Revisiting understeer
May 31st, 2003 by gregr
Frankster left a comment on my previous post regarding understeer and looking where you want to go, and I thought it interesting enough to post here:
“Look where you want to go” does not apply to understeer. You are already looking and steering in the direction you want to go, but it’s not happening because you’ve lost front end traction.
If you continue look in the direction you want to turn and steer that way (around the curve) you will continue or even increase the understeer situation. You need to momentarily steer LESS in the direction you want to go until the front wheels regain traction.
Good point, Frank, I should have been a bit more clear. I didn’t mean you can look where you want to go and you will magically go there without any other actions. Obviously you need to consciously use the throttle, brakes, and steering.
But from a racing perspective, I don’t agree completely with what you’re saying.
In an understeer situation, there are theoretically two ways to correct it – either reduce the steering angle as you point out, or reduce throttle. Let’s look at both of these in more detail.
Reducing steering angle will obviously reduce understeer, and in the Safeway parking lot, this will work great. However, on the track, if you reduce steering angle, you will drive off the track…remember, we’re at the limit here, and we were already planning to exit the curve with about 12 inches or less to spare between the car and the edge of the track. In some cases the edge of the track is dirt, but in other cases it’s a concrete wall. There’s no room to open the steering wheel.
The other option is to reduce throttle. This shifts weight forward, onto the front tires, increasing their grip. Understeer is thus reduced, and the line around the turn tightens. We’ve lost some time by lifting off the throttle, but we’re still on the track. Don’t get crazy with the lift, though, or the car will start rotating – you’ll go from understeer to oversteer in a heartbeat. More on this below.
So what does this have to do with where you’re looking? If you’re looking where you want to go, and lifting off the throttle to keep the car on the track, you will naturally tend to lift just the right amount. Too little, you drive off the track. Too much, you’ve lost more time than you had to. And at the same time, you’re making steering corrections – definitely look where you want to go.
Incidentally, when most folks start understeering, their natural reaction is to lift off the throttle. This is why most street cars tend towards understeer when you drive them off the lot – it’s generally safer for the average Joe in most situations.
Of course, you can also forget the steering correction altogether, and use throttle to kick out the rear
end.
Frank wasn’t specific about how to use the throttle in this case, so let’s look at both possibilities.
First, you could stomp on the throttle. If you have lots of horsepower, you might be able to break the rear end loose, and go from an understeer situation to power oversteer. This could work in some situations, but in most cases at the cornering limit of the car you will bump up against the laws of physics and go flying off the track.
Second, you could lift off the throttle to “kick out the rear end”. Definitely possible – if you do an abrupt lift in mid-turn, the rear end of the car will get very light (remember, all the weight shifted forward) and typically start coming around. The trick here is to get back on the throttle at just the right time and the right amount to get weight back on the rear tires without breaking them loose, or you just might loop it all the way around. That said, a quick lift like this is often a good way to clear up a mild-to-moderate understeer with minimal time loss under racing conditions. I say “under racing conditions” because during qualifying, the lap is probably shot. And on the street, just lift slowly and carefully. :-)
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