Vehicle manufacturers tune a car’s suspension to give a ‘ride’ or level of comfort versus road holding ability that meets the expectations of the buying public. A Toyota Corolla will always feel softer on the road than a McLaren P1, for example, and the owners expect it to be this way. The vehicle’s manufacturers tend to choose a suspension setting that will suit its intended use and accommodates the variety of road surfaces and conditions that the driver might experience.
Lowering your car is legal, but is it advisable?
What are the advantages and disadvantages of lowering the suspension in your car?
Lowered suspension tends to make a car look slightly more aggressive (up to a point), it can marginally reduce the coefficient of drag, meaning it slips through the air more easily. It lowers the centre of gravity which can allow higher cornering forces due to less body roll (where the suspension on the outside of the corner is compressed due to centrifugal force and more weight is transferred onto those wheels rather than being maintained on the inside wheels).
Why would you avoid lowering your car?
The purpose of your suspension is to keep your tyres in contact with the road while giving the occupants a sufficiently comfortable ride. Vehicle manufacturers spend millions of dollars on testing to get the balance right. Cars that are aimed at drivers that don’t need or want high performance will tend to have a softer suspension setup than sports cars which are inherently more likely to be pushed harder.
On a regular road, softer suspension is often more capable of following the bumps and undulations more effectively than stiffer suspension. Lowering your car means the suspension will need to be made stiffer otherwise there’s a risk that the suspension will ‘bottom out’ – the suspension is compressed to its maximum level. This can cause damage to the suspension components. Stiffer suspension causes the whole vehicle to rise up more, rather than the undulations in the road being absorbed by the suspension. This movement by the vehicle, apart from being less comfortable for the occupants, affects the grip of all other wheels.
Race cars on race tracks can benefit from being extremely low because they use aerodynamic aids to push the vehicle onto the track and the track’s surface is relatively smooth. In fact, if you look at rally cars, they are not particularly low when being driven on road circuits. Aerodynamics, such as spoilers, don’t work at normal road speeds, therefore, there is no advantage in having them.
A lowered car will more easily hit the road surface. It’s common for lowered cars to have issues driving over speed tables and other speed calming measures. Kerbs and roads with extreme camber are a problem. Loading the boot is more likely to cause the exhaust to scrape the ground.
Why would you lower your car?
You want it to look more sporty. This is a perfectly valid reason and many vehicles do look much better when they are dropped an inch or so.
You want a better coefficient of drag, i.e. improvements in fuel economy due to the vehicle being more slippery through the air. The main change you make by lowering the vehicle is reducing the cross-section of the tyre that has to force its way through the air.
You want flatter cornering. Stiffening the suspension reduces body roll meaning that when you corner, the car stays flatter. This can help with tyre wear (although other changes when lowering can make tyre wear worse)
You want better braking and acceleration. Stiffer suspension reduces the weight transfer forwards under braking. Under acceleration, less weight is transferred to the back (good for front-wheel-drive vehicles), but this has to be balanced with the wheels’ ability to maintain contact with the road.