Again, I feel forced to present the world famous...
Lessons on mid/late apex for beginners, by Ciro.
The line you adopt depends on several things. I quote myself.
NOTE: THERE ARE NO EARLY APEX CURVES UNLESS YOU WANT TO END LAST... or unless you want to read A LOT.
The mid/late apex depends on:
- the radius of the curve.
- the power of your car
- the grip of your car
- the distance between curves
- the sideslope and type of transition between curves
1. Radius
On a large radius curve you are fairly fast while taking the curve. Because you're fast at mid curve, there is no point in taking the late apex. So, mid apex it is.
On a small radius turn you gain little from mid corner speed. The time you spend around a tiny corner is small. It's small enough to make this an area you should despise when looking for shorter lap times.The faster you push the right pedal, the faster you'll get out of this area. You want exit speed and you want it now! Late apex, by all means.
2. The Power of your car
In command of a low powered car you want to point to a mid apex so you can carry all your meager speed through the curve, because the puny thingie engine you have in your back won't respond on exit.
On a high powered car you look for a late apex. So, you have a loooong exit ahead of you, while your glorious engine pushes you against the back of the car and gives you the fast exit you are looking for.
3. The grip of your car
A high grip car, with slicks the size of my posts is not the same as Green Powered Dude Reload electric car with bicycle tyres, sure. So, it will give you the ability to treat tight corners as if they were corners with larger radius. Conclusion: take the mid apex.
In a low grip car what's the use of trying to carry a high mid corner speed? You under steer as hell and end up without a racing line. You use raw power (hopefully) to "straighten" the car. Use a tight late apex corner. Yeah, I know this is confusing. You have to test that. Go.
4. The distance to the next corner
If there is 20 meters to the next corner, what do you gain from exit speed? Zilch. You take mid apex, get a fast midcorner and brake in time for the next one.
Now, if there is a long, long straight after the curve, by all means, take a late apex, get all the acceleration you can on exit and laugh happily. Believe me, there will be a HUGE difference when you can accelerate early between you and the mid apex guys at the next entrance.
5. Sideslope and transition.
Nobody understand when I explain this. Read about road design and we'll talk later.
I would be very grateful if any racer here can give me his opinions, these are mine. There might be other factors. Theoreticians, guys, please abstain. Those claiming that John Doe is a "natural late apexer", pleeeze... if that's the case, then John Doe is an ·/&=%$hole.
raymondu999 wrote:The purple line is a late apex line (Schumacher) and the dotted line is the geometric/racing line (Button)
Actually I believe that Schu tends to stick closer to the geometric line, but he then uses throttle to induce oversteer on apex so as to straight the car earlier and accelerate as if he was late apexing (his "power circle")
Caito wrote:What happens with JB in my personal opinion is the following:
Given a generic lateral force vs slip angle
There's a maximum. Let's say the maximum is at 100 grip units. That would be the ideally fastest lap. But there are two ways of getting 90 grip unis. One is below best slip angle and the other is above best slip angle. I believe Button manages to stay below the maximum.
At higher slip angles portions of the tire patch are sliding, and you get less increase in lateral force with an increase of slip angle. This is called the transition region. As the curve tops out, more of the contact patch is sliding and the tire produces less lateral force. After the peak of the curve, lateral force can fall off 30% within a few degrees of extra slip angle. At these high slip angles most of the contact patch is sliding, producing a lot of heat and wear.
Bye!
Where have you found "at higher slip angles portions of the tyre patch...,ect."?
You can read on most good books, such as Tune to win, Tires suspension and handling, etc.
There are in the last book models of a tire which help you understand the curve.
A really simple explanation would be that you can imagine the contact patch like being lots of spring sideways, pointing from left to right. Lot's of them top to bottom of the contact patch.
As you increase slip angle those springs start to extend, thus increasing side force.
As you increase slip angle, all springs stretch to a maximum, giving maximum cornering force from that slip angle onwards. A further evolution is that as you increase slip angle beyond the point that all springs are at their maximum you start to geerate heat, which ends up reducing the cornering force. So now the slip angle curve starts to fall once you reach a maximum.
As said before, if we made a bad assumption and say its quadratic, there are 2 points in which you can reach 90% maximum grip. Before and after maximum grip. Both would give the same lateral load, but over maximum grip would be generating more heat and wearing the tires faster.
raymondu999 wrote:while JB brakes earlier, then carries more speed through in a more conventional racing line.
I don't know much but I remember clearly in an issue of F1 racing magazine that this was exactly the same as Schumacher's style (and Mansell's). That a bucket of dripping paint on their cars would draw the shortest line around the circuit. Right on the friction oval of tire grip, smooth transition from braking (long. grip) to cornering (lat. grip), right at the limit of the tire model. That was Schumacher's style on entry AND exit.
How is it that, if that is also Button's style, they are so far apart in performance (or are they?) hmm. I don't actually know.
F1 car width now 2.0m (same as 1993-1997). Lets go crazy and bring the 2.2m cars back (<1992).
To be fair a "circular" line as well as late apex should theoretically separate lateral from longitudinal load; though the straight-ish exit of a late apex would still have a bit of lateral loading.
But I do get what you're saying. Brake in a straight line (100% long.), circle the corner at a constant velocity; at the edge of grip; (100 lat.); and finally when the car is straight again power out (100% long.)
It's been said that some tyres (including the Pirellis this year) get saturated easily if you load it with both longitudinal AND lateral loading requirements (i.e. it's good with longitudinal alone, it's good with lateral alone, but if you mix the two you won't get the optimum lap time).
Autosport a few months back also mentioned this; and said that it was one of the reasons that Vettel has been so good on the Pirellis; he has been able to isolate the lateral from the longitudinal the best; and so can access a lot more grip while keeping the tyres quite intact; which really was his strength starting from Turkey
raymondu999 wrote:while JB brakes earlier, then carries more speed through in a more conventional racing line.
I don't know much but I remember clearly in an issue of F1 racing magazine that this was exactly the same as Schumacher's style (and Mansell's). That a bucket of dripping paint on their cars would draw the shortest line around the circuit. Right on the friction oval of tire grip, smooth transition from braking (long. grip) to cornering (lat. grip), right at the limit of the tire model. That was Schumacher's style on entry AND exit.
How is it that, if that is also Button's style, they are so far apart in performance (or are they?) hmm. I don't actually know.
Please, can you tell me what number, month and year was that issue of F1 Racing, and how was the article called?
Thank you,
mariano
