Corner weighting the ride heights can help a car turn

Adjusting individual suspension heights can help with cornering. Photo: LiveMedia, Shutterstock.
Adjusting individual suspension heights can help with cornering. Photo: LiveMedia, Shutterstock.

Once you've wrapped your head around the ways a driver can deal with oversteer, understeer and load transfer to affect a car's cornering balance and behaviour with their driving technique, we can look at some more car setup options.

I've mentioned toe settings in one of these columns before (the Ackerman steering story). Briefly though, front toe-in gives straight-line stability and front toe-out gives more eager turn-in. Rear toe-out also helps a car turn, but at the expense of more exit oversteer (which you don't want when chasing a lap time) while rear toe-in adds some rear stability and at the same time tends to induce more understeer. Aggressive toe settings in any direction will also cause excessive tyre heat and wear (which you don't care about in really short events or qualifying, but you do care in longer events or on the street).

That's not all that can be changed for the purpose of making a vehicle more interested in turning and hopefully still clinging onto the road while doing so.

One trick that can be applied on certain cars is corner-weighting (or cross-weighting when thought of diagonally).

This doesn't involve moving ballast around (although you can do that too if you're required to carry some, but for simplicity let's pretend there isn't any), it instead involves manipulating the suspension.

As a concept, corner-weighting is done by measuring the weight (downward force of gravity) under each tyre, and then adjusting the height of the suspension at each corner to change those numbers.

Assuming the vehicle isn't leaning over already, if you raise the height of the left rear for example, you will also increase its corner-weight measurement, as well as that of the diagonally opposite tyre (in this case the right front) a bit too. It will also have an effect on the other two tyres by reducing one or both (but by how much for each will depend on factors like the wheelbase length and track width, and the suspension design).

Overall though, the four weights will still add up to the same number as they did before you changed any of the heights.

For road cars, if your suspension guru offers to corner-weight the vehicle for you, and they make it symmetrical left and right, you end up with a vehicle that feels more balanced, because it wants to turn left and right with near identical enthusiasm and near identical grip (assuming the two compared road corners are just mirrors of each other).

In a race or other form of competition car though, it can actually be done asymmetrically on purpose to help the vehicle turn one way better than the other.

In NASCAR and other oval racing this is often done to help the car turn left (they will raise the rights and lower the lefts to achieve this). Their engineers also make a number of other adjustments which we won't go into.

For some tracks though, you want to prioritise turning right, and our above example of raising the left rear should actually help this. If the rear was already high enough, lowering the right rear instead should also help the car turn right better than it did before the adjustment. (Side note: we're adjusting the rear because the front height is usually determined by the rules or the aero, and will often be about as low as either of those allow).

Explaining why this works though, is just a little more complicated than the load transfer effect that we can apply with the pedals and the steering wheel.

You may remember that driver-induced load transfer places more downward pressure on the front under brakes, more on the rear under acceleration, and more on the outside when turning. Whereas our ride height adjustment has not only changed the weight measurement under each of the tyres at rest, it has also slightly altered the angle of the vehicle in relation to the road.

That means it has also made a minor change to the vehicle's centre of gravity, as well as other things like the body's relationships with (and distances to) the front and rear suspensions' roll centres and what's called the instantaneous centres.

That's something we've run out of room for in this story space though. Just know that the adjusted corner weights themselves aren't the only factor at play here.