"Mr. Toad" at Buttonwillow (29 May 2021)"Mr. Toad" at Buttonwillow (29 May 2021)
 Hunting Bavarians |
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 Evening light |
 Friday sunset |
 Rolling in the dust (Leung Kwok photo) |
 Mr. Toad and me (Greg Epstein photo) |
 Photographers and their cars (Leung Kwok photo) |
 Hanging out with friends |
 (Greg Epstein photo) |
 Fuel stop (for the drivers) |
 Waiting ... |
 Ready to roll in the pits (Leung Kwok photo) |
 Finished (nearly) tire |
 Finish socks |
 Plenty of OPR (Other Peoples' Rubber) |
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 Post-track indulgence |
Buttonwillow has many different configurations; this day used the Race #13 configuration, clockwise (CW) in the morning then counter-clockwise (CCW) in the afternoon. The map is weird because for some reason Buttonwillow Raceway always draws their maps with north at the bottom. It's very disconcerting to see East Loop on what should be the west side of the map.
(Note: Hover over any turn name in the text to highlight it on the map.)
 Best lap of session 1 (2:13.873) |
 Best CW lap (2:13.698) |
Once again, the Big Brake Kit (BBK) enabled an enormous reduction in lap times. At The Streets of Willow Springs in February, when I was just learning to use the new brakes, I shaved 1.868 seconds off my previous best lap time. At Laguna Seca in March, on a very familiar track and now with more confidence in the new brakes, even the warmup session resulted in a nearly 2-second improvement, and my best lap was 4.445 seconds better than my previous best.
This time, the warmup session yielded a 6.820-second improvement, and by the end of the morning I had improved my lap time by 6.995 seconds relative to my first time at Buttonwillow.
In addition, the runs on either side of Phil Hill joined the 100-mph club. The lead-in hit 101.0 mph, up from 88.1 mph. The BBK undoubtedly helped but carrying more speed out of Riverside and maintaining full throttle through the left kink was also part of the improvement.
Relative to February, running in this direction was mostly about refinement.
Cotton Corners required constant self-reminder to go deep for a late apex at the first two turns, which led to a faster cresting right turn leading up to Grapevine.
Club Corner improved when I realized that the apex "turtle" is quite smooth and could be used to expand the radius of the turn, making it faster.
Bus Stop, or rather the kink at the end of it, continued to be a challenge but I made incremental improvements.
Sweeper and I made peace and I consistently nailed the sharp exit into the crucial start of the Esses.
The Esses are important because they lead into the fastest portion of the track. A good entry from Sweeper is critical but so is maintaining full throttle all the way through this sequence of chicanes. Early in the day, I backed off slightly for the last turn but worked up to staying at full throttle; combined with late braking this cemented 110-mph speeds before braking for Sunset.
Sunset
itself could probably be driven a little faster, something I'll focus on
next time. I don't remember noticing that in February but then I was more
concerned about braking.
 Best CCW lap (2:18.505) |
For the four afternoon sessions, we ran counter-clockwise, or anti-clockwise since Lotus is British. Similar to Thunderhill last September, running "backwards" felt weird at first, though doing so at Thunderhill and then at The Streets of Willow Springs in February helped guide my preparation for the afternoon sessions.
I expected this direction to be slower, in large part because the build up from the Esses into the fast straight before Sunset isn't an asset on the reversed course, but I ended up being less than five seconds slower than in the morning.
Fatigue was a factor by mid-afternoon. We had run four 20-minute sessions in the morning, then started the afteroon with a 25-minute session, so by the time I was getting used to the funny direction I had spent over two hours on the track. Temperatures in excess of 90°F (32 C) didn't help.
Sweeper is easier in this direction because there's no decreasing-radius exit. Instead, one can build up to full throttle for the run to Phil Hill.
Phil Hill is much like it is in the other direction: a blind kink at the top of a hill. Again, once one knows what to expect, it's pretty fast and once the car settles full throttle is again in order.
Riverside is farily fast but coming off a fast straight I was wary and braked a little at the start. I think I could have carried more speed and worked on that as the afternoon progressed, though fatigue held me back.
Truck Stop looks like a slight left kink, but the track is wide leading into it and I found it to be much faster than I had anticipated.
Bus Stop, or rather the kink leading to it, is my biggest challenge in the clockwise direction. I was surprised to find myself more comfortable with it running "backwards."
Grapevine was deceptive. On a map, it looks like a simple matter of braking after carrying a lot of speed from Club Corner, and I found that I needed to scrub off nearly 30 mph, but the surprise is that there's a slight crest right where you want to start braking. I ended up braking there and letting ABS help me out. I also found that I could carry more speed through the turn than I thought.
Cotton Corners, and the left turn leading into it, was an exercise in reminding myself that the most important turns are those that lead onto a straight. Working back from that, sacrificing some speed in these turns and a late apex at each set me up for a faster run on I-5.
Off Ramp worried me as it's a sharp turn and, in this direction, it's a decreasing-radius turn, a dangerous sort of beast for the unwary. This was similar to Turn 8 (Bowl) backwards at The Streets of Willow Springs in February and I followed a similar plan, slowing in the broad part of the turn followed by hard braking and a downshift before a tight turn and then accelerating through the apex. It worked well.
Sunrise required some experimentation since I wasn't sure where to shift back to 4th gear after Off Ramp. Although the stretch between the two turns is pretty fast I found it best to stay in 3rd gear and aim for a slightly late apex, using the lower-gear power to launch onto the front straight before shifting up at the exit from Sunrise.
Sunset
and the straight between it and the
Esses
is the fastest part of the track when running clockwise. Reversed, what was
a build-up to speed works, er, in reverse and I wrestled with where to brake for
Sunset
and how much speed I could carry into the start of the
Esses.
I braked lightly before the last of the
Esses
in order to get a good start to
Sweeper.
I've finally gotten a good handle on tire pressures, helped somewhat by the Nitto NT01 tires which seem to handle modest overpressure without turning into ice skates.
Description Time Ambient LF RF RR LR Note before session 1 0805 69°F 38.5 39 38 38 31 31 31 31 reset after session 1 0842 75°F 37.5 38 34 35 after session 2 0943 79°F 39.5 39.5 35 36 36 36 - - reset after session 3 1045 82°F 39 38 36 36 after session 4 1143 85°F 38 38 36 36.6 before session 5 1256 85°F 32 33 33 33 after session 5 1339 90°F 36 38 36.5 36 after session 6 1444 91°F 39 38.5 37 37.5 after session 7 1542 92°F 38 38.5 36.5 37 after session 8 1644 93°F 37 38 36.5 36.5 Gilroy 2200 59°F 30.5 30.5 31.5 32 36 36 35 35 reset
In addition to tire pressures, I used a pyrometer (thanks to Howard Wise) to measure the temperature of the brake rotors after some sessions. These measurements were after both some cool-down driving in the paddock and then measuring tire pressures so they are significantly cooler than the peak on track. I measured at the top of the rotor surface, through the wheel. The highest temperatures were at the end of session 3, which included my best lap time of the day:
Wheel °F C LF 340 171 RF 380 193 RR 180 82 LR 181 83
Brake-pad temperatures right off the track would be more interesting, though more than data I need cooling ducts so I can (hopefully) stop worrying about fried brakes.
To combat the GPS errors
encountered at Laguna Seca in March I bought a
Dual XGPS160 GPS receiver.
Alas, although it connected with my iPhone and TrackAddict recognized it,
TrackAddict never got beyond "GPS acquiring" and I was left with little
choice but to use Apple's GPS, which again exhibited data drops.
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Copyright © 2021 Karl L. Swartz. All rights reserved. |
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