Going Looser is the Most Tempting Trick in Car Setup

(Unless otherwise stated, assume I’m describing a rear-wheel drive car in all scenarios describing throttle application).

Ideally this would begin with a tight definition of oversteer and understeer, or loose and tight, or whatever vernacular you prefer. The entire topic could cover much of what’s discussed in Racecar Vehicle Dynamics, DrRacing’s blog, and my own feelings, for thousands of words.

Broadly, oversteer is when there’s more front grip than rear, and understeer is when there’s less front grip than rear. This definition doesn’t satisfy me, but is serviceable.

Typically, we adjust the balance by adjusting the front and rear roll stiffness. For reasons of brevity, the corner springs and the anti-roll bars. A softer front moves the balance of grip forwards, adding oversteer, a softer rear moves it backwards, adding understeer.

There’s a lot of other adjustments that can have the same effect here, but those are your main ones.

Understeer is stable. You want a car to be stable. Imagine driving a car that never stopped trying to rotate. Where every steering input accelerates the car in that direction. Maybe you could learn how to control that, and figure out how to guide the car back to a yaw rate of zero. But think about how exhausting it would be to race a car where even the straights were tests of steering position.

But too stable and a driver finds the car doesn’t want to turn. Too much stability subtracts command over direction using the wheel. Which, ironically, can reduce stability again. Less front grip means the car doesn’t want to turn as much, so a driver will naturally enter a corner slower and try to accelerate earlier, using the power to help the car rotate. Accelerating earlier means the driver will have more steering lock on, which increases the chances of power oversteer. And because there’s less front grip, it’s now harder to catch the sudden snap. The inverse is also true, where going too unstable can take away all confidence to use the steering properly, so you wash wide.

But within moderation, a less stable car gives you more control over the direction and position on the track, but you’re walking on a finer tightrope. The car is free to move around more. And it feels good, doesn’t it? You can brake later, rotate the car easier while braking. There’s less weight transfer up front so now the front inside wheel isn’t locking so often. Less grip at the rear means the car reacts more immediately to even smaller throttle inputs. A looser car feels like you, the driver, are an expert tracing out the limit of grip, compared to a stable car that reluctantly goes where the steering wheel is pointed, and you nail the throttle and the tyres unsatisfyingly take it.

I’m always so tempted to keep softening the front and stiffening the rear. The car feels more alive, more interesting to drive, and feels more forgiving because I can easily slow down and tighten my line if I miss the corner entry. The racing line widens, somewhat, especially in high speed corners where a comfortably stable car might have less options for trajectories through. But it’s all a fallacy. Appreciating this capability is forging a habit of missing apexes and getting sloppy with my racing line.

And besides, within reason, a less stable car is easier to spin out. And nothing is slower than looping it, or snapping into a barrier. You’re unlikely to find any speed worth racing with in the edgey end of handling balance.

Don’t get me wrong, I’ve done lateral force vs LLTD plots. There is typically more grip in a looser car, especially in cars with wide rear tyres and a rear biased downforce setup to compensate for the mu lost. But it’s important to remember that setup is about optimising the car and giving the driver a tool they feel comfortable in lap after lap, not just creating a bandaid that feels good. Pinning down precisely what that means is one of the key ingredients to a fast setup