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Thank you for your experience. Racer360 review of my video indicated I was too far left at entry to carousel and should be where your car is, 1/4 to the left.
I use 4th gear. I breathed the throttle, but have not previously gradually increased throttle so at the apex I am at full throttle, just maintain a constant throttle to the apex and then when to full throttle.
Also I was not using all if the track at corner exit which indicates I could carry more speed in the 🎠
I disagree with the entry line placement being the reason why you're under the limit. That's too simplistic an answer. On the exit, I agree...
Extended periods of constant throttle means extended periods of "just under the limit," at least at the Outer Loop.
your fourth gear is a good idea. Your progressive throttle is a good idea. If you can be constant, then go immediately to 100% WOT, then there is a period that you are well under the limit.
You should ALWAYS have a "reaction" from the car if the control input changes are at the SMALLEST level difference.
If you're walking the tightrope of grip, a change in throttle the thickness of a credit card should MAKE A DIFFERENCE, IF you're AT the limit.
THIS is how the best drivers alter the trajectory of the car. It's ALSO why the "line" is determined FOR you, rather than a path you CHOOSE.
I understand that this is beyond a majority of driver's comfort level, but this IS how the fastest people drive.
Beyond a point, the line is determined by the conversation you're having with the car. And if the car is doing most everything you're asking it to do (i.e. change the line from left of center entry to 1/4 of the width out from the inside curb), then you are UNDER the limit.
Big time...
__________________ -Peter Krause www.peterkrause.net www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
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Been a while since I posted in this channel, been secretly reading in the back ground. two events ago my tired Traqmate finally died. While I was on the hunt for a newer data logger a friend lent me a Aim Solo DL2 so that I at least had something for the last race weekend of the year this past weekend at Sonoma Raceway. Even though it does not have the throttle, brake and rpm I had in the TM I am excited that I can finally use @ProCoach famous GSUM channel. In doing so I set a new PCA Spec Boxster Track Record by .6 faster and as always there is room for improvement. only two spots that the GSUM dips almost to zero. Former record was a 1:52.2 new record is 1:51.6 here is the data of the 51.6 and a link to the two back to back laps a botched shift on the second flyer cost me coming out of turn 11 or they would have been almost identical or a tad bit quicker. remember this is in a boxster so the speeds are slow lol.
So looking at how jagged the Gsum graph is I can see room for being smoother in places but how far from a "good representation" of GSUM is this? most of the dips in G are tied to stepping beyond the available grip and having to catch the car let alone Sonoma has so much elevation change and bumps?
I do need to give an extra shout out to Peter and Ross for their track walk of this track every bit of knowledge all adds up to "putting it" down when the track is good.
I just discovered this thread and spent several days reading through it. Fascinating - thanks so much to the coaches! I’m not sure if the thread is still alive, but I’ll try a question. This is about the VR response #3124 below. (BTW – VR opened my eyes to trailbraking at WGI several years ago, which was my breakthrough from a rote drive-by-number approach.) Here is VR’s response that has me a little confused.
Originally Posted by Veloce Raptor
Great question! Sorry for any confusion.
My point was that as you turn in (let's say to the left), most of the mass of the car is on the right front tire...more so if you're trail braking. If you're carrying good entry speed, that tire will at some point run out of available grip and understeer will ensue. Doing nothing at this point pretty much assures your trajectory will freeze where it is, until tire scrub slows the car enough for right front grip to return. When it does, suddenly, oversteer car occur.
The other approach, which I was advocating, would be to got to let's say 20% throttle. This moves a bit of weight off the RF tire and onto both rear tires. Doing this stops the RF from being overwhelmed. When this happens, grip returns, and the car can continue rotating into the apex...which then leads to starting to unwind the wheel and exit with more velocity as you roll on power. Going to 100% immediately would cause the understeer you mention. But just a little bit of throttle doesn't. It's you manipulating weight transfer in order to optimize tire grip
Does this make better sense?
I don’t quite get it, so maybe VR (or someone) can help me with how I’m looking at this wrong. My understanding is that turning depends on the front wheel angle and the slip angles at front and rear. In the case described, the front wheels are turned but overloaded, the slip angle is huge and nothing happens (understeer). If you go to 20% throttle, two things happen. 1) weight (and grip) transfers from front to rear and 2) you add to the “ask” of the rears by adding acceleration and maybe reduce the “ask” of the fronts (if you were trail braking) by removing the braking. In the front, if the reduction in braking is greater than the reduction in weight (grip), then I can see that the RF is less overwhelmed. But, if you weren’t trail braking, then you have only reduced the grip but not the “ask” so the tire should be even more overwhelmed. In the rear, if the addition to the “ask” from acceleration is greater than the weight (grip) increase, the slip angle will increase. Otherwise, it will decrease. It seems to me that you only help the understeer problem if you increase the rear slip angle (acceleration “ask” is greater than grip increase) and reduce the front slip angle (only in the case where you were trail braking and the reduction in front “ask” is greater than the reduction in grip). If you weren’t trail braking, then in the front you are only losing grip and the only way things improve is if the addition of acceleration “ask” in the rear increases the rear slip angle more.
So, it seems more likely to me that going to 20% throttle helps more through potential increase in rear slip angle than reduction in overload of the front (unless you were trail braking). Thanks for any insight.
Doug
I am glad you are finding value in this thread! I think that, which ever way it is explained or which ever theory you believe, the end result is the same. Namely giving the car what it needs to rotate better in a situation where it would normally understeer pretty badly
I don’t quite get it, so maybe VR (or someone) can help me with how I’m looking at this wrong. My understanding is that turning depends on the front wheel angle and the slip angles at front and rear. In the case described, the front wheels are turned but overloaded, the slip angle is huge and nothing happens (understeer). If you go to 20% throttle, two things happen. 1) weight (and grip) transfers from front to rear and 2) you add to the “ask” of the rears by adding acceleration and maybe reduce the “ask” of the fronts (if you were trail braking) by removing the braking. In the front, if the reduction in braking is greater than the reduction in weight (grip), then I can see that the RF is less overwhelmed. But, if you weren’t trail braking, then you have only reduced the grip but not the “ask” so the tire should be even more overwhelmed. In the rear, if the addition to the “ask” from acceleration is greater than the weight (grip) increase, the slip angle will increase. Otherwise, it will decrease. It seems to me that you only help the understeer problem if you increase the rear slip angle (acceleration “ask” is greater than grip increase) and reduce the front slip angle (only in the case where you were trail braking and the reduction in front “ask” is greater than the reduction in grip). If you weren’t trail braking, then in the front you are only losing grip and the only way things improve is if the addition of acceleration “ask” in the rear increases the rear slip angle more.
So, it seems more likely to me that going to 20% throttle helps more through potential increase in rear slip angle than reduction in overload of the front (unless you were trail braking). Thanks for any insight.
Doug
Manipulation of weight transfer is such a critical aspect and at the core of virtually every technique and piece of conventional wisdom.
I don't agree with getting on the throttle if you understeer while trail braking. You generally want less throttle (in a lift corner) or more brake (in a trail-braking corner). Less throttle (more lift) and more brake will transfer weight forward and temporarily increase front grip - trail braking 101! If the tire is spinning, easing a little more brake will transfer weight, temporarily increase the size of the friction circle, and help increase grip on that understeering front tire. But if that front tire is locked hard and sliding, more brake will just make it worse; the absolute first thing you need to do if you locked the brakes on corner entry is ease off the brakes to help get those tires spinning again. The loss of weight transfer means even more wheel unwinding. You're probably going to miss the apex if this happens, but if you came too hot into the corner or screwed up corner entry enough that you've locked your brakes, you're going to miss the apex, that's a foregone conclusion: stop worrying about driving to the apex, and work instead to stay on track, restore and maximize grip on your new line, and plan for your new corner exit point.
But the primary solution to corner-entry understeer is almost always just to fight instinct and unwind the wheel a little, which will help that overloaded front tire recover grip. You'll feel through the steering wheel as grip starts to return, and you'll feel it in your butt as your car yanks back into the turn.
Most novices respond to corner-entry understeer with more wheel and more brake, which just makes the problem worse. Takes a lot of practice to build the muscle memory necessary to unwind automatically without having to think about it.
Such a great description. You’ve just been given some of the best explanation of car dynamics ive ever heard. So difficult to express, so difficult to execute well. I’ll have to add that one other reason for understeer on entry is coming off brake too early and having absolutely now help with front grip when you need it the most-at the apex.
Manipulation of weight transfer is such a critical aspect and at the core of virtually every technique and piece of conventional wisdom.
Are you also a Skip Barber Instructor or School grad? This is the core principal of the SBRS curriculum foundation, dating back forty-five years.
Dion von Moltke, of Racers360, has very well articulated achieving not only the avoidance of corner entry and mid-corner understeer, but also the avoidance of "dead time," the distance covered where you're done braking but not yet pointed in the direction you want to go, when he talks about ending the braking at or around the apex area. This is a universal execution by top level pros, you can hear it by the engine note and where it is the lowest.
Great post, but I would also add that IF you have to react to understeer by opening the wheel, BEFORE you are on an exit trajectory or responding to throttle application balance change (a desirable one), then you need to FIX what caused the understeer to begin with.
Almost always the result of overdriving the entry of the corner, often the result of finishing braking too early.
Are you also a Skip Barber Instructor or School grad? This is the core principal of the SBRS curriculum foundation, dating back forty-five years.
Thanks! High praise coming from you. And no, I'm not a Skip instructor or grad, but I have read Skip's book. My biggest a-ha moment as a novice was seeing the coefficient of friction corves for tires, and the 2nd was understanding the physics of why slip angle exists and changes with contact patch shape; between those two it just explains so much of what we know anecdotally to be true, but few people understand WHY. Helps that I'm a PhD engineer! I'm actually primarily an autocrosser, but I've done more than a few track days, and have instructed a lot of novices; the skills and physics are pretty universal. Often tough to explain difficult concepts in ways people can understand, though. Even tougher still to actually put this into practice. Dion does an absolutely fantastic job of both explaining and driving, he's got a real gift. His trail-braking pressure graphs he seems to have to draw and repeat on every video he does are really helpful.
It annoys me that so many instructors teach students to get all braking done in a straight line prior to corner entry. Yeah, trail-braking is a more advanced technique and can be dangerous, but so can inducing understeer at corner entry by lifting off the brakes at turn-in, causing an abrupt rear weight transfer when the suspension rebounds. I've done course-walks with experienced drivers that had no idea trailbraking was a thing - none of their instructors had ever told them, and they clearly never picked it up solo.
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My favorite anecdote about eliminating dead-time is the Top Gear episode where Richard Hammond drives the Formula 1 car; it never ceases to amaze me how many students have seen this, and it's a pretty poignant scene! At one piont towards the end of the segment, he's going over telemetry data with the team engineer:
Engineer: There a big gap between when you're lifting off when when you're braking. You should be coming straight off the accelerator, and going straight on the brakes straight away, there's no need to have that big gap in there.
Hammond: Did you say a big gap? How big a gap is it?
Engineer: Half a second. Should be straight away!
Hammond: Massive, isn't it!
Would love some thoughts on my most recent fast lap on Summit Point Main. Personal best on this track of 1:27.87 in my base 981 cayman, and first time below mid 1:28’s. It would have been a bit faster but for traffic at the end.
Generally a very solid lap! Obviously, getting held up on the main straight killed your time. IMO that was the single largest time sink of this lap. Beyond that, there are several places where, on a straightaway, you are not on 100% throttle all the way to the next brake zone. Look how throttle dips slightly and then goes back to full (not coinciding with upshifts). One example is just before the bridge after 9, but there are other examples. In addition, there are some fast corners (such as 9 & 10) where you can roll to a bit more throttle position a bit sooner. A 1 mph gain in a couple of places like these can yield some real lap time advantages, due to the length of the full throttle zones that follow.
06-28-2020, 06:14 PM
And no, I'm not a Skip instructor or grad, but I have read Skip's book. My biggest a-ha moment as a novice was seeing the coefficient of friction corves for tires, and the 2nd was understanding the physics of why slip angle exists and changes with contact patch shape; between those two it just explains so much of what we know anecdotally to be true, but few people understand WHY. Helps that I'm a PhD engineer! 
I'm actually primarily an autocrosser, but I've done more than a few track days, and have instructed a lot of novices; the skills and physics are pretty universal. Often tough to explain difficult concepts in ways people can understand, though. Even tougher still to actually put this into practice. Dion does an absolutely fantastic job of both explaining and driving, he's got a real gift. His trail-braking pressure graphs he seems to have to draw and repeat on every video he does are really helpful.
