[VIDEO] Why Did I Crash - Episode 2
01-08-2019, 09:24 PM
#1
Track Rat
Thread Starter
[VIDEO] Why Did I Crash - Episode 2
I started this video series last week and just posted the latest episode to my channel. This is designed to help all of us learn from the mistakes of others at the track and since the two I've done so far were both C7 Z06s I thought I'd post this one here. Big thanks to the driver for being willing to share their data and making this possible.
In case you missed the first episode it's here:
In case you missed the first episode it's here:
The following 14 users liked this post by Poor-sha:
Carvin (01-09-2019),
dxbtune (01-24-2019),
fatsport (01-08-2019),
fpfaeth (01-09-2019),
FrankT1958 (01-12-2019),
and 9 others liked this post.
Popular Reply
01-11-2019, 01:06 AM
Tech Contributor
Member Since: Oct 1999
Location: Charlotte, NC (formerly Endicott, NY)
Posts: 40,089
Received 8,928 Likes
on
5,333 Posts
The car in the video is mine and I was driving. I had 305/660/18 front and 315/680/18 Pirelli Scrub Slicks. Cold Pressures were set at 26 psi and hot pressures after previous sessions were in the range of 32/33 psi across all 4 tires. The GM MR Calibration had been installed at the beginning of the year. The front alignment was set with -2.3 deg negative camber with +6.7 deg caster and about 1/32 of total toe in. Rear alignment was set at -1.7 deg camber with +0.7 deg of caster at each rear wheel with about 1/32 of total toe in and 0 deg thrust angle. The incident happened on the 10th lap after about 22 minutes of track time. My fastest lap was two laps before this where I turned a 2:07:90. The previous session I had turned a fastest lap of 2:06:90. I have turned laps as low as the high 2:03s over the last year.
Sean did the a great analysis and went into much more depth than he was able to when I first asked him to look at the data. he video shows I made a Rookie Mistake by applying too much throttle too soon. Whether or not I early apexed doesn't really matter as an experienced driver should be able to handle any corner entry since there are many things that can make them choose an off line entry. There are some things that a data recorder doesn't record. Tire Grip and Driver Focus are two of those things. T
From a Grip standpoint this event was the third event with these tires. They had 3 previous VIR track days and 2 Watkins Glen track days (or about 20 heat cycles) on them at the beginning of the day. I was at the end of my third 20+ minute session for the day when the incident happened. During the previous session I felt the rear tires starting to get greasy with the back end stepping out in several right hand turns.
From a Focus standpoint I was thinking about the run I wanted to make down the hill toward the Oak Tree corner (2 turns further).
That Focus led me to go full throttle too soon in the turn in an attempt to get that run down the hill and I didn't have the grip in the tires to do what I was trying to do.
All that defines a Rookie Mistake and that is what I told the Chief Instructor when he was filling out the insurance forms while I was being checked out in Medical. It turns out the mistake was a $7K lesson for me and hopefully others can learn from my error without spending that much money.
Bill
Sean did the a great analysis and went into much more depth than he was able to when I first asked him to look at the data. he video shows I made a Rookie Mistake by applying too much throttle too soon. Whether or not I early apexed doesn't really matter as an experienced driver should be able to handle any corner entry since there are many things that can make them choose an off line entry. There are some things that a data recorder doesn't record. Tire Grip and Driver Focus are two of those things. T
From a Grip standpoint this event was the third event with these tires. They had 3 previous VIR track days and 2 Watkins Glen track days (or about 20 heat cycles) on them at the beginning of the day. I was at the end of my third 20+ minute session for the day when the incident happened. During the previous session I felt the rear tires starting to get greasy with the back end stepping out in several right hand turns.
From a Focus standpoint I was thinking about the run I wanted to make down the hill toward the Oak Tree corner (2 turns further).
That Focus led me to go full throttle too soon in the turn in an attempt to get that run down the hill and I didn't have the grip in the tires to do what I was trying to do.
All that defines a Rookie Mistake and that is what I told the Chief Instructor when he was filling out the insurance forms while I was being checked out in Medical. It turns out the mistake was a $7K lesson for me and hopefully others can learn from my error without spending that much money.
Bill
01-08-2019, 10:44 PM
#3
Melting Slicks
Great analysis. Lots to learn for a beginner like me, and this is very informative. Thanks to the guys who submitted your PDRs, so others could benefit. 
01-08-2019, 11:24 PM
#5
Instructor
Great information. A easy way to break down the problem is using the percentages for the accelerator, brake, and steering angle. All 3 of those added together should add up to roughly 100%. Accelerator at 80%. Steering angle should be 20% or less with 0% brake. As its clearly outlined by the red, blue, and green laps. On the red lap accelerator was over 90% with 30% steering input. Over 120% and it got loose.
Look at it as if you have $1.00 to spend between steering, braking and accel on the track and the roadway. Spend $0.90 on accel, you have only $0.10 on steering. $0.50 on the brakes, $0.50 on steering. Anything over 1.00 and you're overdrawn.
Great thread, thanks for sharing the info and taking the time to help others.
Look at it as if you have $1.00 to spend between steering, braking and accel on the track and the roadway. Spend $0.90 on accel, you have only $0.10 on steering. $0.50 on the brakes, $0.50 on steering. Anything over 1.00 and you're overdrawn.
Great thread, thanks for sharing the info and taking the time to help others.
The following users liked this post:
Carvin (01-09-2019)
01-08-2019, 11:44 PM
#6
I started this video series last week and just posted the latest episode to my channel. This is designed to help all of us learn from the mistakes of others at the track and since the two I've done so far were both C7 Z06s I thought I'd post this one here. Big thanks to the driver for being willing to share their data and making this possible.
https://youtu.be/vCbmPL9PLps
In case you missed the first episode it's here:
https://www.youtube.com/watch?v=F32E7QCijJU
https://youtu.be/vCbmPL9PLps
In case you missed the first episode it's here:
https://www.youtube.com/watch?v=F32E7QCijJU
01-09-2019, 06:40 AM
#8
Le Mans Master
Member Since: Oct 2005
Location: Metro Detroit Michigan
Posts: 7,076
Received 1,817 Likes
on
1,085 Posts
Very nicely done, Poor-sha!
01-09-2019, 09:51 AM
#10
Melting Slicks
Great information. A easy way to break down the problem is using the percentages for the accelerator, brake, and steering angle. All 3 of those added together should add up to roughly 100%. Accelerator at 80%. Steering angle should be 20% or less with 0% brake. As its clearly outlined by the red, blue, and green laps. On the red lap accelerator was over 90% with 30% steering input. Over 120% and it got loose.
Look at it as if you have $1.00 to spend between steering, braking and accel on the track and the roadway. Spend $0.90 on accel, you have only $0.10 on steering. $0.50 on the brakes, $0.50 on steering. Anything over 1.00 and you're overdrawn.
Great thread, thanks for sharing the info and taking the time to help others.
Look at it as if you have $1.00 to spend between steering, braking and accel on the track and the roadway. Spend $0.90 on accel, you have only $0.10 on steering. $0.50 on the brakes, $0.50 on steering. Anything over 1.00 and you're overdrawn.
Great thread, thanks for sharing the info and taking the time to help others.
Last edited by fatsport; 01-09-2019 at 12:28 PM.
01-09-2019, 12:59 PM
#11
PTM Race setting is a force to be reckoned with! I barely even go into Sport 2. For me, Sport 1 is where all the fun is at.
01-09-2019, 06:47 PM
#13
Burning Brakes
Thanks for another interesting and detailed analysis.
I would love to see the entire lap leading up to the crash. The question that comes to my mind is why was the driver putting in so much steering angle while going aggressive with the throttle? I think the driver probably apexed too early all the up through the esses including turn 10. In the approach to 10 he is not using the whole track, he apexes 10 very early and is digging out with a lot of throttle. The early apex means he has to steer the car more to complete the turn and application of throttle yields a predictable outcome. The steering input is like braking only the front wheels while dialing up over 600 lb/ft of torque to the rear wheels. The data explains the how, but the video gives us the why.
I would love to see the entire lap leading up to the crash. The question that comes to my mind is why was the driver putting in so much steering angle while going aggressive with the throttle? I think the driver probably apexed too early all the up through the esses including turn 10. In the approach to 10 he is not using the whole track, he apexes 10 very early and is digging out with a lot of throttle. The early apex means he has to steer the car more to complete the turn and application of throttle yields a predictable outcome. The steering input is like braking only the front wheels while dialing up over 600 lb/ft of torque to the rear wheels. The data explains the how, but the video gives us the why.
Last edited by Bad_AX; 01-09-2019 at 06:47 PM.
01-10-2019, 01:15 AM
#15
Melting Slicks
Thanks for the videos. Really liked the data traces. I don’t push for early throttle at my HPDE and these crashes are a good reminder why I don’t. Not going to try and set lap time records in my weekend cruiser just dialing it back 25’ on braking or 10% throttle can make all the difference.
01-10-2019, 05:30 AM
#16
In the GM official video at VIR in a C7 Z06 with the magnetic ride calibration update, the driver almost loses it at the same spot, going over that crest, just past 1:03 into the video below. I'm also wondering just how unforgiving the Sport Cup 2's are (a case of "all or nothing grip"). I have the MPSS on my 2015 C7 Z06 3LZ M7, and noticed a big difference in acceleration when the tires are spinning and when the traction control kicks in, which is a straight line traction issue, and may not reflect the cornering characteristics of the tires.
01-10-2019, 08:14 AM
#17
Le Mans Master
Member Since: Oct 2005
Location: Metro Detroit Michigan
Posts: 7,076
Received 1,817 Likes
on
1,085 Posts
In the GM official video at VIR in a C7 Z06 with the magnetic ride calibration update, the driver almost loses it at the same spot, going over that crest, just past 1:03 into the video below. I'm also wondering just how unforgiving the Sport Cup 2's are (a case of "all or nothing grip"). I have the MPSS on my 2015 C7 Z06 3LZ M7, and noticed a big difference in acceleration when the tires are spinning and when the traction control kicks in, which is a straight line traction issue, and may not reflect the cornering characteristics of the tires.
https://www.youtube.com/watch?v=Hq0cvWZkv5I
https://www.youtube.com/watch?v=Hq0cvWZkv5I
Also sounds like he is using the sound of the rev limiter to tell him when to upshift.
01-10-2019, 09:02 AM
#18
Drifting
Hey I know that Z06, the driver, and have had intimate encounters with the T10 tirewall as well.
Thanks for taking the time to do this Sean!
Any update re your ZR1?
Thanks for taking the time to do this Sean!
Any update re your ZR1?
01-10-2019, 09:25 AM
#19
Drifting
Thanks for another interesting and detailed analysis.
I would love to see the entire lap leading up to the crash. The question that comes to my mind is why was the driver putting in so much steering angle while going aggressive with the throttle? I think the driver probably apexed too early all the up through the esses including turn 10. In the approach to 10 he is not using the whole track, he apexes 10 very early and is digging out with a lot of throttle. The early apex means he has to steer the car more to complete the turn and application of throttle yields a predictable outcome. The steering input is like braking only the front wheels while dialing up over 600 lb/ft of torque to the rear wheels. The data explains the how, but the video gives us the why.
I would love to see the entire lap leading up to the crash. The question that comes to my mind is why was the driver putting in so much steering angle while going aggressive with the throttle? I think the driver probably apexed too early all the up through the esses including turn 10. In the approach to 10 he is not using the whole track, he apexes 10 very early and is digging out with a lot of throttle. The early apex means he has to steer the car more to complete the turn and application of throttle yields a predictable outcome. The steering input is like braking only the front wheels while dialing up over 600 lb/ft of torque to the rear wheels. The data explains the how, but the video gives us the why.
He pinched the turn & didn't unwind the wheel to track out. Everything was solid until after the apex.
T10 falls off camber so if the car isn't positioned correctly and you are heavy in the throttle, the rear will come around, even on Pirelli scrubs which he was running...
01-10-2019, 10:15 PM
#20
Other than tires (crash with Pirelli scrubs versus GM official run with Sport Cup 2's), were there any other differences, such as the magnetic ride calibration update? In the crash video, the Z06 is going about 90 mph, while in the GM video, the Z06 is going 100 mph and at full throttle by that point. What you can't see in the GM video is how quickly or by how much the driver (Jim Mero?) corrected to recover from the rear end stepping out a bit.
There is also a video of Randy Pobst at Laguna Seca with the 2015 Z06 before the calibration update, and he's having to make quick corrective actions to recover from the oversteer in a few of the turns. Randy comments on the entry oversteer a bit after 6:00 into the video below, and it can be seen and commented on from 6:00 to 7:20 or so into the video.
There is also a video of Randy Pobst at Laguna Seca with the 2015 Z06 before the calibration update, and he's having to make quick corrective actions to recover from the oversteer in a few of the turns. Randy comments on the entry oversteer a bit after 6:00 into the video below, and it can be seen and commented on from 6:00 to 7:20 or so into the video.
Last edited by rcgldr; 01-10-2019 at 10:17 PM.