I hear this term thrown around a lot, but I don't have a clear understanding of what it means...

To me it always meant that I could steer left for turn in and hold a steering setting while off the throttle and on the brake. At that point as I started to ease out of the brake and back on the throttle the car would take a set and further steering inputs were not required. As I completely released the brake and pushed the gas to the floor the car would mostly straighten out by me just easing pressure on the wheel. In other words, the turn in and off are one long smooth operation without having any push or loose condition in the car. The car just "Rotates through the corner".

Bill

hobbymanbill - 02 April 2008 11:04 AM

To me it always meant that I could steer left for turn in and hold a steering setting while off the throttle and on the brake. At that point as I started to ease out of the brake and back on the throttle the car would take a set and further steering inputs were not required. As I completely released the brake and pushed the gas to the floor the car would mostly straighten out by me just easing pressure on the wheel. In other words, the turn in and off are one long smooth operation without having any push or loose condition in the car. The car just "Rotates through the corner".

Bill

Relates mostly to driving on pavement.
Imagine that the tires are rubber bands able to flex and move around the rim. In technical terms could be classified as slip angle.
Under braking and turning on entry, the majority of weight is on the front tires, when the car reaches the center of the corner usually there's no more braking and the car's balance and weight is just about equal on both right tires. A slight movement of the steering wheel to point the nose of the car to the inside of the corner WITHOUT sliding the car and just enough to "FLEX" the rubber bands (tires) so that pointing the car's nose further inside the corner is possible ALLOWS the throttle to be applied sooner and more aggressively because the car is now pointed a little straighter for the exit and allows more throttle and higher speed to be used.....
If all this happens without sliding the car then it will be quicker, sliding the car will slow you down below smoothly exiting. Car rotation can also be used to help drive around a pushing car.

hobbymanbill - 02 April 2008 11:04 AM

To me it always meant that I could steer left for turn in and hold a steering setting while off the throttle and on the brake. At that point as I started to ease out of the brake and back on the throttle the car would take a set and further steering inputs were not required. As I completely released the brake and pushed the gas to the floor the car would mostly straighten out by me just easing pressure on the wheel. In other words, the turn in and off are one long smooth operation without having any push or loose condition in the car. The car just "Rotates through the corner".

Bill

That's what it means to me as well in my past experience, nice explanation.

To me, "rotate through the corner" refers to the fact that the car (hopefully) turns on its yaw axis as it transitions from coner entry, to maintenance throttle, to corner exit. On corner entry the car is decelerating and will tend to understeer. As the car proceeds through the corner the weight will shift back and the car will slowly rotate on its yaw axis in a slight oversteer condition (driver preference is important here) so that the tail is correctly aligned on corner exit to acheive the maximum time possible for going down the straight at full throttle. If the car will NOT rotate in this fashion, and remains in an understeer or neutral condition through the corner, maximum exit speed will not be acheived.

It seems to me that Hobbymanbill's original explaination is saying the same thing, but from a pure drivers perspective, while other explainations, including mine, are more of an engineering description.

TopKart - 02 April 2008 11:54 AM

To me, "rotate through the corner" refers to the fact that the car (hopefully) turns on its yaw axis as it transitions from coner entry, to maintenance throttle, to corner exit. On corner entry the car is decelerating and will tend to understeer. As the car proceeds through the corner the weight will shift back and the car will slowly rotate on its yaw axis in a slight oversteer condition (driver preference is important here) so that the tail is correctly aligned on corner exit to acheive the maximum time possible for going down the straight at full throttle. If the car will NOT rotate in this fashion, and remains in an understeer or neutral condition through the corner, maximum exit speed will not be acheived.

It seems to me that Hobbymanbill's original explaination is saying the same thing, but from a pure drivers perspective, while other explainations, including mine, are more of an engineering description.

I guess the difference would be whether the car rotates for you or you have to induce the rotation.
Inducing a rotation without sliding the car is the mark of a great driver vs. a good driver..... Many drivers set their car up loose because they lack the ability to rotate a car without sliding it, so they let the car rotate for them. Hence the comment "Loose is fast".
When in fact a loose car is not going to be driven any faster through that corner (you would crash) but a driver with "good" car rotation skills would push a slightly pushing car beyond the speed of a loose car, because of the reason he can rotate around the push condition, making the car neutral in handling, and do so with confidence.
This is the difference between car rotation and driver induced car rotation. There is a difference between the two, both engineering wise and driving wise.....

Thanks for the great explanations everyone... I have noticed that during turns that cars close to the inside line have the front left tire a couple inches closer to the line than the back left tire. Is this considered part of car rotation?

RobsanX - 02 April 2008 12:53 PM

Thanks for the great explanations everyone... I have noticed that during turns that cars close to the inside line have the front left tire a couple inches closer to the line than the back left tire. Is this considered part of car rotation?

It could be. I can only describe what I felt, and since I was IN the car I couldn't always SEE exactly where the wheels and tires were in relation to the apex of the corner. It sounds right though. I can watch a driver through the windshield and tell you whether he is loose or tight or is "Rotating through Nicely". Generally if a drivers hands are Quiet or "steady" on the wheel from getting in to coming off, the car is handling to his liking. That is not always the case however, some actually "LIKE" a somewhat loose car since it allows to steer somewhat with the throttle. Loose is generally FAST. If that's the case you will see the driver putting small RIGHT inputs while coming off under acceleration. Tight is generally the opposite. Not being able to hold the car "DOWN" at the apex, and continual "LEFT" inputs while trying to get back to the throttle on exit. Tight gets you "in fast", loose gets you "off fast" the guy that gets on the throttle FIRST coming off, almost ALWAYS WINS. Hope that helps.

Bill

Mid-turn is where the real balance of the car shows itself. Understeer or oversteer on corner entry and/or exit is often driver-induced. In slow and out hard works everywhere but is difficult for many drivers ... road racers often seem better able to stick to the discipline. In mid-turn, the car can be said to be in a steady cornering state. Steady state cornering is the basis for skid pad testing, where a racecar transits a large diameter, continuous circle of asphalt at a steady rpm setting. The revs are gradually increased after a predetermined number of laps are run at the previous tach reading until the car either understeers or oversteers. It's a good real world test of chassis balance if you want to validate engineering data gleaned from various sources and applied to setup and you don't have to travel to a track to do it. Penske and others have on-site skid pads.

The mid-turn, steady state portion of a corner isn't very long relative to the total length of corners at any track, and is characterized by the left foot (if you drive properly) resting on a dead pedal (not the brake pedal) and the throttle held in whatever position it was in at the start of the mid-turn point. Neutral balance in this condition is critical to performance. Chad Knaus and the best of the rest know how to find it ... most of the time.

I'll leave all the technical nuances I can think of out of my post ... here's a good read:

http://books.google.ca/books?id=kyCWHRmf3OQC&pg=PA175&lpg=PA175&dq=steady+state+cornering&source=web&ots=blrGFyOsc5&sig=L7NTMYyq2J-kso_v7Em-s2BMl6E&hl=en#PPP1,M1

...

RobsanX - 02 April 2008 12:53 PM

Thanks for the great explanations everyone... I have noticed that during turns that cars close to the inside line have the front left tire a couple inches closer to the line than the back left tire. Is this considered part of car rotation?

You are describing a car that (probably) is oversteering because it is being forced around a corner of smaller radius than cars taking a wider line through the turn. Since the car is set up "loose," the tail will hang out a bit. Since the car now is moving about its yaw axis (the yaw axis is the geometric center of rotation in the horizontal plain--think of a record or cd on a spindle) it is "rotating" in a broad sense. Your question, however, is incomplete because we don't know what the attitude of the car was on corner entry or on exit. Therefore, we can't say for sure whether the car is "rotating through the turn." The best answer is "if it is being driven right and is set up right, then 'yes'".