One of the most common aftermarket upgrades in the automotive world is a set of coilovers, yet it’s also one of the most misunderstood. While there are certainly very real benefits to lowering a ride, or stiffening a suspension, these benefits are not as clear cut as they may seem. Simply raising the spring rate can rapidly deteriorate not only a vehicle’s comfort, but its handling and grip as well.
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To understand why, first let’s discuss the whole purpose of springs. A suspension has two main jobs: to keep the tires in contact with the road (maintain grip), and to provide comfort to the passengers. If a dip appears in the road, the spring presses the tire down into the dip to maintain traction. If a bump appears in the road, the spring allows the tire to move upward, without the vehicle body moving much, again to maintain grip. So why would a soft spring allow for more grip than a stiff spring?
The simplest way to understand this is to imagine a car with no suspension at all. With no suspension, hitting a bump at speed will result in the vehicle losing contact with the ground. A vehicle with no suspension is essentially equivalent to a vehicle with an infinitely high spring rate. As you decrease the spring rate, the suspension is able to conform better to road irregularities, and thus grip improves. Of course, there is a sweet spot where all of this is optimal, but many aftermarket suspension set ups dramatically spike spring rates over stock specs, and in turn can decrease grip.
While too stiff of a suspension may mean going airborne when hitting a bump, it can also mean not contacting the road quick enough if there’s a drop in the road. Imagine we have a car with a super stiff spring on the front left tire, and a super soft spring on the front right tire, heading towards a 20 millimeter indent ahead where the road drops. Which tire will come into contact with the road first? You might think the higher…