Dropping 20 seconds in a day

Last week the student I was coaching at Thunderhill dropped 20 seconds off his personal best in one day. I thought it would be fun to investigate how that happened from the perspective of the coach and the student. The statements in blue are from the student.

The student had some previous autocross experience and had been to a Thunderhill track day once before. So he wasn’t a complete novice. The car was more commuter than track weapon. It was quite comfy with heated seats, adjustable bolsters, and nearly silent exhaust. Here’s his description.

2009 E90 328i 6 speed manual with sport package. No modifications except stainless steel brake lines installed by previous owner. Street brake pads and PSS tires (the tires help me to drop 5 seconds). I replaced engine mounts before 2nd track day. (use OEM mounts).

At the start of the day, I asked him what he felt he was good at and what he needed work on. He said his driving line was pretty good but that he should shift to 4th gear sometimes. As it turns out with rookies, perspectives can be misaligned. His driving line wasn’t very good and there was nothing wrong with not using 4th gear. We kept up with the fastest cars in our group using 3rd gear only. But we’re getting ahead of ourselves here…

Once we got in the car and took a few laps, I could see that, in fact, he does not shift. There are two places on the track where one can downshift to 2nd and three or four where one could get to 4th gear. I made no attempt to fix this. Driving is difficult enough without shifting. I wish all my students would drive 3rd gear only. Less power in corners means you have to learn to drive a momentum line. And less speed on the straights is less wear on the car. I’d also much rather top out at 90 mph than 120 mph in a car I’m not driving. Another thing that didn’t need fixing was his hand positions. He anchored them at 9 and 3 and I never saw them come off. Excellent. I did remind him a few times to relax his grip a little. Thankfully, the most important thing, situational awareness, also needed no fixing. He knew where the cars were around him at all times.

So what did need fixing?

• Braking was early, excessive, and abrupt
• Lack of confidence in grip
• Driving line was circular

The first thing we worked on was trail-braking. What? Isn’t that an advanced driving skill? What am I doing teaching this first? What about the line? FUCK THE LINE. The most important thing you can learn about track driving is how to apply the brake. Hard on, soft off. No, we didn’t work on rotating the car with the brakes. We simply changed the brake pattern from hard on, snap off, to hard on, soft off. This is how one creates smoothness on corner entry, and it’s the foundation for rotating the car with trail-braking (later).

The next thing we worked on was speed sensing. The reason he was braking so hard was that he had no idea how fast one could go into the corner. Self-preservation instincts aren’t bad you know. They keep you safe. But they can also get in your way. One reason to get coaching is to lean on the coach’s experience to increase your limits. He just needed someone to let him know it was safe. The drill we did may seem unusual. I told him he wasn’t allowed to use the brakes at all. He had to plan the corner far enough in advance so that he arrived there with the right speed. Without the brake pedal getting in the way, he drove the entries much faster. With each corner he gained confidence and was eventually going into T2 (a long carousel) at high speed with just a lift, letting his tires scrub off the excess speed.

Lots of people unknowingly drive a circular arc. How can you tell? If the wheel stays at the same position throughout the corner, it’s circular. Some corners can be done that way, but most benefit from a late apex line where the radius of the first half of the corner is much tighter than the second half. And by the way, the halfway point isn’t the apex. The apex is in the second half of the corner. I call the halfway point the nadir. Ross Bentley calls it the EOB (end of braking). In any case, the point where you start to increase the radius is before the apex.

We spent most of the day working on corner entries. As a result, my student’s entry and mid-corner speeds were so much higher than the others in the group that we kept up or passed many faster cars (M2, M3, M4, 911, Lambo) despite not shifting gears. Nobody went faster in T2 despite having stickier tires and aero. And I guaranty our T8 speed was 10 mph faster than anyone else. After the event I emailed the student to find out how he dropped 20 seconds. Blue text is him. Red text is additional editorial comments.

Q: What was the most challenging thing? Physically became tired after 6 sessions. All that sensory input is exhausting. But you get used to it and driving becomes less taxing.

Q: What was the scariest thing? Saw someone rolled his car on track. This was in the last session of the day. Wisely, my student said he wanted to have a less intense final session.

Q: Was there an ‘aha’ moment or was it very gradual? I think it was very gradual for me. Ian is a good instructor who can explain things clearly. Communication is a 2-way street, and not every student-coach pairing is ideal. We were both mathematically inclined, so we communicated like engineers.

Q: Where do you feel you made the most improvements? On to throttle earlier and understeering out of turns. To get on throttle earlier is not so simple. He had to change his whole approach to cornering to make that happen. his use of understeering isn’t quite right. What he’s doing is adding throttle at the traction limit. This means the radius of the turn increases to compensate. It’s a very mild form of understeer.

Q: What would you tell someone who was going to the track for the first or second time? You may not need to drive a powerful car on to the track at the beginning. A well maintained car can give you as much fun as a Lambo or M3. 

Here are a few things that I learned from Ian:

1. No braking approach. At second run session, Ian asked me to run a lap without braking.or minimum braking. It helps me a lot but how? I don’t know how to describe it.
2. My line late apex, early apex, circle arc line. It turned out that some of my lines are just pure circle arc line. My steering input stays same through out my turn.
3. Gas out approach/understeering. I finally realized that how to use throttle to exit a turn. I will try to use this approach at my next autocross event. I alway thought that understeering is NO good until my 2nd track day.
4. Learn road/surface condition. It applies to rally racing a lot. At T3, T5, T9, pay attentions to elevation change and bank angle.

Here are a few turn-specific notes he made, some of which are pretty perceptive.

• During my first track day, I wasn’t sure how fast I could enter T1. To be on safe side, I always braked too early during my first track day. I thought my line was fine but during my second track day, I have learned that my line was actually a smooth circle instead of late apex. At the very last session of my second track day, I began to realize that I could accelerate a lot earlier or during my T1 entry point. In this way, with lots of throttle, my 328i could naturally move to right side of the T1 exit. (using natural understeering)
• T2 is relatively straightforward. I became more comfortable at higher speed to go around T2 at my second track day. In the afternoon session, I started to appreciate the power out approach to exit the turn. Again, using natural understeering of the car. From the entry point to the half of the turn, I gradually added more throttle to almost full throttle. I feel that my newly installed pilot super sport tires have more grip than my old RE050 run flat tires. That is another reason I could run faster at T2 at 65mph(2nd track day) vs 47mph(1st track day).
• At my second track day, I started to realize that there is a slight up ramp at the entry of T3. So my get off brake point is at the crest of the ramp right before entry of T3. My entry line is too tight to the right. I could have move to the left in one car width to have a diagonal entry point. This line seems to be better. Compared to my first track day, my speed at turn 3 is 56mph vs 50mph(1st track day)
• At 2nd track day, my car has gained more speed at T5. My initial braking point was at the top of the hill which makes my car slide a bit. At faster speed, Ian got scared and told me to brake early during uphill ramp and turn in earlier. It makes more sense because braking at uphill gives more traction to turn in.
• At my second track day afternoon session, I felt more comfortable to brake late at T9. I think we could use the uphill ramp to slow down the car and turn in without losing traction. After the crest, it seems that other more powerful cars can accelerate towards T10 a lot faster than my 328i. This is one of the two places at Thunderhill east that powerful cars can make more difference in my opinion. The other one is the straight finish line.
• At T10, I tried to trail braking. I used to brake late and turn in. After discussion with Ian, it seems that I could initiate the turn earlier and carry more speed. However, there were couple of times that my car became too close to the track edge during T10 exiting.
• T14-15 seems to be my worst corner. I feel that I could carry more speed at T14. At the end of 2nd track day, I could accelerate earlier before T15. This helps me to reach higher speed at finish line. At my first track day, I slowed down too much. I had to accelerate my car from lower speed at straight line.

Oh yeah, about that car that rolled. It was a brand-new (2018) BMW. The driver had purchased HPDE insurance for the day. Yes, it sucks to wreck a car, but it would suck a lot more if you didn’t have insurance. If you’re taking an expensive car to the track, please get HPDE insurance. It costs about the same as a track day. Driver was fine btw.