You’ve bought new shock absorbers (or struts and shocks for most cars) for your diesel, anticipating ride and handling that will be like new, or, with upgraded shocks, better than new. But like most diesel owners, you’ve got a lot of miles on your ride and are concerned that some of what you hear, and feel won’t go away with new shocks alone. What else should you consider?
Shock absorbers are only one of a complex system in your car and truck that keeps the tires on the road and isolates the road from passengers. Don’t overlook these other parts.
There are a lot of rubber bits that keep your suspension in place and operating smoothly, and all of them will wear over time. In higher performance cars these items can wear out relatively quickly, certainly in less than 100,000 miles. Rubber is used in shock and spring mounts, suspension components, and steering systems.
Let’s break down some of the symptoms you may be experiencing, along with their causes, as we show on the table below.
|Odd noises||Clunking on bumps, squeaking while driving or turning, rattling on smallest road irregularities||Worn or incorrectly installed strut or shock mounts, broken spring, worn or rusted strut bearings|
|Poor alignment||Alignment not within spec after shop aligns it, or you’re told it can’t be aligned properly||Worn bushings (especially control arms), strut mounts, rear axle bushings, or shifted front or rear subframe.|
|Tire wear||Uneven tire wear even after new shocks and an alignment||See above, and bent suspension components are also a possible cause.|
|Shake on braking||Pulsation in the brake pedal on moderate to hard braking, especially from highway speeds.||Usually attributed to brake pad buildup or warped rotors, but that’s not always the cause. Could be worn suspension or steering bushings|
Many of the issues symptoms and their causes can be directly related to suspension install components or the suspension itself, along with elements of the steering system. Mounts and buffers, or spring perches, are usually the trouble source in suspensions, and bushings are usually the culprit in suspension and steering. Proper install and alignment are also important, which we’ll touch on a bit later in this article.
What do you look for? And what do you replace? It’s going to vary by vehicle, but let’s look at the big categories: Suspension install and install parts, and suspension and steering parts. We’ve addressed brake issues in a separate article, Why Do Brakes Pulse?.
Suspension Install Hardware
If you’re renewing suspension in a car or truck the pieces required can range widely from few to many. Some cars and trucks (VWs come to mind) just need mounts, bump stops, and perhaps boots to cover the shocks. And new install bolts. But higher priced vehicles (like BMWs) may also need new upper and lower spring pads, strut carrier gaskets, and shock guides. You may or may not want to replace all these items depending on the miles on your car and how it’s been treated. But if you overlook some or all of these components, you may not be happy with the result.
Most modern cars (and a lot of trucks) have front suspensions that include control arms. The simplest suspensions might have one arm on each side, complex ones may have 4, or even more. And to save weight many manufacturers are making control arms out of aluminum. This improves ride and handling, but when bushings wear you typically have to replace the arm. New bushings can’t be pressed in, as they can with stamped steel arms. And many owners replace arms in sets, as the install cost and need for an alignment costs may outweigh the cost of the parts.
Rear suspension may have control arms as well, or a beam axle with trailing links, or a live (or solid) rear axle. Either way, there are bushings for the arms, for trailing links, or for locating arms that can wear. Some of these bushings can be renewed instead of replacing the entire component.
Often when shops struggle to align vehicles properly it’s because of worn control arms or axle bushings. They are also a big cause of uneven tire wear. You can inspect bushings with a bright light, even with the vehicle on the ground. Look for cracking, or bushings that are coming out of its mount. Those are sure signs that they need to be replaced.
Although it’s not strictly suspension, worn steering components can also cause noise, poor alignment, and tire wear. Ball joints and tie rod ends are common culprits, as are inner tie rods. Stabilizer links or bushings can cause a rattling sound when driving.
Wear on these components may be hard to check visually, but alignment shops usually can identify them. You may want to have a shop inspect the car before starting suspension replacement, so you can replace the worn steering components at the same time.
A Note About Alignment
The quality of alignments dealers and repair shops provide varies widely, all the way from “toe and go” where they just set the front wheel toe adjustment, to a much more comprehensive 4 wheel alignment that includes shifting subframes if needed. The range of adjustments available on modern cars vary: Some have adjustable camber and caster, many do not. Toe may not be adjustable in the rear suspension: if a control or trailing arm is bent you may not be able to align the car without replacing that component. Finding a shop that will spend time to get your car right, and will share the alignment report with you, may save you money in the long run in better fuel economy and longer tire life.
Most of us want our vehicles to last. And we want to enjoy every mile. Although inspecting and replacing all the install, suspension, and steering components can cost a little more, it’ll pay you back in a much more pleasant, and safer, driving experience. Diesel on!