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Sebring T17 dangerous tire walls

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Old 01-26-2015, 10:27 AM
  #31  
KaiB
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So, always look at what leads up to the desired input to see WHY you can do that so EASILY!

In virtually every case, in virtually every situation at almost all tracks, THIS rings so very true.

Thanks, well worth remembering.

(edit to add) I ask myself why I'm comfortable at certain points and try to figure out where I can push a bit from that question.
Old 01-26-2015, 02:42 PM
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mkd944
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Originally Posted by ProCoach
One of the more common errors IS for people to begin to open the wheel prematurely in a heavy (even modified) street GT car, because they feel ok, then they whack the throttle because they again, feel ok, then the car widens its arc prematurely and unexpectedly (aided by the bumps AFTER the bridge), then they have to get out of the throttle. BAD news! <grin>
Good luck!
Having just been at Sebring with Chin this past weekend, I can see how this could happen. On this line coming under the bridge, there was a particular bump that, when I hit it, made me aware that I needed to provide more right turn steering input as the tire wall loomed ahead. I was in DE mode and was leaving some margin for error but in competition, where drivers are using every inch of real estate, keeping the wheel and throttle open, I could see this happening.

BTW - In my previous post, I talked about the plastic/rubber sheeting in front of the tires before the bridge. That sheeting is also on the track out in T17 but it does not start until about 15 feet past where these accidents took place.
Old 01-27-2015, 07:34 PM
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Juan Lopez
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Originally Posted by ProCoach
JLS's and VR's posit that "you should be WOT before the bridge," and while that IS the first and a most laudable goal, it's NOT that simple...
Amen and a successful execution starts way before the bridge.

Looking at the SRF line, I think he was trying to reduce friction, sealed motor and all considered. Glad to hear he came out OK. Tire wall, oof
Old 01-27-2015, 08:01 PM
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The part I find scary is that someone can be doing it all the right way and yet become part of someone else's accident
Old 01-27-2015, 08:03 PM
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Originally Posted by gums
The part I find scary is that someone can be doing it all the right way and yet become part of someone else's accident
True anywhere, Frank, I'm afraid!
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Old 01-27-2015, 10:29 PM
  #36  
Veloce Raptor
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Peter, who is JLS?

I am not sure I have advocated this. Rather, I have advocated getting all the rotation done by the bridge (in other words, not adding any more steering input after the bridge) and spending as little real estate as possible at one's minimum velocity for that (or any) corner.

Originally Posted by ProCoach
My opinion is that the difference is due to the smaller, lighter, underpowered cars "driving" out to then edge of the track, fully utilizing the real estate to the track out point in the quest for "straight wheel soonest" eliminating steering thrust resistance and less inhibition of forward speed. All these cars (SRF's) have sealed motors, so the only way to get off the corner quicker than the next driver is to get the wheel straighter, sooner (assuming vMin occurs at the same point on track and the start and rate of throttle input is the same). That said, for the SRF's in the front, this is less so because they are going quick enough (and accelerating sooner and harder) so that the car is carrying" them out to the far left edge of the track, just as the pros do at the 12 Hours in both GT cars and prototypes. I used to believe, as Randy has pointed out, "he (or she) who is on WOT first wins," and also JLS's and VR's posit that "you should be WOT before the bridge," and while that IS the first and a most laudable goal, it's NOT that simple... After studying the VERY fastest drivers in their particular cars through and out of this corner, it has become apparent that they have shorter distances covered at vMin (by a good margin), are generating more constant slip angles (further towards the outside edge of the friction circle) and HAVE to "balance the car" (and the available tire grip, managing the exit radius) by a more progressive application of the throttle. Basically, operating closer to "the limit" for a longer period of time. In my analysis of even very good club level drivers, it's apparent that if you are overslowing approaching the addition of steering input to turn under the bridge, overslowing AT the addition of that steering input and AT ALL late on throttle rate of change UP and AFTER the steering input (hence immediately before and under the shadow of the bridge), you HAVE ALREADY overslowed and, OF COURSE, you can go to WOT sooner. So, always look at what leads up to the desired input to see WHY you can do that so EASILY! Hahahaha! A simple video review of throttle position and GSum can tell you all you need to know and most drivers are suffering from a lot more "hang time" than they remember doing in the car, at that point. The key is to balance the total grip of the car through that entire transition. KEEP THAT GSum HIGH! NO DIPS! But that does carry significant risk... Build up slowly. I ask people I work with all the time to track out fully, often maintaining a consistent steering angle input while balancing carefully the widening exit arc altered primarily by the ACCELERATOR, rather than opening the steering. One of the more common errors IS for people to begin to open the wheel prematurely in a heavy (even modified) street GT car, because they feel ok, then they whack the throttle because they again, feel ok, then the car widens its arc prematurely and unexpectedly (aided by the bumps AFTER the bridge), then they have to get out of the throttle. BAD news! <grin> The "Go/No-go" analysis is constant and ongoing. For every foot forward, you need to plot the angle and yaw of the car on exit so you can "see" where you're going to end up. Ideally, in a GT car with juice, you are constantly (and hopefully) steering a little MORE than the arc you are drawing with the car, offset and influenced almost totally by the position and rate of change of your right foot... Good luck!
Old 01-27-2015, 10:51 PM
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My friend Juan, VR. We're all saying the same thing. I'm just asking people not to fixate on that goal alone.

You know and I know (we ALL know), based on the incredible amount of data and discussion on this very corner, how tough it is!
Old 01-27-2015, 10:51 PM
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Originally Posted by Juan Lopez
Looking at the SRF line, I think he was trying to reduce friction, sealed motor and all considered. Glad to hear he came out OK. Tire wall, oof
Agree...
Old 01-27-2015, 11:20 PM
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I've never driven Sebring so I have never paid much attention to in car video. THIS is a fascinating discussion however because one watch of the crash video in the original post makes it glaringly obvious that this is a difficult corner that somehow confuses one's instincts. What bothered me watching it at first was that to my eyes the driver turned in WAY early and thus apexed early too. As only an HPDE driver with a bit of racing school experience I'm sure that my lines are conservative. Especially since I spent most of my track time in an Audi. Your discussion of apexing before the bridge looks wrong to my eyes. Testament that it is a difficult corner to wrap ones brain around. I've got to get down there soon. bucket list track. Hope you guys don't mind my posting occasionally. All I can give you is the 60 year old advanced student's perspective. BTW --- Thanks to all of you who instruct and make this stuff possible. I get a bit uneasy in the right seat.
Old 01-28-2015, 09:59 AM
  #40  
Veloce Raptor
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Ah now I understand you, Peter!
Old 01-28-2015, 10:19 AM
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Juan Lopez
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Originally Posted by Veloce Raptor
Peter, who is JLS?

I am not sure I have advocated this. Rather, I have advocated getting all the rotation done by the bridge (in other words, not adding any more steering input after the bridge) and spending as little real estate as possible at one's minimum velocity for that (or any) corner.
Me
Old 01-28-2015, 10:28 AM
  #42  
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Originally Posted by Veloce Raptor
Ah now I understand you, Peter!
I'm guilty of too many words sometimes, VR!
Old 01-28-2015, 11:36 AM
  #43  
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Originally Posted by Veloce Raptor
Ah now I understand you, Peter!
Dude!

Just get a bit more GRANULAR, it'll be alright then.
Old 01-28-2015, 11:55 AM
  #44  
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Originally Posted by KaiB
Dude!

Just get a bit more GRANULAR, it'll be alright then.
I'm NEVER going to live that down! Hahahaha!
Old 01-28-2015, 03:04 PM
  #45  
Veloce Raptor
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You guys are hilarious!


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