In this video I discuss the common definition of understeer and why it’s incomplete. In addition, I show you the full blown technical definition of understeer.

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Video Transcript

Hey everyone, Matt Covert here again from howtobecomearacecardriver.com and in this video we’re going to talk about something that is a little misunderstood. And we’re going to get right into the nitty gritty, we’re talking about understeer.

And we’re going to start off by talking about kind of how people normally view understeer. Normally people define understeer as when the front tires lose grip before the rear. . .before the rear. OK? And that’s sort of true but it’s not the whole story so let’s just look at this quick example, OK?

So people normally view understeer with a car going this way and perhaps going too fast or a turn in too soon, it just has too much speed to make the corner – not enough grip in the front end, alright? And so what happens is the car tends to just go straight even though the wheels are pointed this way. And you can already see, if you’ve seen the slip angle video. You can see a pretty bad, well, slip angle. And that’s why the car is understeering.

But I want to get a little more technical than that, so let’s look at something that will really open your eyes about understeer. We’re going to get right into the dirty nitty gritty stuff.

OK? Now don’t let this diagram scare you, I know there’s a lot going here but I’m going to take you through the whole thing. I found a similar diagram to this is Skip Barber’s Going Faster book. It’s about mastering the art of race driving, and if you haven’t read that book it’s amazing. There is so much technical stuff in there and I highly encourage you to read that.

But this is something we’re going to talk about really quickly and I’m going to explain all these crazy little lines so don’t get too scared OK? Let’s break it down into little sections. OK? This curving line that goes through the middle of the car, that is that path of the vehicle as it goes around a corner, so that one’s not a big deal, alright? And let’s look at the front slip angle. You’ve seen this before if you saw the other videos, not a big deal. OK? This is the direction the vehicle is going and this is the direction the front tires are pointed and the difference is the slip angle.

You’ve seen that before that’s not new. OK? Let’s take a quick look at the yaw angle. This center line is the center of the vehicle and, what am I trying to say, that’s the direction the vehicle is pointing. Alright. And this is the direction it’s actually going. And we know, because we’ve seen the yaw angle video, that the difference between these two lines is the yaw angle. That’s not too difficult either OK?

So there’s one more component to this crazy looking diagram and that is the rear slip angle and we haven’t specifically talked about rear slip angle yet. One thing that people don’t understand is that rear slip angle are extremely important to how a vehicle handles. People always think about front slip angles because you’re always turning the front wheels et cetera and creating different angles. But for a vehicle to handle optimally, the rear tires have to slip across the surface just like the front ones do. And this plays a big component in understanding how understeer is really happening.

OK? So just like the front end, the rear slip angle is the difference between where the wheel is pointed and the direction it’s actually sliding across the surface. And the difference again is just the slip angle.

So when we’re talking about understeer we’re talking about three separate components, OK? Understeer. . .let me draw out some angles, just theoretical angles. Say we have a fourteen degree, fourteen degree front slip angle, a six degree rear slip angle, and a yaw angle is just four degrees.

This is the real definition of understeer, OK? When the front slip angles are larger than the rear then you technically have understeer. Right? And I know that might seem a little basic but once we get into neutral, a neutral handling car, which is another video entirely, you’ll understand why this has to make sense the way it does. OK?

And when you’re understeering the yaw angle is very very small, it’s almost nothing. Because when your front end is sliding, well the rear doesn’t have a tendency to pop out. So this is the real definition of understeer. Alright? So I’m going to stop there I think and then move onto an oversteer video. Because that’s a little different than this. OK?

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