ProCoach

Yes, in examining the braking (deceleration in longitudinal g's) execution of professional drivers in a longer (more than 100 ft or five car lengths) braking zones, the deceleration "attack" (or beginning of a braking zone) is sudden and substantial. The longer the zone, the longer that initial, high deceleration rate is held constant. There are small variations due to the fact that if the car has significant aero and the entry speed is high enough, the decel rate can be higher with the d/f and trails off SLIGHTLY as speeds go below 80-85 mph and the d/f goes away.

In nearly all cases, the deceleration rate (and you can infer by this the pedal pressure) goes down AT the point (or past the point, in slower corners) where lateral g's substantially build. But to repeat, there is that momentary zone where decel (the practical result of brake pressure) is constant and often extends RIGHT UP TO (and sometimes past, in slower corners) the turn-in point.

The greatest fault revealed in examining braking data is erratic deceleration rates (often due to momentary brake pressure release inadvertently when heel and toeing, which is what I saw in the trace teamking put up as his example) and/or significantly rising (panic) or falling (braked too soon) decel rates/distance before there is significant lateral acceleration recorded.

paver

Lolaman, what's d/f?
Thanks

FFaust

Down force.

mglobe

Nicely written Dave.

Veloce Raptor

Many thanks, Mike!

KaiB

Yew two are cute together!

Nice article also...

Dave 86 930 Fl

It's not so bad. I used to go through an entire box of diapers a day, now I get 2-3 sessions before i need to change them. Just one more consumable to add to the list.

Veloce Raptor

thanks

pontifex4

Alright, I'll live with it, and see if I can tune some of the shock out of the acceleration eventually. I'm really looking forward to driving an NA miata soon, actually: the turbo is fun, but being such a sissy about it isn't!

BBMGT3

Hello coaches!

I can't believe I visit Rennlist almost every day and have missed this thread. Awesome stuff.

Am a rookie racer and an experienced DE driver. I learnt most of what I know from spending about 200 hours in a CR125 shifter kart and having every "off" known to man when I first was learning to drive it. But I've found that the way it develops your steering ability is unbelievable, to the point that I am having a great deal of difficulty putting any car into a spin anymore (always seem to correct without noticing)

Am racing Touring cars and will try to move up to GTx when time and money permit. I DE a gen 1 997gt3. Questions below are related to the porsche - driven mostly stock on MPSC.

I have data acquisition but no video. A few questions:

- Is it normal to achieve higher lateral G's sometimes than long G's (cornering force is higher than braking force)
- as you approach the limit, is it normal to feel the car "float", especially at apex, and feel like any sudden input (including throttle) will result in oversteer/spin?
- How to develop the trust in the car, that at WOT on corner exit, it won't suddenly snap-spin on you? I just can't seem to get on the throttle quickly enough, always feels like there is a tiny bit more but that it will have dire consequences if I go for it, and will opt to have throttle chasing the steering (unwinding) How to get over that?
- Double Apex Fast corners & trailing throttle. Car feels like the rear wants to step out. Sometimes rear does step out, and at 90mph+ its not pleasant because I'm not too keen on wrecking my car (wrecking a race car is a surprisingly less troubling proposition...). Yet I feel like I am not getting enough out of the car.

Driving consistency is OK, usually in a 15 lap session I will have a half dozen traffic-free quick laps during which I will set times within 1s of my best. Sometimes will set best times in seperate sessions that are within 0.1s of eachother. That just tells me that I've hit some sort of plateau and I am very consistent at not going quick enough lol

Appreciate any tips!

Veloce Raptor

Welcome!

I will give my obsrevations, others should also.

1) Yes.

2) Yes, in many cases. This is how you know you have carried enough entry speed

3) Learn to roll on the throttle smoothly, starting early. In other words, get to throttle early, but maybe only 20%, then smoothly roll all the way to 100%. This loads the rear suspension & unloads the front suspension much more gradually, and gives you a much more stable car in which you have confidence the rear will stick. As opposed to just going WOT. This process doesn't take a long time--merely fractions of a seccond--but the lack of suddenness in it works wonders!

4) Seems to me either an alignment issue (rear toe?) or you are very tentative on the throttle there, which unweights the rear, which creates the tendency to oversteer. In other words, your fear of oversteer may in fact be creating it.

BBMGT3

Am pretty sure its not the rear toe, because I always get the car looked at before. I want to add steering lock, but am in a situation where the car is also slowing down. Since its a double apex,and the second apex is tighter than the first (you actually kinda miss the first apex), oh and there is a hard braking point right after.

Here is an example of the corner.
You can see it @ 40s in, and then again at speed @ 4:10, and then every couple of minutes after Driver is struggling with the car so maybe its not a good sample.

Then the other corner, clip from the 2010 24 hr race.

Again, don't mind the driver, he seems to be struggling a bit too, from 3:30 - 4:08, and again 5:45-

Veloce Raptor

LOL obviously different tracks. I have driven the Autodrome track, but not the Yas Marina one.

In the first one, it seems to me that the driver really needed to displace the first apex a lot, in order to get the car straighter & less bound up through the second one. It seems as if he was more driving them as 2 corners, point to point (curb to curb) rather than as one graceful arc leading to a short brake zone. So perhaps thinking backwards, which is something I always coach in complex corners like this one, would allow a better set up and entry, leading to a better, faster, more stable outcome?

BBMGT3

ok, makes sense. Since that "arc" has a decreasing speed, and you are invariably tugging at the rear as you turn in and then, brake hard (very easy to snap the rear out). I've fallen into the habit of starting my "arc" at one speed and then maintaining it throughout the double corner.

Good to hear you've driven the autodrome! Turns 1-5 are where the headache is. If I get T1 "quick", I bounce off the T2 kerb and am all out of shape for T3. Go too quick into T3 and you will miss T4, and then the two island kerbs are wishful thinking. If you manage to thread the needle, the car is really moving, and you just need to make it to T5 and then you've survived the first sector.

Would I be right in assuming that the "quickest" way through there is a path that feels like you are leaving a bit of time on the table in each individual corner?

Veloce Raptor

Yes, if you can "open up" the arc of the entry into the first apex, it makes the back end of the car much more stable, and unbinds the front end, so you don't give up too much into the second apex.

Regarding the Autodrome, are you using left foot braking anywhere in there to help gently rotate the car and settle the nose?