile feedback.

Every corner also has an optimal angle, and it’s farther down the track than most people expect. Getting the car rotated early requires oversteer and therefore requires countersteering. But just because you’re countersteering doesn’t mean you’re cornering properly. Hooligans can be pretty good at countersteering but they do it under acceleration. Trail-braking requires countersteering while braking.

Stage 7: Balance Focused

The next stage of development sees drivers trying to optimize traction everywhere on track. Everything is a compromise and identifying the optimal inputs is a continual experiment as the car, track, and environment change. Balanced-focused drivers are concerned with making every transition, be it speed, direction, or gear, as smooth as possible. So they are tuned into their suspension to optimize their contact patches. They drive the capabilities of the car, they don’t ask the car to drive to their ability.

Why is smooth so important? In mathematical terms, it’s because tire load is sub-linear with grip. In seat-of-the-pants terms, you can’t get back traction you lost. Paradoxically, some very smooth drivers don’t look smooth from the cockpit. Don’t watch their hands, watch the attitude of the vehicle. Is the suspension quiet or is it rocking?

Stage 8: Unfocused

Some drivers are so damn good that they don’t even think about driving. Their minds are capable of completely independent thought while driving a car at the limit. If they’re technically-minded, they’re analyzing the behavior of the car to improve it later. If they’re competition-minded they’re figuring out the strengths and weaknesses of the drivers around them. If they’re assholes, they’re messing with their opponents’ heads. (That was Ravenclaw, Gryffindor, and Slytherin by the way. Hufflepuff is still in the pits helping some poor dude fix a throttle cable).

Balance takes time

I have a balance board in my office. So does Ross Bentley by the way. I love Ross and everything he teaches, but I wasn’t shamelessly copying him when I got it. I only found out later he also has the exact same one. Racing is a kind of balancing act. You’re trying to maximize your contact patches through changes in speed, camber, temperature, surface conditions, etc. But that’s not really the reason to use a balance board. They are really different activities and I don’t think there’s much cross-over. The reason to use one is that it improves the motor skills of the foot, which is pretty important for throttle and brake control. It also increases core fitness, which is important for just about everything.

I have neglected core fitness for a long time. I’ve done a lot of exercises, like sit-ups, really incorrectly. 50-ish years of ignoring my back recently put me in a bad way. My back pain was so terrible that I could barely walk, sleep, or do anything at all. So I took a lot of ibuprofen. Too much actually. It did allow me to drive at NYST and Pineview, but I ended up skipping Shannonville the next day as I felt terrible. I say too much ibuprofen because I stepped on a scale and found that I had gained 14 pounds in 9 days. Sudden weight gain can be a sign of kidney failure. I went to the ER and they said to lay off the ibuprofen. I lost the weight over the course of the next week and I’m not sure I’ll ever take pain meds again. X-rays show some arthritis and disk degeneration. So I’m now trying to become educated in back health as one of my highest life-long goals.

Back to balance. The first time my graduate student Hannah tried using my balance board, she could not stay on it for more than a second. Undaunted, she kept at it, but never really improved. Maybe 1 week later she tried again, and suddenly she could do it for a few seconds. She did absolutely no training in between. A few weeks later, she steps on again, and this time she can drink tea while balancing. The last time she tried it, she could have a whole conversation while balancing. In the picture below, she’s experimenting with different ways of standing on the board (here, a bit more of a surfing style).

How did she get so much better without ever practicing? Time. It takes time for your body to learn new activities. How much time? I don’t know, but I would guess a few sleep cycles is important. I think it would be better to do two track days 1 week apart than do 3 track days in a row. I don’t think this kind of learning without trying works very well at the intermediate or advanced levels. You really need a disciplined training schedule at some point or your skills will plateau and eventually degrade over time. But if you’re just starting out, don’t overload yourself. There’s only so much you can learn in one day.

Wait, isn’t this a blog about driving? I had better say something about that!

  1. Novices seek power
  2. Intermediates seek grip
  3. Experts seek balance

There’s a reason for this progression. When you’re starting out, not only do you not know what balance is in the context of driving a car, but there are only tenths of seconds to be gained in optimizing how you interact with your suspension while there are multiple seconds elsewhere. As the title says, balance takes time. It also happens to make time. More on that next week.

Track Review: Pineview Run

Have you ever been to an executive or par 3 golf course? With typical distances 100-200 yards, there’s more swinging and less walking per minute. To me, that also means both more fun and more practice per minute. The strange thing is, there aren’t that many short courses. For some reason, people like full size courses. It can’t be because they like walking, as most people use golf carts. It can’t be because they like hitting their long clubs, because nobody says their favorite club is their #1 wood. It can’t be because they’re working on their game, because if they wanted to do that, they’d be on the driving range or putting green. I guess it’s because real golfers play on real golf courses. However, if you want to get better at golf, you’re better off working on your short game. And this is true in the car world too.

Pineview Run is the executive/par 3 of road courses. It’s short, twisty, and low speed. Perfect for working on your short game, if you will. You spend most of the time in 2nd gear, a little in 3rd, and none in 4th. It’s ridiculously fun to throw you car around this twisty ribbon of asphalt. Some people might describe it as a hilly autocross. Others might say it’s a kart track. There’s some truth to both these statements. It’s really tight and not that wide. But that doesn’t diminish its appeal to me or it’s utility as a training tool. Ultimately, it’s a driver’s track. It’s where you go to hone your muscle memory. The low speed makes it safer and less intimidating for the novice, and its technical nature makes it an ideal practice ground for more experienced drivers.

In order to get access to the track, you have to become a member, which means plunking down a sizable chunk of change (minimally $2500) for several years (minimally 5). After that, the track time is quite reasonable and works out to something like $100 per track day. I think that’s a smashing deal considering how much one could improve their driving there. I worry a little that the clientele Pineview is courting isn’t going to sign up. The kinds of people with the money for a country club membership drive Porsche 911s, not Miatas and 86s. The 911 crowd wants to let their dog hunt, and that just doesn’t happen on a 2nd gear track. People with cars capable of 150 mph don’t want to drive a track where their top speed is less than the highway they arrived on. I see this attitude all the time at my favorite track: Thunderhill West. People complain that it’s too twisty, too blind, too off camber… too much work. Most track organizations host events on the East (3 mile) track instead. I want to ask them, “do you even like driving?” Then I remind myself that apparently drag racing is a thing.

The problem is that Pineview is even slower and more twisty than Thunderhill West. Who wants to drive their sports car on a kart track? Well, besides me. Autocrossers, that’s who. Pineview is the middle ground between a parking lot with cones and Watkins Glen (a famous high speed track located about an hour away). However, the autocrossers spend even less money on track time than the HPDE crowd and are unlikely to purchase memberships.

So Pineview finds themselves in the difficult situation of having a business model that doesn’t fit with their track. How will this work out? Well, hopefully, people wake the hell up and realize that twisty driving is fun driving. I don’t see that happening. Hopefully Pineview opens up some public days and partners with some local autocross clubs.

Here’s what the track looks like from inside my brother’s Miata. Sorry about the sound. Even on low setting the wind noise sounds like someone ripping on a bong (not my phraseology). First 3 laps are me. Second 3 laps are Mario.

P.S. The APEX Pro is kind of fun to watch don’t you think?

Product Review: APEX Pro

TL;DR: Buggy software and difficult to use but with a simple change could replace RumbleStrip as the best delta timer.

Beautifully Designed

If you saw the video in the post last week, there was a curious device with blue and red LEDs on the dash. That’s an APEX Pro, and it’s one of the most interesting driving devices in recent history. The hardware itself is gorgeous. It’s a block of metal the size of a pack of gum with one button, one USB port, and 12 LEDs. It feels great in the hand and looks better in the car. There is a separate base that attaches to the car with an adhesive and the APEX Pro magnetically locks in place very securely. The internal battery lasts a couple hours, but you can also plug it in if you’re running endurance races, for example. The physical design is really appealing and I wouldn’t change a thing.

Apex-Pro-Digitalcoach

Phone Required, Desktop Supported

The APEX Pro requires a phone. That’s how you tell it what track you’re on. It has a huge track library but you can also define your own track. The phone software is pretty slick. It lets you export data, see who’s using the device at the moment, and let’s the team examine your laps from the inconvenience of their phones. I say inconvenient because looking at squiggly lines on a phone is tedious. The better way to review APEX Pro data is with a desktop app where you have a large monitor and a mouse. Although APEX Pro doesn’t come with its own desktop software, it imports into the Track Attack desktop app really easily, and Track Attack is pretty good.

Data Logger

As a data logger, it works well. It has high resolution GPS and a bunch of accelerometers. Other similar products include the AiM Solo and several phone-based apps like Harry’s Lap Timer, CMS Pro, Track Addict, and Track Attack. At $450, the APEX Pro is $50 more than an AiM Solo. But once you figure in a secure mount for the Solo, it’s not much different. The biggest difference is the display, which I’ll get to later. As a data logger, there’s not much difference between the two devices. But why fork over $400+ when you get the same functionality out of a $10 smartphone app? Because smartphones have lower quality sensors. If you decide to use your phone, you’ll need a very secure mount and a high resolution GPS antenna. This will set you back around $150. That’s a lot cheaper than an APEX Pro or AiM Solo and the quality will be acceptable. I prefer dedicated devices to phone apps, but I’ve also had good experiences with phones.

Apex Score

The sine qua non of the APEX Pro is its Apex Score. The brain of the device learns both you and the track while you drive it. After a couple laps it can tell you where you’re driving under the limit. The idea is that it’s like live coaching. A quick check of the LEDs tell you your current Apex Score. What exactly is Apex Score? Some combination of speed, G-forces, and yaw I suspect. Under the hood, the APEX Pro is doing some machine learning magic. Unfortunately, that magic is full of bugs. You can observe these bugs really easily. Just load up a couple of laps and overlay them. Turn on all the sensors so you can see their raw outputs. If you’ve been driving consistently, you’ll see consistent sensor values. But the Apex Score will be all over the place. Whole sectors of the track will differ in Apex Score from one lap to the next. It makes no fucking sense.

For racers who are driving close to the limit, the Apex Score is not something you’re trying to optimize. If two drivers have the same lap time, the one with the lower Apex Score is the one doing less work. They’re driving more efficiently, which pays off the longer the race goes. So novices will be interested in maximizing their Apex Score while racers will be trying to minimize it. That’s sort of confusing.

LED Display

The LED display is really cool. You can adjust the colors and brightness. Apart from looking totally amazing, it’s completely useless. The idea is that you can check your Apex Score at any time. But the only time it’s really safe to look at it is when you’re on a straight. You simply cannot look at it mid-corner. I’m a pretty advanced driver, and I had a hard time watching the thing. A novice who is struggling with finding the limit is going to be a hazard on track if he’s also trying to monitor his progress by watching LEDs.

So what happens when you look at it on a straight? It shows 4 green and 4 red lights. Let’s talk about what the lights mean. If there are 8 red lights, it means the total grip available is 8. As your performance increases, green lights will overwrite the red lights and you might see 6 greens. There are still 2 more greens to go if you push it harder. So what does 4 green 4 red mean on a straight? That I’m not pushing hard enough? Uh, the pedal is all the way on the floor. I literally can’t go any faster yet the Apex Pro thinks I can. But if I crest a hill and the car gets light (e.g. T7 at NYST last week) then all the lights go green because somehow the change in vertical acceleration indicates I’m at the limit. Bonkers.

Let’s sum up.

  • When you can look at the Apex Score (straights), it gives the wrong answer.
  • When you want to look at the Apex Score (corners) it’s not safe to do so, and if you did, the Apex Score might be wrong anyway due to software bugs.

Ultimate Lap Timer?

Data loggers are essential for reviewing your performance after the session. While you’re in the car, the most important tool is the delta timer, which lets you perform and analyze driving experiments every corner. It works like this: “I wonder if staying in 4th will be better than downshifting to 3rd?” Check timer before corner. Drive the corner. Check timer after the corner. “Hey, I dropped 2 tenths, that was better”. Note that I didn’t try to check the timer mid-corner. That’s dangerous. My favorite delta timer is the RumbleStrip DLT1-GPS. Why? Because of the big red LEDs. You see them instantaneously even on a sunny day. It’s so much easier to see than an LCD from a phone, tablet, or AiM Solo. You might think $300 is too much for something that doesn’t even log data. But it’s the best $300 I’ve spent on racing.

My RumbleStrip is such an important part of my driving that I literally feel naked without it. If you do a lot of sim racing, you probably feel the same way about your on-screen timer. iRacing has a particularly beautiful delta bar that shows how far off you are from your best lap and if you’re gaining or losing. It’s just a red/green bar on the screen, but it’s incredibly effective. The APEX Pro could be configured similarly with its LED strip. I understand that the underlying motivation behind the APEX Pro is the Apex Score. While that may be a useful tool for coaching novices and intermediates, it’s not what advanced drivers want. Give us the option of a race mode where the LEDs display a time delta. Give us the sexiest damn lap timer on the planet. And unlike my RumbleStrip, I’d get to review the data after the session. Yeah, that would make the APEX Pro worth every penny.

Track Review: New York Safety Track

The original plan for the weekend was to race my brother Mario’s Miata at Calabogie in the AER series but the car wasn’t ready so we made alternate plans and took his street Miata on an HPDE safari. While racing is always a great rush, the first few laps at a new track are such a special experience that I didn’t mind the change in plans. The first track we hit was New York Safety Track (NYST). NYST is a relatively unknown track that caters more to motorcycles than cars. It’s a family run business that’s been open for only a few years. It looks great on paper/video so I was eager to check it out.

My normal preparation for driving a new track is to run a bunch of laps on a simulator. Laser scanned tracks are accurate to the centimeter, so you have a pretty good idea of how to drive the track when you get there. But real life is always a little different than virtual. You perceive elevation changes much more in person, for example. But there are other, more subtle differences that add up to a unique ‘feel’ in the real world that can’t be duplicated in simulation.

Unfortunately, NYST doesn’t exist in the simulator world, so I couldn’t prepare that way. So I did my homework by watching youtube videos, marking up track maps, and imagining myself driving the track. There’s a saying that no battle plan survives contact with the enemy. It’s sort of like that with track preparation. What may seem like an ideal line on paper can be suboptimal in real life. So whenever I go to a new track, my main goal is to explore the space a little. As a result, I overdrive the car a little rather than trying to optimize lap times.

Here’s what I wrote ahead of time about NYST. In red are comments I made afterward. Video follows text.

T1-T2: The T1-T2 combo is taken as an increasing radius turn with a lot of slowing early and then full throttle as soon as possible. The main straight climbs gradually into the braking zone. The apex is right at the peak of the hill, at which point the track turns down and opens. It’s important to get on the throttle early and use the whole track while unwinding the steering.

The braking point is ludicrously deep. You can brake at the 100 marker and then flick it over the hill.

T3: Double-apex carousel that is half descending and half ascending. Set up wide at the entrance, brake through the first apex, maintain throttle through middle, and gas it out to the exit, but be careful because there is no exit apron (here or anywhere).

As expected, the exit pinches in, so you want to let the car drift left a bit before hitting the second apex.

T4-T5: Flat out. T4 and T5 are slight bends right and then left, but the racing line is straight through. The apex of T5 is slightly blind.

T6: Another descending-ascending double-apex carousel. Unlike T3, the apexes are really far apart and the track-out is held tight to set up for T7.

I liked this as a double apex rather than holding a tight line. I feel like the exit speed is better. Too bad I didn’t have my RumbleStrip with me to test.

T7: Flat out. T7 is a blind right-handed bend that should require no turning if the exit of T6 is held correctly.

This turn feels a little like Buttonwillow Phil Hill. Turn it in before the hill and just go straight over.

T8: This is the highest speed corner of the track. Set up track right on entrance and stay mid-track at the exit to get ready for the esses ahead.

T9-T11: Rolling esses. As soon as you pass the apex of T8, get the car straight and unloaded. The braking zone to T9 is short. Brake just a touch into the hill. T9 is a blind right-hander that is quickly followed by T10 (left) and T11 (right). Like any esses, sacrifice the exits, except for the last one. Track all the way out of T11.

There are two ways to handle this complex. You can shift down to 3rd before or after 9. My guess is staying in the high gear is better because downshifts often end up with too much braking. But downshifting before gives you a great run up to 11.

T12: Descending decreasing radius 120. The track will start to descend before the braking zone to T12. It’s tighter and longer than it looks and continues downward. Get rid of speed early since it’s dangerous to do so mid-corner. Stay tight the whole way around.

The corner is so damn long that it’s possible to brake through some of the corner. It is off-camber, so you don’t want to run too wide. This was a surprisingly fun corner.

T13-T14: Long left. One might think of this pair as a single decreasing radius turn, but the exit of 14 is kinked, so there’s no point in holding out for a fast exit. Just go around on the inside and manage traction. It’s possible a double apex line is best.

The geometry of the turn invites oversteer, which you can see in the video.

T15: Sharp 90. This sets up the climbing section, so the exit is important, especially in a momentum car. The entrance is kinked. Should one try to get all the way track right, which requires additional braking, or does one enter mid-track at higher speed? In either case, running out of room at the exit will hurt because there is no apron.

It’s a slow rotation corner, so optimize the angle by getting as far right as possible before the turn.

T16: Flat out. T15 is so slow that the slight right bend at T16 is not much of a turn. Run over the berm here and the next turn.

T17: Uphill. This is the steepest part of the track. Maintain as much speed as possible with an early apex and fight to keep all the momentum and traction as you continue up. Use as much track as you can.

T18: Cresting left. The braking zone is before the crest of the hill, as is the apex. It doesn’t start to flatten out until the exit. Exit speed is crucial since the main straight follows. So the apex must be late enough that you don’t have to cut throttle if you start heading into the grass on the exit. The apex berm and blind nature of the corner conspire to make you want to take an early apex, but wait on it.

Indeed, the corner invites an early apex, but be disciplined and wait for it.

NYST is a fantastic track. I’m ranking it as my 3rd favorite track behind Thunderhill West and Sonoma. Despite the ‘Safety’ in it’s name, I don’t think NYST is especially safe. Some of the trees are a little to close to the track. Also, the motorcycles drive way too fast in the paddock.

OMG, I tilt my head so much when driving. I’ve got some homework to do there.