"Mr. Toad" at Thunderhill West (17 July 2021)"Mr. Toad" at Thunderhill West (17 July 2021)
 Checkered flag at Turn 9W |
 A bath eliminated valley dust so the number meatballs wouldn't scratch the finish |
 Mr. Toad and Ray's Miata ready for the day |
 Brake spares: pads and fluid |
 I bumped up to the advanced group |
 My student Steven and his Crossfire |
 Mr. Toad and Ray's Miata panting after a hard workout |
My previous experience with this track was highly abridged for multiple reasons (three strikes, I'm out) during which I was far behind two friends with a MINI Cooper S and a Ford Shelby Mustang GT350. Last November I had another shot at most of the track as part of a Thunderhill 5-Mile day and learned how to tackle part of it, but I was still unsure.
This time, with confidence from Laguna Seca in March (during which I passed nearly every other car on the track), I offered to bump up from the intermediate group to the advanced group. I also was accepted as a coach for a beginner track driver, and coaching another driver added perspective which helped my own driving.
Since installing a StopTech Big Brake Kit (BBK) I had become accustomed to improved lap times. I shaved off nearly two seconds during my second visit to at The Streets of Willow Springs (the first with the BBK), then knocked off 4.445 seconds at Laguna Seca in March. That was my 14th day at Laguna Seca so a 3.8% improvement was significant.
Thunderhill West offered more gain from experience but litle from brakes so my hopes were modest. Slicing just over one second off my lap time in the first, warmup session, was encouraging. During the second session, with the added weight and distraction of a passenger (the beginner driver whom I was coaching), I trimmed another four seconds. By the end of the day, I had chopped 9.116 seconds off my lap time, a nearly 9% improvement. One of my Miata-driving friends, who had expeced to beat me but came up over four seconds short, greeted this news with a rather rude gesture. (We are still friends.)
 A good start (1:41.239) |
 Session 2 with a passenger (1:36.609) |
 Best lap of the day (1:33.132) |
During the very first session, my best lap time was 1:41.239, over one second better than my best lap last year (1:42.248). That was certainly a good start to the day!
During the second session I had the added weight of a passenger, yet still managed to shave 4.6 seconds off my time from the first session. The third session was only slightly slower and then I steadily improved as the day progressed:
Session Best Lap Improvement Vs. June 2020 1 1:41.239 - 1.009 2 1:36.609 4.630 5.639 (with passenger) 3 1:36.791 4.448 5.457 (with passenger) 4 1:34.836 6.403 7.412 (with passenger) 5 1:34.313 6.926 7.935 6 1:33.941 7.298 8.307 7 1:33.132 8.107 9.116
Given the steady improvement through the course of the day, "more experience" appears to be the biggest factor. Practice!
Track Addict breaks a track into multiple sectors, six in the case of Thunderhill West. Within a session it picks the best time for each sector to calculate a theoretical best lap time. For session 7, which included my best lap of the day (lap 4), immediately followed by my second-best lap (lap 5, which was only 0.045 seconds slower), here is what it calculated:
Sector Where Lap 4 Lap 5 Best Time Lap 1 Start - Turn 1W 11.183 11.394 11.004 7 2 Turn 2W - straight 12.804 13.090 12.804 4 3 Turn 3W - Turn 4W 15.159 14.430 14.430 5 4 Turn 5W - Turn 6W 17.633 17.886 17.633 4 5 Turn 7W 10.969 11.001 10.922 2 6 Turn 8W - Finish 25.384 25.376 25.376 5 1:33.132 1:33.177 1:32.169
This analysis is simplistic because sectors are not independent—it can be beneficial to sacrifice speed in one part of a track to gain an advantage in another part—but it's still useful information. The theoretical 1:32.169 would beat last year by over ten seconds. Wow.
Lap 5 was slower from Start/Finish because I passed a BMW which had me slightly off the line for turn 1W, which probably set me up to be a little slower through turn 2W. Without the pass, lap 5 might have been my best.
It's worth further study to see how other sectors flowed to see if they could be combined into a lap close to the theoretical best.
After upgrading to an iPhone 12 mini I found that GPS data had gone to hell. To make up for Apple's failures, I bought a Dual XGPS160 GPS receiver, but at Buttonwillow I found that the device's latest firmware was incompatible with Track Addict. The app's 4.7.0 version fixed that and the collected data appeared to be accurate.
With the Golden Gate Lotus Club I usually run in the intermediate group. Although I have enough experience (multiple times over) to qualify for the advanced group, I've found that many participants have wicked fast cars (often expensive cars) and know how to use them. Curiously, this seems to be less true with the car-crazy SoCal crowd.
My experience at Laguna Seca in March,
in which I passed every other car on the track during the morning and was only
passed by two cars during the afternoon, encouraged me to consider a step up.
When GGLC
emailed that they were short of enough participants to break even
but that the intermediate group was full I offered to move up to the advanced
group, an offer which was quickly accepted. I passed a few cars but most
passed me. That's a welcome challenge.
In addition to bumping up to the advanced group,
GGLC
was seeking coaches for first-time track drivers. I've done that a few
times in the distant past so I volunteered. I was paired with Steven,
who drove a Chrysler Crossfire. It was his first time driving
on a racetrack and he was rough at first—as I surely was—but
despite "drinking from a fire hose" he quickly improved. I not only enjoyed
sharing one of my passions but learned in the process of coaching.
Notably absent from these notes are brake issues. The brakes just worked. Looking back to my brake analysis for Laguna Seca, even the stock brakes were able to dissipate about 1,480 kilojoules. Looking at my best lap, the critical braking was slowing from 85.4 mph to 32.2 mph for Turn 7W, an energy dissipation of only about 990 kilojoules. Even the stock brakes could handle that; the BBK didn't even have to work hard.
In February, prior to going to The Streets of Willow Springs, I upgraded from Nitto NT05 tires, in the stock 225/40R-18 size, to wider (235) Nitto NT01 tires. It was immediately apparent that these 100TW tires were much stickier, and they proved to handle excess tire pressure more gracefully. (I routinely see a 10-PSI increase in front-tire pressures during a track session so even starting from minimal tire pressures, barely enoguh to keep TPMS from screaming to prevent horrible rollover, which still means my tires are over-pressure after 20 minutes.)
Alas, after two track days the tires were feeling old and hard rather than young and sticky. After three, they were worst, and cords were just starting to show on the inside of the right front tire. (The right front wheel is very slightly misaligned, an issue while I plan to have resolved during the winter maintenance season.)
With a need for another set of new tires, I opted for Bridgestone Potenza RE-71R tires, again in the fatter 235 width. Several friends have been happily running these tires and as they have been discontinued (Bridgestone will be replacing them with an upgraded version using a new compound) I was able to get a bargain set through Discount Tire Direct including heat cycling. The only problem was shipment via FedEx Ground, which was screwed up to the point of me cancelling the order only to be saved at the last moment when FedEx found the wayward shipment.
The new tires didn't have the glue-trap feel of the NT01s but felt capable and performed well on the track. Perhaps more importantly to me, they did not turn into ice skates when tire pressures skyrocketed. I ended up being so complacent as to not bother checking pressures after the last morning session. Here are the pressures I got around to recording:
Description Time Ambient LF RF RR LR Note before session 1 0737 69°F 36.5 37 36 37 31 31 31 31 reset after session 1 0823 80°F 36.5 37 35.5 35 after session 2 0924 82°F 38 37.5 36 36.5 after session 3 1026 86°F 39.5 38 36 36 lunch after session 5 1325 96°F 40.5 39.5 37 37 after session 6 1425 100°F 40.5 39.5 37.5 37 38 38 35 35 reset after session 7 1525 100°F 39 38 36 36 Chevron 1823 99°F 31 32 31 31 36 36 35 35 reset
This video (MPEG-4 version) features my best two laps of the day along with their prelude, from session 7:
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Copyright © 2021 Karl L. Swartz. All rights reserved. |
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