A Crash Course in Limit Handling

A certain video recently sparked a large discussion that made it clear a lot of people haven’t been given the best picture of how these machines we love behave at and beyond the limit

(Hint: it was this one
This Is What Happens When A Douchebag Tailgater Meets A Cretinous Brake Checker : https://www.carthrottle.com/post/this-is-what-happens-when-a-douchebag-tailgater-meets-a-cretinous-brake-checker/ )

Without dwelling too much on it or naming names, I want to give you guys a good idea of what, where, when, and why with this stuff, because it clearly isn’t always intuitive. I think focusing on the car might be a good place to start. We’ll start with exciting stuff, namely, how we accelerate, and look at each layout’s ugly (or not-so-ugly) habits

Front Wheel Drive

This is a good one. The layout the vast majority of us are familiar with. The front wheels pull you along, and steer the car. They’re quite busy, and when you try to ask too much of them, they get frustrated, and decide they’re not doing any of it. Tires squeal, and you’re no longer accelerating OR turning well at all. You turn the wheel more and more, but the front wheels just won’t turn the car like you’re asking them too. The car is understeering

Ok, so I buy a sweet rear drive machine and I'm done with understeer?

Front wheel drive isn’t the only thing at work here. Especially not when you’re running into understeer at lower speeds You need to take a closer look at the real boss here, the shot caller, the Don, the Commander-in-Chief

Tires

These are the big deal. The workhorses that brings us sub-2 second 0-60 times, the unsung heroes that manage 4-digit power figures, and speeds exceeding 260 miles per hour. With a warranty

These are going to steal the show for a minute, but I promise it’s worth it. Remember our issue with understeer? You try to accelerate in the corner and can’t turn? And then you hit the brakes and deal with the same thing? You can curse at the car, but really, you’re asking the Don, the Big Kahuna Burger, your tires, to do something they don’t want to do.

Tires do all those cool things I talked about and more, and do them phenomenally well. Frankly the physics and engineering at work are ingenious. But they fall short in one area, and its a very important one to understand: tires HATE multitasking. And hate is a strong word, but its more than appropriate. Tires can handle massive braking and accelerating loads without skipping a beat. They can handle very large lateral forces as well. But the moment you ask them to do both at once, it starts to fall apart. And thats a vital thing to understand on the track but more importantly on the road

"Brake in a straight line" ; "Don't use the throttle until you're ready to go flat out"

These are both sound advice from very fast drivers.

The first, is Ben Collins. The Stig

The second, Jackie Stewart

Both tame racing drivers are describing the same very important idea. If you can give your tires one job at a time, you will be faster. You’ll also be safer

Back to What We're Here For

I’ll try to do this without ruffling feathers, but sheer driving pleasure is my segway into the other main layout, rear wheel drive. Yes, there are very good front wheel drive driver’s cars. But I believe rear wheel drive is the top of the ladder, and its very hard to do better when looking for a connected, balanced, driving experience. Throw the books at me, but I’ll make my case simple, and move on

There is no front wheel drive 911

The simple reason being, there is much more control to be had from a rear wheel drive car. You can still run into understeer, just like before, but the rear wheel drive brings something new to the table. Being pushed forward instead of pulled along does something special

Oversteer

This time around, asking too much of the tires does something new. If I ask the tire to accelerate and turn the car, I can lose traction only in the rear. The rear swings towards the outside of the turn, pointing the car further towards the center of the turn. Oversteer. This doesn’t sound great, or fast, until you look at it as a tool. With small, controlled slip, you can now make mid corner adjustments and adjust the car’s path even with the front tires already pushed to the limit. When a driver talks about the car “rotating” through the corner, this is what they’re talking about.

If one of these sounds much easier to control, you’re right. Understeer is much easier to handle, because its somewhat one-dimensional. You’re going too fast to turn, you need to slow down.

Here’s where we get to the glaring hole in my explanation. Most factory cars are set up to do this, rear drive as well. Understeer happens under acceleration and braking, but oversteer only seems to happen with accelerating… why?

I said before that factory cars are set up to understeer most of the time. How?

You thought we were done, but alas, tires again. We went over the fact that tires don’t like multitasking, but didn’t go over the fact you have 4 of them, and they handle loads in the front, the back, the left, and the right. How those loads are distributed decides how the car behaves at the limit. Cars for the general public put the majority of the cornering loads on the front wheels, so the rears always maintain traction longer than the fronts do. The car isn’t exploiting all of it’s cornering potential, but the consumer is less likely to crash if they do attack a corner too fast, or brake and corner too hard

A race car’s cornering loads are very well balanced. It’s faster. each tire carries as much load as possible when the car is driven in anger. As a result, race cars will sometimes oversteer under braking and cornering, or even oversteer while steady speed cornering. An issue the general public isn’t all that prepared to deal with.

Oversteer is less favorable for manufacturers because its much more difficult for people to deal with. Oversteer takes finess, oversteer takes quick decision making, and there isn’t a generic fix to it like understeer. You have to steer into the slide, you have to be smooth, you can’t over correct, and you have to know what you’re doing. Oversteer has it’s own sport, but its not the easiest things to teach millions of drivers. So our cars get nerfed a little.

Hope you guys enjoyed the piece. And I hope it was informative. These are very long topics that people write books on, I tried to keep it somewhat short. I would love to focus on how to actually drive at the limit in another post if you guys are interested