How Can I Make My Car Ride Smoothly?by Richard Rowe
New cars handle better than ever before -- which is nice, if you're into that sort of thing. However, while tuning for European handling on benchmark courses like Germany's Nurburgring has yielded some impressively refined corner carvers, it hasn't done much for ride quality. Add to that today's obsession with impractically large wheels on big, suspiciously cheap automobiles, and you've got a recipe for bone-jarring impacts and mind-numbing vibration. No, cloud-like ride comfort reminiscent of an old Rolls Royce might not be everybody's first priority; but for some, it's the only priority that matters.
The Basic Approach
The purpose of a vehicle's suspension is to allow the wheels and tires to absorb the impact of road imperfections before they make it to the chassis, and then to you. A good-riding suspension must be quick to give, to yield to road imperfections. There are two ways to accomplish this. The first is to reduce the vehicle's "unsprung weight," so the suspension moves faster with less force input. The lower the mass of the wheels, tires, wheel hubs and suspension components, the quicker the suspension can respond to imperfections in the road. In practical terms, you want the wheels and suspension light, and the rest of the vehicle heavy. The second is to make the suspension softer, so the wheels can get over those imperfections and absorb impact force before it can get to the chassis. But even then, some shock and vibration will make it to you through the chassis; there are other ways of dealing with that.
Softening the Suspension
This is the go-to approach for most, since it's where the greatest improvements are usually found. The standard approach is to install softer shock absorbers designed for comfort rather than performance, and to follow that up with softer -- "lower rate" -- springs. Comfort-ride shocks aren't usually hard to come by for popular applications, but those seeking the softest possible ride might opt for a set of adjustable shocks or a full air suspension. If you do go for air suspension, look into a set from Praxis, whose patented dual-rate systems will allow you to control ride height and firmness independently. You might have a hard time finding softer springs as direct replacements if you opt to stay with a standard setup. In this case, you may have better luck directly contacting an original-equipment spring supplier like Eaton, and telling the representative what you want.
Wheels and Tires
Low-profile tires and big wheels might look cool, and they can help to sharpen handling, but they're absolute death with regard to ride comfort for several reasons. First, lower profile tires -- "lower aspect ratio" tires -- have stiffer sidewalls, which make the tire harder and less capable of absorbing bumps. Second, big rims themselves are often incredibly heavy, particularly showy solid disc and spinner types. Heavier wheels have more inertia and increase unsprung mass, so they don't want to move when going over bumps. For ride comfort, you want the lightest and narrowest wheels possible, preferably no more than 18 inches in diameter and 7 inches wide. Stay with tall, skinny tires with an aspect ratio of 60 or higher, and cut about 3 to 5 psi off the recommended inflation pressure to give yourself a nice, soft cushion of air. And, whatever you do, stay away from run-flat tires. Modern run-flats are better than older designs, but they're still stiffer than conventional tires.
Further Chassis Modifications
Lightweight suspension and brake components are always helpful if they're available; aluminum, carbon-ceramic and carbon fiber are your best friends here, if those parts are available. Even carbon fiber driveshafts or axle shafts can make a difference, since the driveshaft is part of the vehicle's unsprung mass. Independent-suspension vehicles ride better than those with heavy, solid axles, but this kind of conversion might not be an option for many. Installing thinner or weaker anti-roll -- stabilizer -- bars will smooth out your ride if a wheel on one side of the vehicle drops into a pothole. But this is definitely going to make for an ill-handling barge of a vehicle, particularly if you combine weaker roll bars with softer shocks and springs.
New body bushings -- if you have an old body-on-frame vehicle -- will help isolate the chassis from vibration. Double-stacking an extra set of rubber isolator rings on top of your coil springs can make a difference; slather both of them with a healthy coat of bearing grease to ward off irritating rubber squeaks. Or, if you don't want to stack isolators, at least check to make sure your stock spring isolators are in good condition. To reduce the vibrations that make it through the chassis and suspension, you might opt to install rubber isolator "pucks" in your steering column and driveshaft, if possible. And you'd be surprised how much good a couple of thick strips of rubber between your seat mounts and floorboards will do; but this might be a job best left to a professional, since you don't want to compromise safety.
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